TO UNDERSTAND the state of early intervention for infants and young children with Down syndrome in 1996, it is necessary to consider recent developments within the context of some important historical issues. A few general comments about Down syndrome as a developmental disability are followed by a brief discussion of some of the critical changes that have occurred in our understanding of Down syndrome and in the early intervention field since the 1970s. Investigations on these topics have been conducted by people with training in special education; developmental psychology; communication disorders; physical, occupational, and speech-language therapy; medicine; and others. Each of these disciplines represents a number of theoretical orientations and knowledge bases, as reflected in the diversity of journals in which the materials appear. This variety of perspectives adds depth to our understanding of the development of a child with Down syndrome and the child's family but also challenges attempts to classify and summarize observations and findings.
In this chapter, the phrase early intervention is used to refer to explicit programs of remediation undertaken with babies or young children until school age, or approximately the first 5 years of life. The primary focus is on empirical information about the effectiveness of early intervention for children with Down syndrome. Thus, attention is directed primarily to reports that include a number of children in which the descriptions are sufficiently detailed to permit insight into the nature of the intervention and the participating individuals, in which analyses were conducted with instruments of demonstrated value, and, finally, in which outcomes were reported in ways that permit evaluation.
Down syndrome is a genetic disorder with a prevalence of approximately 1:600 to 1:700 births, is strongly associated with mental retardation, and is usually identified at birth and confirmed by a karyotype showing trisomy of chromosome 21. The additional material of an extra chromosome 21 appears to affect almost every organ system, resulting in a wide spectrum of consequences, some of which are life threatening (e.g., cardiac complications), some of which significantly alter the individual's life course (e.g., mental retardation), and some of which are merely curious characteristics found more often among individuals with Down syndrome (e.g., a crease that traverses across the palm of the hand). It has been known for some time that the phenotypic characteristics of Down syndrome are highly variable; little is known at this time, however, regarding how the triplicated chromosome 21 causes the considerable variability in mental retardation and other characteristics of the syndrome (Hayes & Batshaw, 1993).
In the context of radical changes in the life expectancies and life experiences of individuals with Down syndrome, parents have considerably less certainty than in years past about their child's development, especially in the United States in the 1990s, where "the sky's the limit" is often the polite framework for this topic. The ease with which professionals can identify Down syndrome in even very young children makes possible a sense of solidarity among many families who seem only to share the family characteristic of having a child with Down syndrome. Ironically, during the first few months of life, babies with Down syndrome are less likely to be identified as such by strangers, and parents often seem to experience a "honeymoon" period for the first 6 months or so, reporting that the baby with Down syndrome is "just like" the other children in the family at that age. When the child is wrapped in a blanket and nestled into a parent's arms, it is in fact much more difficult to notice the stigmata of Down syndrome. In addition, parents and others are typically unaware of the subtle differences that differentiate babies with Down syndrome from typically developing babies. In fact, tests of early infancy evaluate many of these babies as "normal" (Shonkoff, Hauser-Cram, Krauss, & Upshur, 1992, pp. 21-22), supporting parental dreams of escaping retardation for their child.
Despite the continuing hope for medical treatments that might dramatically alter the mental retardation associated with this syndrome, no new significant medical treatments have been forthcoming. The primary methods of diminishing the effects of retardation remain psychoeducational working directly with the individual; providing advice, support, and training to adults and others in the immediate sphere; and altering the more distal social and physical environment to increase the roles and activities for which individuals with Down syndrome are suitable candidates. As has been demonstrated for children without Down syndrome, a relationship has been observed between relative success on tests of cognitive performance by children with Down syndrome and their parents' scores on similar instruments (Sharav, Collins, & Shlomo, 1985), which suggests that children's and parents' IQs are correlated. At this time, however, little is known about the relative impact of biological contributions to this relationship and the ways the genetic factors interact with the social and physical environments.
Two particularly important changes have occurred since the 1960s that have influenced attitudes, treatment, and expectations for people with Down syndrome and have important implications for the nature of early intervention for babies with Down syndrome. As most middle-age and older Americans can readily report, there now exists widespread acceptance and support for raising youngsters with Down syndrome at home and having them participate in a variety of activities as part of community integration, rather than placement in institutional settings. A comparison may offer insight into the impact this issue has for early intervention. According to Feigelson's (1990) report, babies with Down syndrome in Israel in the 1980s were being abandoned at such an alarming rate that a program was instituted with a primary focus of encouraging families to take their babies with Down syndrome home with them. Relinquishing parental rights for babies with Down syndrome occurs in the United States but is relatively uncommon.
Second, dramatic improvements in medical care have had impressive consequences, greatly increasing the life expectancy of individuals with Down syndrome (Eyman, Call, & White, 1991). Routine state-of-the-art medical care is now expected for children with Down syndrome, with special attention to their unique medical problems and needs (Hayes & Batshaw, 1993). This includes surgery for those with cardiac defects (about 40%-50% of children); careful monitoring of ear infections, hearing problems, and vision problems, with prompt attention to corrective therapies as needed; and evaluation of a variety of other conditions that may require special medical attention or have implications for caregiving (e.g., hypotonia and joint laxity, hypothyroidism, obesity).
It has become the norm that reviews and discussions of Down syndrome in medical texts and review articles for pediatricians and other physicians now routinely recommend raising children at home; more germane to this chapter, pediatricians and others are urged to refer the infant for early intervention as soon after birth as possible (Hayes & Batshaw, 1993). Indeed, infants with Down syndrome are enrolled in early intervention programs much earlier than other infants with developmental disabilities, usually before 6 months of age (Shonkoff et al., 1992). This pattern of early referral no doubt represents the confluence of both the early diagnosis of Down syndrome, often based on physical signs noted at or shortly after birth, and the widespread belief in the efficacy of involvement in early intervention for infants with Down syndrome and their families.
Within an early intervention program, parents may meet with other parents to share experiences. These groups can provide social and emotional support as parents work through their initial adjustment, in addition to providing an arena for the exchange of information about community services and resources. The national parent movement that advocated for public education for children with Down syndrome and other disabilities, which led to passage of the Education for All Handicapped Children Act of 1975 (PL 94-142), has evolved into a parent-to-parent support network, with local, state, and national organizations. The National Down Syndrome Congress is one such national group, which publishes a newsletter 10 times per year; helps to organize local parent support groups, including in-hospital parent-to-parent support after the birth of an infant with Down syndrome; and holds an annual convention usually attended by several thousand parents, professionals, and people with Down syndrome of all ages to share information and experiences about Down syndrome. One goal of this organization has been to increase public awareness about Down syndrome in order to promote positive attitudes and expectations about people with Down syndrome. The National Down Syndrome Society, also committed to assisting grass roots efforts to improve the lives of those with Down syndrome, has historically been more focused on a research agenda, sponsoring conferences for research scientists.
Mass media have played an important role in informing the general public about Down syndrome and removing some of the prejudicial, outdated, and stigmatizing stereotypes and beliefs about Down syndrome. For example, Chris Burke, one of the actors in a weekly syndicated television drama series, "Life Goes On," is a young man with Down syndrome who portrayed a similar individual as a competent and contributing member of a middle-class family. Such a portrayal was considered by many to be invaluable in shattering negative images about Down syndrome. Commercials on television and in the print media have increasingly included individuals with Down syndrome, increasing their visibility.
Among the stereotypes that are being dispelled are that Down syndrome is a homogeneous condition in which all individuals are highly similar in intellectual, behavioral, and other characteristics and that the expected intellectual, developmental, and functional outcomes are poor. As a variety of research shows, although Down syndrome is an identifiable condition with many characteristics shared across individuals, there is considerable variation among individuals with Down syndrome-medically, physically, intellectually, and psychologically. Likewise, the families of children with Down syndrome vary considerably across all of the dimensions that characterize families (Mahoney, O'Sullivan, & Robinson, 1992). When children with Down syndrome were educated in uniform ways based on the issue of the primary diagnosis, the preferences of families contributed relatively little to programming. In contrast, ideological commitments to integration or inclusion, combined with financial constraints of school districts, are now making segregated settings for children with Down syndrome less common in the out-of-home activity that occupies most of the waking time of children-school. Furthermore, children with Down syndrome are now taking advantage of participation in a wide variety of natural settings (e.g., church, scouting, sports, play groups) uncommon in the past.
In sum, although Down syndrome may have existed for millennia, with phenotypical characteristics similar to those observed throughout the modern-day world, since the passage of PL 94-142, changes in medical treatment and social attitudes have produced significant new challenges to families and professionals who care for individuals with Down syndrome. The upper limits of achievement are not clearly demarcated, inviting professionals and families alike to help young people with Down syndrome to attain new goals. This atmosphere is marked simultaneously by great excitement and almost inevitable disappointment as the child reaches school age and middle childhood and the developmental differences from typical peers become more noticeable.
Infancy has special significance for families with a baby with Down syndrome. This is the most common time for the life-threatening cardiac and other problems to be dealt with surgically, an event that places a family under extreme stress and anxiety. In other ways the first few months present a grace period, permitting families to begin the process of adjusting to their new family member in the comfort of some measure of privacy. The identification of Down syndrome in early infancy also has consequences for the types of goals and objectives that families are likely to see as most important for their child. Communication and language are often cited as the most challenging competencies for individuals with Down syndrome. Yet the developmental accomplishments that are most obvious in infancy (etymologically meaning "incapable of speech") are likely to be motor milestones, with few parents aware of the ways in which preverbal communication leads to the acquisition of language.
TRENDS IN EARLY INTERVENTION: FROM INFANT STIMULATION TO EARLY INTERVENTION
Children with Down syndrome are obvious recipients of early intervention services because of their mental and physical retardation. Generally defined, this means a slower rate of development, lower final level of attainment, and most likely some qualitative differences in how skills are performed or integrated with other behaviors. It is assumed that participation in early intervention can enhance early development and get the child off to a good start in order to reach maximal intellectual and adaptive functioning. The hope seems to be that, if early development proceeds at a faster rate, more closely approximating a typical developmental course, higher final levels of cognitive, linguistic, adaptive, academic, and other skills can be attained. At the very least, researchers acknowledge the presence of a progressive decline in rate of development for children with Down syndrome and expect that participation in early intervention will slow that decline. Indeed, many of the earliest studies of children with Down syndrome claimed positive effects of early intervention by analyses indicating slower declines in developmental quotient (DQ) or IQ for early intervention participants (see review chapters by Guralnick & Bennett, 1987; Guralnick & Bricker, 1987).
An alternative way of conceptualizing the special role of early experiences for infants with Down syndrome emphasizes the importance of initiating the child into a set of experiences and expectations that will optimize the child's inclusion and participation in community activities and relationships. This view can be seen in the commitment some families have shown to create as normal a life situation as possible for their child with Down syndrome, consistent with a view of infancy as a "sensitive period" for determining the general type of life the child will lead. Guralnick (1990) described this intuitive sense of a "good life" in his treatment of the central role of social competence with peers in the lives of young children with disabilities and stated that "understanding and promoting the social competence of young handicapped children may well be the most important challenge to the field of early intervention in the decade of the 1990s" (p. 3). Family members and professionals who share these goals will value activities that make possible the initiation of enduring relationships with peers without disabilities and age-appropriate activities in typical community environments. It can be argued that these pressures put priority on placements in neighborhood child care and nursery settings, often resulting in implementation of therapeutic interventions by individuals with little or no specialized early childhood early intervention training. Despite the apparent attraction of this route, this is an area with little empirical inquiry to date focusing specifically on children with Down syndrome (see Buysse & Bailey, 1993).
The individualized family service plan (IFSP), wherein goals, methods of reaching the goals, and means of evaluating each part of the plan are clearly defined, demands that parents become explicitly aware of their goals for their child with a disability in ways that are rarely required of parents of children who are developing typically. The IFSP, part of the federally mandated provision for infants identified as needing early intervention, is both an assurance of community commitment to helping families with a qualifying child and a visible symbol of the unexpected complexities of parenting a child with Down syndrome. For parents, the process of contributing to and revising the IFSP challenges the frequently heard "common wisdom" that babies with Down syndrome most need to be treated like every other child. Pressures to proceed in a timely way mean that families with an infant with Down syndrome may well be asked to participate in discussions of the child's needs for physical and occupational therapy, speech-language therapy, and broad-based developmental stimulation within weeks of learning of the diagnosis.
Assumptions of Efficacy of Early Intervention
It is generally assumed that early intervention is beneficial for infants with Down syndrome and their families-both in the ways it serves to improve the child's rate of early development and in the opportunities it provides for parents. The latter benefits are presumably twofold, providing particularly helpful companionship to 1) assist the parents in their early emotional adjustment to the birth of a baby with Down syndrome through parent support groups and providing the therapeutic relationship of the early interventionist, and 2) supply professional service and information about Down syndrome. Physicians and other professionals typically have limited experiences with individuals with Down syndrome, increasing the importance of parents acquiring information to share with the professionals. Although the focus of attention remains the youngster with Down syndrome, family members and other care-givers may also need direct intervention to become competent sources of information for others and agents for therapeutic interventions.
The national consensus of the importance of early intervention for children with Down syndrome and their families is reflected in the mandate for states to enroll children and their families in the set of services called "early intervention," independent of information that clearly establishes a set of benefits. An analogy can be made between early intervention for babies with Down syndrome and third grade for typically developing children, such that few would argue that evidence must be aggregated in order to justify a third-grade class. Controversy dominates the nature of the third-grade experience, not the provision of some educational intervention,
Implicated in the complex set of assumptions that support the commitment to early intervention for babies with Down syndrome and their families is the belief by some social scientists and others that the reaction range for mental retardation associated with Down syndrome is sufficiently wide to overlap with typical cognitive capacities, supporting the general belief of engaging in activities that will increase the chance of individuals attaining higher levels of achievement. Consider, for example, the following comment in a discussion of human behavioral genetics from an influential journal in the field of developmental psychology: "Clinical reports of intensive interventions with Down's syndrome children and their families in Israel reveal that treated children can achieve normal intellectual functioning beyond specific skill acquisition and can acquire higher-order cognitive abilities (e.g., bilingual literacy)" (Jackson, 1993, p. 1328) (see also Baumrind, 1993, p. 1302). Solid empirical evidence for such a sweeping statement about typical functioning for groups of children with Down syndrome has not yet been published in peer-reviewed journals or subjected to the scientific scrutiny it deserves.
Following conceptualizations by Guralnick (1991, 1993), "first-generation" research in early intervention dealt with this issue of overall efficacy: Do children who have been enrolled in early intervention differ as a consequence of their involvement in early intervention activities? The prevailing wisdom in society at large is that we have answered that question affirmatively, that early intervention has clear and beneficial effects. Researchers have considered this claim to be sufficiently well established that it is considered unethical to implement a research design that includes a "no treatment" condition (Shonkoff et al., 1992). However, some scholars dispute the claim. For example, Gib-son and Harris (1988), in their review of 21 early intervention demonstration studies for infants with Down syndrome, concluded that evidence has yet to be obtained that children with Down syndrome are better off in early intervention programming than if they were taken care of by "ordinarily prudent parents."
"Second-generation" research deals with a more differentiated view of early intervention, addressing questions about strategies, goals, child and family characteristics, and outcomes of early intervention with greater specificity (Guralnick, 1991, 1993). Included are studies that examine specific types of intervention techniques, curricula, or program factors (intensity, age when program is begun, type of parent involvement); delineate specific child or family factors for comparison; focus on specific developmental outcomes; or examine some combination of program factors, child and family characteristics, and outcomes (what kinds of interventions work well for whom to produce what kinds of outcomes?). Studies targeting a specific type of child (e.g., a child with Down syndrome) could be called second-generation research, regardless of other features of the study.
Longitudinal Studies of Children with Down Syndrome
To place the early intervention enterprise into context, it is important to understand the longer term developmental course and functional outcomes of children with Down syndrome. In one of the few comprehensive long-term follow-up studies of a sample of children with Down syndrome, Carr (1988) described a cohort that originally consisted of 54 infants born in 1963-1964 in London, The original sample comprised 25 boys and 29 girls, observed seven times between 6 weeks and 4 years of age, who were then evaluated again at 11, 16, and 21 years. The original focus of the study was to conduct a developmental follow-up of children who were being raised at home. Over the years, nine of the children had died, most before 4 years of age, and several families were lost to follow-up, leaving a sample of 41 at age 21 years.
The early results showed that DQs declined from a mean of 80 at 6 months to a mean of 45 at 4 years. Mean ratio IQs continued to show declines to a mean of 37 at 11 years, and the results at age 21 years showed a mean mental age on the Leiter International Performance Scale (Arthur, 1952; Leiter, 1979) (a nonverbal intelligence test) of 4 years 11 months, with a range from 1 to 8 years. Notably, the correlation between IQs at 11 and 21 years was .90, showing strong evidence of continuity over the second decade of life in general level of functioning. Additional results focusing on language and academic skills at 21 years showed performance levels with mean mental ages between 4½ and 7½ years on measures of receptive language, expressive vocabulary, reading accuracy and comprehension, and arithmetic. The variability on each measure was considerable. For example, on the reading test used, which has a basal age of 6 years, only two thirds of the children were able to attain the basal age; that group achieved a mean accuracy age of 7 years 8 months, with a mean comprehension age of 6 years 9 months. Likewise, more than three fourths of the group was unable to achieve the minimal score on the arithmetic test (identifying single numbers was the basal skill measured), and the highest arithmetic age achieved was 7 years 11 months. For the entire group, the tested receptive vocabulary ages ranged from 12 to 111 months, with a mean age of 54 months. There was an overall trend for women to perform better than men on the intelligence and educational tests, and for those from higher social class to perform slightly better.
Carr (1988) also reported results about adaptive behaviors and effects on the families. As might be expected, adaptive skills were highly correlated with IQ; almost all the individuals as adults were independent in feeding, dressing, and toileting. In addition, mothers reported that most were easy or fairly easy to manage. The perceived effects of the child with Down syndrome on family life, marital quality, and the siblings were variable, with no indication that there was a pattern of inordinately burdensome stress across most families. Carr also noted, however, that "despite these positive findings . . . these 21-year-olds were not fully independent, could not manage their own lives, were not and would not be self-supporting" (p. 428).
Other longitudinal reports present a somewhat more optimistic long-term picture, indicating considerable variability in later school-age and adolescent cohorts (Crombie, Gunn, & Hayes, 1991; Rynders & Horrobin, 1990). Nevertheless, the actual data presented by these latter authors indicate that the overall mental ages (MAs) of a majority of older children with Down syndrome tend to be at an early school-age level in terms of academic and intelligence tests. Continuing developmental growth through the adolescent years also appears to be the case for at least a subgroup of children with Down syndrome, leading to a recommendation of maintaining appropriate educational goals throughout the school-age period (Rynders & Horrobin, 1990). Using standard parent interview measures such as the Vineland Adaptive Behavior Scales (Sparrow, Balla, & Cicchetti, 1984), several studies have shown that children with Down syndrome show greater lags and impairments in cognitive and communication skills than in personal/social and adaptive behavior (Dykens, Hodapp, & Evans, 1994; Smith & von Tetzchner, 1986). These latter skills are important for more optimal community integration and more optimal care in supervised group care situations in later life, although communication skills are also highly predictive of successful community integration.
DEVELOPMENTAL RESEARCH WITH INFANTS AND PRESCHOOLERS WITH DOWN SYNDROME
Since the 1980s, the growing body of research about early development of infants, toddlers, and preschoolers with Down syndrome has drawn on current trends in developmental psychology and has approached research questions from a developmental perspective. A great deal of this work was summarized in a volume edited by Cicchetti and Beeghly (1990b). Readers are referred to this book for chapters on many developmental topics: temperament; parent-child interactions; attention, memory, and perception; sensorimotor development; self-monitoring; early concept development; language abilities; early communicative and play development; and peer relationships. The importance of this work for the early intervention enterprise relates to the basic question: What is infancy and early childhood like for children with Down syndrome?
An overarching issue addressed in many studies reviewed here is to determine whether the developmental processes of infants and young children with Down syndrome are similar to those of typically developing children but slower in rate or whether there are some qualitative differences in the behavioral expression, patterning, and organization of development (Morss, 1985). Is the sequence and the structure of development the same as or different from that seen in typical children (usually studied by comparing children with Down syndrome to MA-matched typical children)? In a number of developmental areas reviewed in the Cicchetti and Beeghly (1990b) volume, it is concluded that the early sequence of development is similar for children with Down syndrome when compared with children without mental retardation. Following conceptualizations proposed by Cicchetti and his colleagues (see Cicchetti & Beeghly, 1990a), there is also some evidence that many early developmental processes in infants with Down syndrome are coherently organized (e.g., levels of symbolic play behavior are related to MA; early sensorimotor abilities are correlated with affective development). From this perspective, development is defined as "successful negotiations of a series of interlocking social, emotional, and cognitive competencies," and "normal development is characterized by the integration of earlier competencies into later modes of functioning . . . early adaptation tends to promote later adaptation and integration" (Cicchetti & Beeghly, 1990a, p. 32).
Within the social and political climate regarding people with disabilities in the 1990s, it seems that there is a trend away from asking questions about possible qualitative differences between children with Down syndrome and typically developing children. Likely, this attitude has evolved because of the long history of inappropriately low expectations about the developmental possibilities for individuals with Down syndrome (Rynders, Spiker, & Horrobin, 1978). A 1991 essay by Wolfensberger, reflecting on his 30-year career in the field of mental retardation, demonstrates that the treatment and attitudes toward people with mental retardation was truly abominable during much of the 20th century, and indeed in the 1970s and 1980s, and hard-won gains should not be taken for granted. He noted that the positive developments in biomedical knowledge and educational treatments have been particularly helpful for people with Down syndrome. His descriptions of the attitudes of professionals and the public alike remind us that it was not too long ago that people with Down syndrome were considered to be subhuman in many ways.
Perhaps because of this historical context, raising the possibility of developmental differences may be construed by some as a return to discriminatory attitudes and treatment. It has been important to establish commonalities and organizational coherence in the development of children with Down syndrome. Resolving and addressing difference versus delay issues with regard to developmental processes in children with Down syndrome has critical implications for the early intervention enterprise. Strategies and techniques that might be useful to facilitate developmental progress with typically developing infants and children may or may not have similar facilitative effects with children with Down syndrome if the latter children demonstrate qualitatively different learning styles. For example, as is described next, Wishart (1995) has conducted a number of studies of learning in infants with Down syndrome that indicate differences in acquiring and consolidating such basic developmental tasks as object concept. Her findings suggest that, as early as 6 months of age, infants with Down syndrome engage in specific search and exploration behaviors that she describes as "counterproductive" to learning. To ignore these differences, failing to consider their impact on intervention strategies and goals, may mean contributing to new biases that will hinder the very progress that early intervention efforts seek to advance.
In the research since the 1980s, data are presented to show ways in which development in infants and young children with Down syndrome shows some important qualitative differences when compared with development in children without mental retardation and how individual differences are apparent in the first year of life. The types of phenomena studied include information processing and cognitive abilities, social behaviors and social interaction, and language abilities and development.
Dunst's (1990) review of sensorimotor development in infants with Down syndrome concluded that the sequence of development is similar to that of typically developing infants, but the infants with Down syndrome have significant difficulty making transitions from stage to stage, even when their slower developmental pace is taken into account (see also Dunst, 1988). In some of the most interesting work, Wishart (1987) reported data for 3- to 5-year-old children with Down syndrome and children without mental retardation on Piagetian infant search tasks indicating that the children with Down syndrome showed different patterns of performance over a series of trials. She suggested that their object concept knowledge was not well consolidated.
In her summary of a series of studies of children with Down syndrome from birth to age 11 years to investigate cognitive development and problem solving (studies of operant learning, object concept development, and standardized intelligence test performance), Wishart (1993) reported many examples of qualitative learning difficulties experienced by the group with Down syndrome. To illustrate, in operant learning studies, infants with Down syndrome took longer to learn contingencies and seemed more content with noncontingent reinforcement schedules than did typically developing infants. In object concept studies, they showed reduced levels of engagement with tasks they had passed earlier and patterns of developmental instability (loss of performance attained earlier). This seemed to indicate that the acquisition of these skills was not well consolidated. This developmental instability was also noted in IQ test performance over time. Wishart worried that these data indicate a "counterproductive learning style" (p. 400), which results in skill development that is poorly consolidated and therefore developmentally unstable. Duffy and Wishart (1994) have identified a particular learning style associated with Down syndrome, suggesting that these individuals may be distinctively responsive to errorless learning contexts. The implications of these findings for strategies to use in early intervention are not straightforward, but they alert us that generalization of presumably acquired skills to a variety of situations cannot be taken for granted. At the very least, teachers, therapists, and parents engaged in the assessment of skill acquisition might need to pay special attention to how well consolidated and generalizable newly acquired skills are.
Other studies in which information-processing and learning style variables have been considered also indicate special difficulties for children with Down syndrome. For example, Ohr and Fagen (1994) studied contingency learning in a group of ten 9-month-olds with Down syndrome (i.e., arm movements were reinforced with auditory and visual stimulation). Compared with an age-matched group of typically developing infants, the infants with Down syndrome as a group did not learn the contingency, although some individual infants did, and better performance was associated with higher Bayley Mental Scale scores (Bayley, 1969). Such studies are important for early intervention programmers because they shed light on ways in which fundamental learning processes may be impaired and resistant to intervention through conventional strategies. Note that these characteristics are rather subtle and might be missed by even careful observers.
Play Behavior and Attention
A number of studies of play behavior, often emphasizing the development of symbolic play, indicate that young children with Down syndrome are similar to MA-matched typically developing children (see Beeghly, Perry, & Cicchetti, 1989, for a review). Other work on exploratory play has revealed a number of qualitative differences in young children with Down syndrome. Ruskin, Mundy, Kasari, and Sigman (1994) studied object mastery motivation in forty 2-year-olds with Down syndrome and 26 MA-matched typically developing children. The children with Down syndrome were less engaged in the motivation tasks, with shorter sequences of goal-directed behavior and more frequent toy rejection and with less causality pleasure when exploring objects (i.e., not as much positive affect associated with seeing how a toy works or discovering cause-effect relationships).
Legerstee and Bowman (1989) reported data on eight infants with Down syndrome observed from 8 to 48 weeks of age indicating that these infants' social responses showed delays that correspond to delays in cognitive development, but they also showed atypical responses related to a lack of wariness or distress when presented with a still face from an adult. Ruskin, Kasari, Mundy, and Sigman (1994) also studied the deployment of attention to toys and people in their visual field in the groups of typically developing children and children with Down syndrome described previously. Results indicated that the two groups deployed attention toward adults similarly when left to play alone with toys. However, in a social situation, the children with Down syndrome had a more focused style of attention, whereas, in the play alone with toys situation, they smiled less and rejected the toys more often. The authors suggested that the results argue for presenting learning materials in a more lively rather than passive format to young children with Down syndrome in order to engage attention maximally to the materials.
Similar findings have been reported by Loveland (1987), who studied the responses of 32 preschoolers with Down syndrome to their mirror images. She found that the children with Down syndrome explored and deployed attention toward the different mirror tasks presented somewhat differently than did MA-matched typically developing children. For example, the children with Down syndrome tended to maintain high interest in the mirror in situations in which typically developing children lost interest easily, perhaps indicating a failure to habituate in a situation in which such a response is common. These results underscore the value of looking at sequences of events in seeking to increase our understanding of similarities and differences among groups of children. As Wishart (1995) has noted, based on her studies on early learning in young children with Down syndrome, developmental instability may not be sufficiently noted without longitudinal studies in which the same children are observed and assessed repeatedly.
Attachment and Temperament
Studies of attachment and temperament also showed both similarities and differences between children with Down syndrome and typically developing children. Vaughn, Contreras, and Seifer (1994) compared maternal rating of temperament on two instruments for 32 children with Down syndrome and 44 typically developing children over the 12- to 36-month developmental range. Although there were some group differences, many similarities were found: The mean temperament subscale ratings were similar for the two groups, and, across an average of 15 months (time 1 to time 2 assessments), mothers in both groups rated their children as, on average, being easier temperamentally at time 2.
In a study of attachment with 138 young children with Down syndrome using the Strange Situation assessment paradigm, Vaughn, Goldberg, et al. (1994) reported that this measure may not be appropriate for this population. Specifically, a high proportion of the children with Down syndrome were difficult to classify with this measure, resulting in an excess of cases classified as "insecure." In addition, there were marked differences in interactive behaviors in the Strange Situation for the children with Down syndrome as compared with earlier reports of samples of typically developing children. The authors suggested that the stress experienced by the children with Down syndrome in the Strange Situation is functionally different from that experienced by typically developing children.
Although the major focus of discussion by the authors was about this procedure and its use to measure attachment in atypical populations, another conclusion from the data is that the patterning and possibly development of attachment is different for children with Down syndrome. Certainly the reduced arousal of many infants with Down syndrome may affect their behavior toward their parents and the parents' responsiveness toward them. These results may tell us that many young children with Down syndrome are less "readable" in terms of the social, emotional, and communicative cues they emit in social interaction situations. If one also assumes that the early months of life of an infant with Down syndrome include interactions with parents who may be in the process of coming to terms with their child's disability, and many infants have serious heart problems often requiring major surgery, it is certainly possible that the development of secure attachment may be at risk in this population.
Much of the 1980s and 1990s research on parent-infant and parent-child interactions with children with Down syndrome has revolved around this theme of the "readability" of infants and young children with Down syndrome. Underlying this interest is the belief that the parent-child relationship is critical for the child's development, and there is hope that a greater understanding of the optimal strategies for social interaction will contribute the necessary knowledge base for developing optimal intervention strategies. A number of reviewers of the research literature about parent-child interactions with children with Down syndrome have concluded that infants and young children with Down syndrome may be more difficult and less gratifying as social partners, taking less initiative, responding and initiating interactions in a less contingent and predictable manner, and giving social and communicative signals that are less readable (Berger, 1990; Fischer, 1987; Marfo, 1990; Mitchell, 1987; Richard, 1986; Spiker, 1982, 1990). Once again, it appears that these findings about developmental differences may not be widely known or acknowledged by early intervention practitioners or parents who may be promoting a well-intentioned view that babies with Down syndrome are "just like normal babies, only a little slower."
Indeed, some of the work in this area supports these conclusions regarding differences. Hyche, Bakeman, and Adamson (1992) studied mothers' reactions to the "readability" of videotapes showing infants with Down syndrome and typically developing infants, MA-matched for 7, 10, and 16 months and found that "readability" improved with increasing age regardless of infant status, but the youngest children with Down syndrome tended to give social signals less clearly and less frequently than MA-matched typically developing children. Jasnow et al. (1988) concluded that there was less contingent coordination in terms of vocalizations during social interaction for a sample of 4-month-old infants with Down syndrome compared with infants without developmental delays, although such lack of coordination was not as obvious at 9 months of age. Similar findings have been noted about early vocal coordination by Stevenson, Leavitt, and Silverberg (1985) and about joint attention by Landry and Chapieski (1990).
Prelinguistic intentional communication behaviors of infants with Down syndrome and MA-matched typically developing infants were examined by Hopmann and Nothnagle (1994b). During free play with their mothers, the infants with Down syndrome used more of their communication acts for social interaction purposes and fewer with the purpose of establishing joint attention. However, the groups produced similar proportions of acts to regulate the mothers' behavior. Differences between the groups were not evident during a high-structure setting, when acts to regulate an adult's behavior dominated both groups' intentional communications. In the structured setting, however, the typically developing infants produced many more communications.
These kinds of child differences have led many researchers to ask two related questions:
It has been shown that mothers of young children with Down syndrome often adopt a more active, directive style, and some authors suggest that this is an appropriate stance given the child interactional differences (e.g., Marfo, 1990, 1992). One unresolved issue relevant to this suggestion is whether parents can have a directive interactional style that is also responsive to the child's ongoing activity and attention.
- How might such differences affect parent behaviors and styles during social and communicative interactions?
- What would be an interactional and communicative style for parents to adopt to promote optimal child development?
Crawley and Spiker (1983) raised this issue, and it continues to be a topic of inquiry in work by Tannock (1988) and Landry, Garner, Pirie, and Swank (1994), among others. Tannock studied mother-child free play interactions of 11 preschool-age children with and 11 children without Down syndrome. She found greater control in terms of maternal directiveness on most measures coded for mothers of children with Down syndrome, but their children were also frequently passive in their interactions. Landry et al. found that interactional characteristics varied with the type of situation. In a comparison of 28 children with Down syndrome who were 30-69 months of age and 28 MA-matched typically developing children, they found that the children with Down syndrome had greater compliance with maternal requests that were directive rather than suggestive but only in a structured situation.
Maurer and Sherrod (1987) conducted a longitudinal study of parent-child interactions in six families with a child with Down syndrome and four families with typically developing children over a 2-year period beginning when the children were 12 months old. Relevant to this discussion was their finding that, compared with mothers of typically developing children, mothers of children with Down syndrome tended to be less likely to issue a directive when they did not have the child's attention but more likely to issue a directive following child noncompliance. These kinds of studies, with detailed analyses of communicative strategies and their effects during interactional situations, can serve as an important empirical basis for more informed intervention techniques and strategies. In Marfo's (1990) review of the literature about maternal directiveness with young children with disabilities, he cautions that it is premature to conclude that the reduction of maternal directive behavior should be a goal of early intervention work. Furthermore, there is still much to be learned about the relationship between directiveness and responsiveness as separate dimensions of interactional styles, as well as associations between interactional styles and child developmental outcomes.
In a series of analyses of interactions between mothers and their young children with mental retardation, mostly children with Down syndrome, Mahoney (1988) isolated what he believed to be a dysfunctional pattern characteristic of these dyads. Mahoney speculated that this interaction style, in which each ignores the vast majority of the other's attempts to interact, may be the result of parents being taught highly directive interaction styles by early intervention personnel.
In a subsequent analysis of mother-child interaction style in which dyads with a child with Down syndrome were compared with developmentally matched dyads with a typically developing child (Mahoney, Fors, & Wood, 1990), interesting differences were found in the mothers' styles of engaging their children in conversation. Specifically, the authors implicated an orientation of many early intervention programs, the "instructional intent theory," which encourages parents of youngsters with developmental disabilities to be vigilant in their attempts to extract the highest possible level of skill as often as possible. The worry is that such an orientation will not be simultaneously responsive to the child's initiations, will lead to an intrusive parental style, and will be detrimental to developmental progress. Crawley and Spiker (1983) have reported that a parental style of moderate directiveness coupled with responsiveness to child behavior does occur with young children with Down syndrome and was found to be associated with higher DQs.
All of these findings about difficulties in "readability" of infants with Down syndrome and in joint contingent interactions have important implications that may not be sufficiently appreciated in current early intervention practice. For example, if early learning is promoted optimally when the infant is an active initiator and parental behavior is responsive to infant initiatives and encourages active exploration, then an understanding of the possibly different dynamics operating as a result of different infant characteristics is important. However, based on the state of our knowledge in 1996, the strategies or techniques we should recommend to parents are not at all straightforward.
Language and Communication
Chapman (1995) provided an excellent review of research about language development in children with Down syndrome, noting that the same basic questions have persisted since 1970:
Studies continue to ask, 1) is there evidence of specific language deficit in children with Down syndrome, relative to nonverbal cognitive achievements? 2) is there a particular pattern of language strengths and weaknesses (a "profile") characteristic of language acquired by children with Down syndrome? 3) what is the developmental course of language? Is its course best characterized as delay, or atypical acquisition? 4) what degree of individual variation exists in development, and what are its predictors? What are the underlying causes of specific language impairment? (pp. 641-642)
Other reviews concerning language development in children with Down syndrome (e.g., Pruess, Vadasy, & Fewell, 1987; Rondal, 1988) have noted considerable individual differences in the acquisition and use of language. It has been noted that the early acquisition of single words and two-word phrases as well as early grammatical morphemes (e.g., the verb affix -ing, the possessive -s, regular and irregular past tense of verbs) is highly correlated with measures of overall nonverbal MA, similar to that seen in typically developing children (Oliver & Buck-ley, 1994; Rutter & Buckley, 1994). Mervis (1990) concluded a review of research on early conceptual development by noting that studies of the relationship between maternal linguistic input and rate of early vocabulary development in children with Down syndrome have yielded generally weak associations, but she suggested that a stronger association might exist if "semantic contingency to the child's behavior" (p. 292) is examined. Difficulties in nonverbal communication have also been noted in studies (Legerstee & Bowman, 1989; Mundy, Sigman, Kasari, & Yirmiya, 1988). The implications for early intervention are that linguistic input should involve attending to the child's ongoing behavior, commenting on and repeating the child's verbalizations, and generally attempting to ensure comprehension and promote dialogue. Such suggestions must be carefully tested in future studies.
As for long-term language outcomes, Chapman (1995) noted that later vocabulary acquisition continues to develop more slowly, but differences from MA-matched typically developing peers are evident in older children and adolescents in the functional use of their vocabulary in narratives. Fowler (1990) concluded that most individuals with Down syndrome fail to acquire language structures beyond an early preschool level, with impairments seen in syntax, morphology, comprehension, and production. She also concluded her review by noting that there is no evidence for the superiority of any one instructional strategy over any other, perhaps because the causes of the language delays are still largely unknown.
EFFECTIVENESS OF EARLY INTERVENTION
As this review of the early intervention research with children with Down syndrome indicates, there have been several promising developments since the 1980s, all in need of further examination and empirical work. There has been a good deal of theorizing about the benefits of specific intervention models, particularly in relation to developmental research and theories about prelinguistic communication, language development, and parent-child interactions, but the actual intervention efficacy studies are limited. There is also a paucity of research on several important second-generation issues, including
In the remainder of this section, this review of early intervention efficacy research is organized according to the specific outcomes of intervention, the program models, or both. These include intervention effects on overall and cognitive development, language and communication intervention studies, alternative communication studies, studies to promote parent-child interaction, treatments to improve motor and physical development, and effects of inclusion in integrated settings.
- The effects of program duration and intensity
- How individual differences among infants with Down syndrome (e.g., degree of hy-potonia, presence of cardiac defects or hearing losses) and among families relate to program efficacy
- The effects of programs in integrated settings on young children with Down syndrome
Intervention Effects on Overall and Cognitive Development
The earliest early intervention programs for infants and young children with Down syndrome were several university-based demonstration programs begun in the 1960s (Hay-den & Dmitriev, 1975; Rynders & Horrobin, 1975). At that time, there was a growing trend for families with a newborn infant with Down syndrome to take the infant home rather than consider institutional rearing, although there was by no means a general optimism that home life, educational interventions, and community integration could have significant positive effects on the developmental outcomes of such children. The first generation of early intervention research sought to document overall global effects of such programs on infants and young children with Down syndrome.
Short-Term, Long-Term, and Replication Studies There have been several fairly comprehensive review articles about early intervention with children with Down syndrome. Their tone and conclusions have been cautiously optimistic at best. Perhaps the most pessimistic in tone was that of Gibson and Harris (1988), who published results of a meta-analytic review of 21 early intervention programs for children with Down syndrome. The studies reviewed from peer-reviewed journals were conducted with children born largely in the 1960s and 1970s. Gibson and Harris concluded that, on the whole, there was support for short-term benefits of early intervention on developmental rates, most consistently for fine motor and adaptive skills, and on overall DQ/IQ, with fewer and less consistent improvements in linguistic, cognitive, and gross motor skills. The authors were less optimistic about the longevity of the benefits in terms of lasting gains in language and cognitive development. That is, there was no strong evidence to support the contention that intensive early intervention promoted later enhanced school-age performance. Furthermore, these authors drew the following quite pessimistic conclusion to challenge early intervention designers and researchers:
It is not established that DS children reared in the home by ordinarily prudent parents achieve less in the longer term than do at-home DS children also exposed to intensive formal intervention programmes from infancy and into the preschool years, (p. 13)
Although not as pessimistic, authors of several other review articles dealing with early intervention for children with Down syndrome have also concluded that short-term benefits seem to be apparent, but the methodological quality of much of the efficacy research is weak (Harris, 1988; Naganuma, 1987). Harris's review focused on studies of neurodevelopmental therapy (occupational and physical therapy services) not exclusively for infants with Down syndrome, whereas Naganuma reviewed several research projects published since 1975 about early intervention with infants with Down syndrome. Both concluded that methodological confounds prevented drawing conclusions about the impact of early intervention on developmental progress.
Other published work, since 1985, suggests slower progress of infants with Down syndrome compared with those with other disabilities or delays, with declines in overall developmental measures over time (Holmes, Britain, Simpson, & Hassanein, 1987). Piper, Gosselin, Gendron, and Mazer (1986) presented longitudinal data for 32 infants with Down syndrome enrolled in an early intervention program for the first 2 years of life and evaluated at 6, 12, 18, and 24 months. On the Griffiths Scale of Mental Development (Griffiths, 1954), declines in rate of progress were found in all domains measured; the least severe declines were in the personal-social, hand-eye, and performance subscales, essentially social and adaptive behavioral domains, with mean scores decreasing from the 80s at 6 months of age to the 50s-60s by 24 months of age.
Several groups of researchers who designed and evaluated the effects of some of the earliest early intervention programs for children with Down syndrome have published long-term follow-up data about these children as they reached school age and adolescence. Connolly, Morgan, Russell, and Fulliton (1993) compared a group of 10 adolescents who had participated in early intervention in Tennessee with 10 age-matched adolescents who had not. They reported that the early intervention subjects had significantly higher scores on measures of cognitive abilities and adaptive behavior than did the comparison subjects. The mean IQ of the early intervention group was 40.1 compared with 30.5 for the comparison group, with IQ ranges of 25-53 versus 17-45, respectively. Mean social quotients, based on the Vineland Social Maturity Scales, were 60.2 versus 35.7 for the intervention and comparison groups, respectively, with ranges of 34-96 and 21-61, respectively. Distributions of varying levels of mental retardation favored the early intervention group, with many fewer children in the early intervention group being in the severe and profound range. Interpretation of these data are confounded by attrition, because this early intervention sample represents only one quarter of the original sample, and by the fact that the comparison group subjects, although matched for chronological age at time of testing, were on the average 8 years older. Therefore, this represents an older cohort likely to be dissimilar in terms of educational and other community experiences.
Other reports have provided additional data for children with Down syndrome who participated in the outreach sites of the Model Preschool Program at the University of Washington (Fewell & Oelwein, 1991; Oelwein, Fewell, & Pruess, 1985). The original Model Preschool Program was developed for young children with disabilities, including those with Down syndrome, with the goal of increasing the children's rate of development in six areas: gross motor, fine motor, cognition, receptive language, expressive language, and social/self-help skills. The program also sought to involve parents in the instruction of the children. Beginning in 1983, this program was expanded to a number of outreach replication sites in the United States. In the Fewell and Oelwein report, the authors presented results for a group of 194 children, 92 with Down syndrome, from 14 different sites. The original program model was replicated at the outreach sites, and there were also varying degrees of integration with typically developing peers at some of the outreach sites. The assessment measure developed for this study was the Classroom Assessment of Development Skills (CADS) (Oelwein, Fewell, & Pruess, 1988), a curriculum-based assessment with 288 items ranging from birth to 8 years, tapping the six developmental domains listed previously. Also included at five sites was the Battelle Developmental Inventory (BDI) (Newborg, Stock, Wnek, Guidubaldi, & Svinicki, 1984).
The outcome assessments involved a measure of progress or rate of development: the child's developmental age at posttest minus the child's developmental age at pretest divided by the number of months in intervention. The child's pretest rate of development was then compared with the rate of development during the intervention. The analyses of the CADS indicated that, for the group of children with Down syndrome, significant progress was made in all areas except for gross motor. On the BDI, significant improvements were found for the cognitive, personal-social, and adaptive domains but not for the two language or the two motor domains. The authors noted that the CADS measure, with more items than the BDI, was linked to the curriculum, whereas the BDI was a more independent test. Thus, the better results with the CADS, particularly for language areas, may be partially due to "teaching to the test." In addition, many of the CADS examiners were also the children's teachers, introducing unknown biases. Finally, without a control or comparison group, it is really not possible to attribute developmental progress unambiguously to the program instruction per se. Maturation or other factors may have accounted for some of the progress, and other instructional models may have produced greater gains.
Foreign Efficacy Studies Several other reports of non-U.S. samples used either the Griffiths Scale of Mental Development or the Bayley or Binet scales to evaluate early intervention efficacy. Neser, Molteno, and Knight (1989) used the Griffiths scale to measure developmental progress of a group of 55 preschool children with Down syndrome from South Africa. As with many other studies, they found a decrease in DQs with increasing age, with language areas most impaired. Although this was not a study of the effects of early intervention, a comparison of those children in a play group or preschool center with those cared for exclusively at home showed that those in the former group had significantly higher scores on subscales measuring personal-social and nonverbal performance, but no group differences on fine or gross motor or language subscales.
Sharav and Shlomo (1986) reported Bayley and Binet DQ/IQ scores for a group of 51 children with Down syndrome living at home in Jerusalem who participated in an early intervention program that was home based for the first 18 months of life and center based from that time on. By comparing the children's scores with samples from earlier published data (e.g., see Carr, 1988), the authors concluded that the expected declines in developmental levels were reduced for this group of children. Specific detailed program descriptions were not provided for either study.
Effects of Program Intensity One important issue addressed in second-generation research about early intervention is that of differential outcome effects as a function of program intensity. Few studies of this issue exist for the population of children with Down syndrome. One example of an attempt to examine intensity of program participation is a study by Sloper, Glenn, and Cunningham (1986). In this examination of a sample of 24 British infants who had participated in a home-based program since birth, the rates of acquisition of sensorimotor skills were compared for an intensive parent training group (ITG) (n = 12), beginning when the infant reached a Bayley MA equivalent of 7 months, and a less intensively treated control group (CG) (TO = 12), whose parents received "general guidance on early stimulation" (p. 151). The mean ages of the ITG and CG children at the beginning of the study were 41.4 and 43.5 weeks, respectively. Children in the ITG acquired object permanence, imitation, and attention span skills earlier than did those in the CG (as assessed in the homes by presumably nonblinded evaluators). Longer term, more generalized effects were not evident, however, in that from about 20 months of age on, after the intervention was completed, the mean Bayley or Binet scale MAs of the two groups were similar (e.g., at 2½ years the mean MAs for the ITG and CG children were 18.7 and 19.1 months, respectively; at 4 years, they were 31.9 and 32.6 months, respectively). Thus, as summarized by Gibson and Harris (1988), some evidence can be found for the effects of early intervention in accelerating early sensorimotor development, but the import of such gains for longer term continued developmental progress is not impressive.
A related and well-designed replication of a study by Morss (1983) was carried out by Wishart (1986), in which she examined the effects of an object concept training program on a group of 10 infants and toddlers with Down syndrome. An interest in object concept development is based on the developmental assumption that acquiring a mature object concept is a prerequisite for language development, and object concept is viewed as the prototypical cognitive achievement of infancy. Drawing on earlier object concept research indicating that infants with Down syndrome develop more slowly in object concept acquisition compared with typically developing infants, Wishart used a training procedure similar to that of Morss and found that overall performance of the infants with Down syndrome could be improved. She discovered an interesting feature of the search behavior of the infants with Down syndrome, referred to as "switching out," that has not been reported for typically developing infants. During the course of repeated testing trials in which the infant was expected to search for a hidden object, a number of these infants ceased to cooperate or search, even though they could be reengaged later when a different hiding task was presented. The author discussed this behavior as a withdrawal, a cognitive style that may be an early indicator of a motivational or exploratory style that is less than optimal for development.
Descriptive Study Results Shonkoff et al. (1992) published a monograph describing a longitudinal study of development in 190 infants and their families after completing 1 year in early intervention services. From 29 different programs in Massachusetts and New Hampshire, children from three diagnostic groups were selected: Down syndrome (n= 54), motor impairments (n= 77), and a group with etiologically unknown developmental delays (n = 59). The report was a descriptive study, taking a transactional and ecological approach with a variety of child, parent, and family measures completed at baseline and as outcomes, with measures of services being the predominant mediating variables. Causal relationships regarding particular services cannot be derived from such a study, and many of the analyses did not consider diagnostic category, making it impossible to draw conclusions about Down syndrome per se. Regardless, the authors drew several conclusions relevant to the topic of this chapter:
- The infants with Down syndrome and their families began enrollment in early intervention earlier than those in the other two diagnostic groups, usually at less than 6 months of age.
- At baseline, compared with the other two groups, the infants with Down syndrome were classified as having mild delays based on the Bayley Mental Scale. This creates an erroneous prognostic impression, because many young infants with Down syndrome score relatively well on an assessment like the Bayley scale, with inevitable declines and subsequent test scores in the mentally retarded range.
- Child growth in the four areas assessed in this study (overall mental development, play, adaptive behaviors, and interactional behavior with the mother) was quite variable even within the Down syndrome group. For all three diagnostic groups combined, initial level of severity of disability (Bayley Mental Development Index) predicted degree of change (the children with the most severe disabilities showed the least developmental growth). Furthermore, because severity of child disability was positively correlated with intensity of services received, no definitive conclusions can be drawn about early intervention efficacy.
- Degree of participation in parent groups was greatest for mothers with a child with Down syndrome and those with children with more severe disabilities.
- For the sample as a whole, improvements in mother-child interactions were associated with greater child developmental gains, but no causal attributions can be made.
- As Sameroff (1992) concluded in his commentary about this monograph, perhaps the important feature of this study was its attempt to take on "the study of behavior in context" (p. 154). He also noted that this study did not address efficacy questions and at best provides weak support for the contention that early intervention participation produced beneficial effects for children and families.
Language and Communication Intervention Studies
Given the widespread acknowledgment that the development of language and communication is particularly problematic for children with Down syndrome (Chapman, 1995), one would expect to see a good deal of research focusing on specific intervention strategies aimed at facilitating and remediating problems in this area. This is an area in which there are significant individual differences among children, as indicated by a review concluding that first words are acquired between 6 and 84 months and sentences between 17 and 132 months (Gunn, 1985). A systematic review of research litera-ture reveals a number of articles with descriptions of conceptual models for early intervention but limited empirical data from implementation of specific language stimulation programs with the population of infants with Down syndrome. Several models are promising but require more empirical study to validate their benefit. For example, Swift and Rosin (1990) described an intervention perspective for improving speech intelligibility with children with Down syndrome. They posited that their remediation sequence is based on a developmental framework. However, no data are presented about the effects of any of the suggested techniques.
Functional Communication In a review chapter about facilitating speech and language skills in children with Down syndrome, Miller (1988) outlined several basic principles for intervention strategies that are based on a model of language development that emphasizes fostering communication. The goal is reciprocal communication that is used in everyday life in a functional way. Specific intervention strategies are not described in this report, but there are examples of attempts to adopt a functional perspective. For example, Blackbourn and Bankston (1989) described a single case study with a 14-year-old girl with Down syndrome focused on teaching functional language. Improvements in the use of functional expressive language from a mean length of utterance (MLU) of 1.3 to MLUs of 4.4-5.1 ineveryday settings were found after a training program consisting of "direct expansions during the pragmatic activities of social conventions already in the subject's repetitions" (p. 1138). Although this very brief report involved only one older girl, with few details about the training program, it suggests that a focus on functional skills aimed at improving communication in ecologically relevant environments may be a beneficial strategy for young children as well.
Parent-Child Communicative Interactions Dodd, McCormack, and Woodyatt (1994) conducted a parent training program to improve the articulation abilities of nine preschoolers with Down syndrome. These researchers posited that there would be individual differences among parents in terms of the nature of their communicative interactions with their children and that these would be correlated with the children's abilities and progress in the training. In a series of twelve 3-hour parent training sessions by speech-language pathologists, parents received instruction about communicative interactions focusing on listening and giving feedback to encourage consistency of word production, in addition to having time to talk with each other under the guidance of a psychologist about a wide range of issues that concerned them. Videotapes of various types of interactions were used to illustrate techniques to observe and enhance communication. Although there appeared to be an emphasis on pronunciation, the brief descriptions of the training program contained in this report suggest that this program emphasized principles and techniques derived from the basic research about the communicative processes of early language acquisition (e.g., turn taking, functional usefulness of speech, contingent responsiveness in interactions, feedback involving imitation).
To examine the effects of the training program, the children's speech was videotaped and phonetically transcribed, and parental communicative behaviors were rated. Improvements were reported for some of the children in terms of consistency of word productions, but these are difficult to interpret because of the sample size, the change measures used, and the somewhat short pretest-posttest interval. Perhaps more important were comparisons of parents' behaviors at baseline, at mid-program, and at postprogram. For most parents, there were improvements in ratings of their responsiveness to the child's speech and interactional behaviors presumed to facilitate communication (e.g., responsive to child's lead, models clearly, matches child's communication intent). Although the authors reported significant correlations between more optimal parent communicative behaviors and the children's phonological abilities at program end, they did not unambiguously demonstrate any causal relationship because this small group of children had considerable variation in verbal level and output at both baseline and posttraining. More of this kind of focused research aimed at examining specific program effects on specific language, communicative, and social interactional behaviors is sorely needed. Moreover, further study of those children who made little progress with such interventions should be conducted, lest we conclude-most likely erroneously-that deficiencies in parental input are the critical causal mechanisms.
A report about the Hanen Early Language Parent Program illustrates an intervention program model based on perspectives about early language development (Girolametto, Greenberg, & Manolson, 1986). In this article, the authors described the content and process of a "child-centered, conversational model of language intervention," based on the assumption that early language learning "involves joint problem-solving by parent and child" (p. 367). The goal of the program was to develop dialogue skills that involved the adult being responsive to the child's cues to facilitate communicative intent. This began with the earliest social interactions and proceeded through the acquisition of gestures and speech used to convey meaning to communicate. The authors proposed that data on young children with disabilities indicated that they had special problems in developing dialogue skills related to difficulties alternating turns and initiating interactions, and their adult caregivers found it difficult to engage in dialogue with their children because of these characteristics. In many ways, the core difficulty was one of contingent responsiveness. It is assumed that language and communication development is enhanced by contingent interactions, particularly those involving child-initiated topics, and that this is more difficult with children with developmental delays. The remainder of this excellent article describes specific details about the structure, activities, and principles of this program to teach dialogue skills.
Tannock, Girolametto, and Siegel (1992) reported outcome data from a randomized intervention study focusing on "reciprocal social interaction" using the Hanen Model with a sample of 32 mothers and their preschool-age children with developmental delays, nine of whom had Down syndrome (three in the experimental group and six in the control group). It is not possible to draw any conclusions about the program effects on the children with Down syndrome, but the authors noted that the overall results indicated that the mothers in the experimental condition became less directive and more responsive and provided clearer linguistic signals to their children. Moreover, the experimental children showed higher frequencies of vocal turns during interactions. No group differences were found in parent-reported language and communication development of the children. A 12-week program may be too short a time period to obtain significant changes on the measures used, especially for children with developmental delays. Longitudinal research with frequent measures taken should become the norm in the future if we are to evaluate language interventions effectively. This study presents an admirable model of the use of existing empirical data as a source of hypotheses about intervention approaches and of the attempts made to define and evaluate parent-child interactional outcomes.
Another similar type of program and evaluation was reported by Weistuch and Lewis (1985). The Language Interaction Intervention Program is based on the assumption that parents' interactional styles affect the child's language acquisition and on data suggesting that mothers of young children with developmental delays may need help learning how to facilitate language acquisition (i.e., to be more contingently responsive; to use appropriate modeling, expansions, repetitions, and extensions of child vocalizations and verbalizations). Data were reported for 10 typically developing children and 10 children with Down syndrome who were at the 1.0- to 1.5-MLU stage of language development, with mean ages of 22.1 and 42.1 months, respectively. Half of each group was randomly assigned to intervention, consisting of 8 weekly 2-hour workshops about language and communication. Pretest and posttest data consisted of analyses of video-taped mother-child interactions. Mothers in the intervention group increased the amount of interaction time in which they referred to the ongoing context when compared with control group mothers. Relative to control mothers, they also used more syntactic expansions and increased their rates of topic extension, strategies thought to promote language development. No data were presented about effects of the program on the children with Down syndrome. Thus, it is not known whether the changes in maternal behaviors were associated with improvements in child language. Somewhat ironically, Fischer (1988) demonstrated an increase in the revision behaviors of two children with Down syndrome by having their mothers decrease their very high rate of contingent responses.
Prelinguistic Communication Given the increase in basic developmental research about prelinguistic communication and evidence of difficulties in this area for infants and preschoolers with Down syndrome, one might expect that there would be examples of specific intervention programs aimed at facilitating prelinguistic communication skills or behaviors. Only recently have a few research studies appeared in the peer-reviewed literature, all with very small sample sizes. One example by Warren, Yoder, Gazdag, Kirn, and Jones (1993) described two experiments to study the effects of using a milieu teaching approach to facilitate the acquisition of prelinguistic communication skills. The descriptions of the intervention model and approaches draw on much of the current research and theorizing about early communication, both in typically developing children and in children with developmental delays. The authors noted that the frequency, clarity, and extent of naturally occurring prelinguistic communication have been shown to be at lower levels in children with mental retardation. This might suggest that to rely exclusively on what is known about mother-child interaction with typically developing children to design interventions may not be adequate. Thus, poorer clarity of communicative intent or failure to attend adequately to auditory stimuli on the part of children with developmental delays may make it difficult to create and maintain effective communication situations. To deal with some of these problems, the authors described several principles for facilitating prelinguistic communication based on developmental theory and behavioral principles (i.e., contingent imitation, responsivity, following the child's lead, use of social routines). Indeed, the authors stated that milieu techniques have been shown to be helpful for teaching vocabulary and facilitating pragmatic forms such as requesting and commenting once words have been acquired but that this particular study represents a downward extension of that model to the prelinguistic period preceding initial word acquisition.
The first study involved one 20-month-old boy with Down syndrome; the second study included four 23- to 30-month-old children with developmental delays, one of whom had Down syndrome. Using a multiple baseline design, the training involved the use of interactive play sessions aimed at increasing the children's use of requesting, commenting, and vocal imitation in communicative contexts. The actual treatment program took place in a center-based program and involved the child engaging in interactive play with an adult (two different adults were used with each child to facilitate generalization across people). The data consisted of observations of the child's vocal imitation acts, comments, and requests, recorded preintervention and during the course of the intervention sessions. In the second study with four children, the 25-minute training sessions occurred 4 days per week, with total intervention sessions numbering 37, 43 (for two of the children), and 61. The child with Down syndrome was a 23-month-old boy with expressive and receptive language ages at baseline of 8 and 11 months, respectively, as assessed by the Receptive-Expressive Emergent Language (REEL) Scale (Bzoch & League, 1971), a predominantly parent report measure. The results indicated that this therapy model was effective in increasing such prelinguistic functions as commenting and requesting, as measured by the Communication and Symbolic Behavior Scale (Wetherby & Prizant, 1990), but no follow-up data with the REEL were reported. The authors also reported some interesting results indicating that the improvements in the children generalized to the classroom settings where the children spent the rest of the intervention day. In particular, it was reported that the children's teachers increased their appropriate responsiveness in the classroom. The authors speculated that this may have occurred because the children had improved in the clarity of their intentionality in communicating, thus making it easier for the teachers to respond contingently and appropriately to the children's communications.
Based on the assumption that young children need to attend to and make vocal responses to adults in instructional situations, Drash, Raver, Murrin, and Tudor (1989) conducted a study examining the effects of three different positive reinforcement procedures to produce increases in vocal responses in a group of 15 children with Down syndrome, ages 7 months to 4 years. Results indicated that this group of children showed increases in vocal responses over baseline measurements. Although this kind of operant conditioning model of language training may be losing ground relative to models based on developmental psycholinguistic theory and research, particularly for very young children, many early intervention program classrooms with toddlers and preschoolers use approaches largely based on operant conditioning principles. Future research should be directed toward explicating how such conditioning approaches can appropriately be integrated within the context of the current developmental goals of children's IFSPs.
Hearing Loss Of the medical therapies or interventions with young children with Down syndrome, one that has considerable relevance for early intervention is the use of tympanostomy tubes for secretory otitis media because hearing loss, no matter how intermittent, is expected to interfere further with language acquisition. In a recent study by Selikowitz (1993) in Australia, 24 children ages 6-15 years with Down syndrome and bilateral secretory otitis media, seen consecutively, had tympanostomy tubes inserted; they were compared with a group of 21 children from a general pediatric practice who were developing typically but also had bilateral secretory otitis media. Most children in both groups had mild to moderate hearing losses. Subjects from both groups were randomly assigned to surgeons, but all children had the surgery. Hearing testing was conducted about 5 weeks before the surgery and again 9 weeks postoperatively. Among the children with Down syndrome, 40% of the ears continued to have hearing loss after the tube insertion, whereas in the control group, only 9% of the ears had persisting hearing loss. After surgery, functional hearing losses of greater than 16 decibels in the better ear were found for 8 of 24 (33%) of the children with Down syndrome but only 1 of 21 (5%) of the control children. These results, although conducted with older children, suggest that attention to hearing difficulties in children with Down syndrome is critical, even after tympanostomy tube surgery. Surprisingly, attempts to demonstrate direct relationships between the degree of hearing loss among people with Down syndrome and relative skills in language development have not been successful to date (Marcell & Cohen, 1992).
Alternative Communication One of the promising approaches toward facilitating language and communication development is total communication, the simultaneous use of speech and manual signs. Gibbs and Carswell (1991) reviewed reports of this method of intervention for children with special needs, including a rationale for using it with children with Down syndrome. Briefly, they believe that this approach can be helpful with children with Down syndrome, who often are quite delayed in the acquisition of speech, and they buttress this contention by citing a variety of findings indicating that, compared with other cognitive and pragmatic communicative skills (e.g., turn-taking behaviors), expressive language is more delayed for children with Down syndrome. Furthermore, for many children with Down syndrome who may have better visual processing abilities relative to those for auditory processing, oral-motor difficulties, and intermittent hearing losses, these authors propose that a total communication approach to developing speech may be a useful transitional method of communication.
Although there are a few studies of the use of total communication with children with Down syndrome (cited by Gibbs & Carswell, 1991), compelling evidence has not yet been presented to support its superiority as a method of language instruction for this group. In their case study of a 19-month-old boy with Down syndrome (with a Bayley Mental Scale age of 15 months and a Bayley Motor Scale age of 13 months), Gibbs and Carswell reported that the child showed rather remarkable progress in the acquisition of single words and then of two- and three-word combinations (16 verbal words and 34 signs by age 2 years; over 70 words and 50 signs and some two- and three-word combinations by age 2½ years). The authors noted that this child was considerably more advanced than most children his age with Down syndrome, and the parents were quite involved in the program. They caution that "Total Communication may not be equally effective for all children with Down syndrome" (p. 318).
Another case study about a toddler with Down syndrome (Kouri, 1989) found that 62% of her spoken words were first signed, suggesting that a signing strategy may facilitate the development of speech. Using parent reports of the complete inventory of their children's vocabulary, Hopmann and Nothnagle (1994a) and Miller (1992) reported similar findings of considerable sign language use in the early vocabularies of children with Down syndrome. Miller (1992) noted a "disappearance" of the sign language advantage when the children achieved MAs of about 20 months, similar to the reports of Abrahamsen, Cavallo, and McCluer (1985) and Jago, Jago, and Hart (1984) of a sign advantage in early lexical development. Consensus seems to exist on the merits of a total communication environment for young children with Down syndrome before and during the one-word stage of language development. Interpretation of the findings about more advanced children, however, is more problematic. Studies of the use of signs in contrived circumstances (Romski & Ruder, 1984) and observations about the limited use of signs by older children suggest important potential constraints on the facilitative effects of signing. The developmental issue, however, could be the result of a change in the children's environment because nonsigning adults may have a strong bias to reduce their use of signs and their personal educational program of learning new signs when their children increase their use of oral communication.
An early communication intervention model specifically for infants and toddlers with Down syndrome, with a major emphasis on the use of total communication, has been described bv Kumin, Goodman, and Councill (1991). This program model involves 30-to 60-minute-long therapy sessions with the infant or toddler 1-3 times per week. Also included is parent observation and instruction on how to improve the child's communicative abilities through home activities. The therapy sessions and home activities involve interactive play, individualized to the child's developmental levels of play and attentional behaviors, oral-motor abilities, pragmatic abilities, and receptive and expressive language levels. The explicit focus of the activities appears to be on the development of functional communication. Clearly, the efficacy research about total communication with children who have Down syndrome warrants further well-designed investigation.
Studies to Promote Parent-Child Interactions
In a review chapter about early education for children with Down syndrome, Rynders, Rand, Feuerstein, and Klein (1988) offered arguments for the benefits of early intervention for children with Down syndrome, with the following warning:
Showing statistical differences favoring one type of prograin over another is not the same as showing fully meaningful differences–that is, differences that are culturally relevant and important, lasting, and valuable to the person with Down syndrome, to his parents, and to society in general, (p. 139)
In a general way, they summarized data from eight early intervention studies, but, more important for our purposes, their comments about early intervention suggest that there are a variety of goals and effects of early intervention that have not been fully described or evaluated. For example, early intervention often helps provide social, emotional, and informational support to the family as they begin the initial adaptation to having an infant with a disability. Assisting families to begin to establish enjoyable and stimulating parent-infant interactions, often proposed to be an essential factor for facilitating all future development, is now viewed by many as an appropriate and important goal of early intervention. Improving parents' knowledge about early development and creating situations to promote their confidence in child rearing could also be viewed as measurable early intervention outcomes. To our knowledge, research on these types of parental outcomes with this population has not been conducted to date, nor is there any documentation about how such enhancement of parental knowledge and confidence relates to child developmental outcomes.
Perhaps because of some of the research on parent-infant interactions with infants with developmental delays, including those with Down syndrome, there is an interest in developing and researching intervention programs and techniques aimed at enhancing interactional skills. A number of nonempirical articles can be found focusing on suggestions for promoting mother-child interactions. Many of these suggestions seem to be intuitively reasonable, derived from developmental studies (e.g., Sandall, 1988). In addition, there are a few recent empirically based publications on this topic. One example is a study by Seifer, Clark, and Sameroff (1991) that examined the effects of interaction coaching in a sample of 40 mother-infant dyads with infants with developmental delays. Some of the dyads included a child with Down syndrome. The intervention group (23 dyads) received an 18-month program aimed at improving the mothers' interactional behaviors with the infants. The goal of the treatment was to assist the mothers in becoming more contingently responsive to the infants and to have more reciprocal and enjoyable interactions with them, although this report does not provide further details about the treatment program. The mothers in the control group of 17 comparable dyads watched videotapes of their interactions with their infants with a technician, but no specific training about the interactions was provided. Ratings of videotaped interactions on four dimensions of mother behavior and four dimensions of child behavior were made to measure the effects of the program. The results indicated that there were positive effects of the program for both mothers and infants when compared with the control group dyads. Specifically, the coached mothers showed increased responsivity and less intrusive interactive behaviors, and their infants were less fussy in interactions and showed a significantly greater mean gain in overall MA over the 18-month treatment period (6.3 vs. 4.4 months' gain). It would be informative in future research to include some evaluation of whether such coaching also leads to increases in parents' and infants' enjoyment of their interactions and to analyze and report effects for infants with Down syndrome separately.
In another report based on this same early intervention program, Brinker, Seifer, and Sameroff (1994) described the application of a transactional model to their evaluation of the effects of a 10-month center-based program on child development outcomes and parental stress. Of the sample of 144 families studied, 57 (40%) had infants with Down syndrome, although again analyses were not presented separately for this group. Regression analyses using the entire sample showed complex relationships among the child's initial developmental level, measures of initial parental stress and socioeconomic status, and degree of early intervention participation. For the discussion here, notable findings include the following observations:
This kind of transactional research is important in demonstrating that common notions and assumptions about early intervention effects on parents and family functioning may be too simplistic, erroneous, or both (i.e., greater amount of participation leads to greater developmental gains).
- Children with more significant delays initially showed the slowest developmental progress regardless of maternal stress.
- Degree of early intervention participation (reflected in number of early intervention sessions attended and number of community agencies involved with the family) was not a significant predictor of subsequent child MA.
- For some groups (e.g., initially highly stressed low-income families), more intensive early intervention was related to less improvement in development in the children and increased stress in the mothers.
Treatments to Improve Motor and Physical Development
Several comprehensive reviews about motor development of children with Down syndrome have been published since 1985 (Block, 1991; Henderson, 1985) and are not described further here except to raise several points relevant to early intervention. First, as Block noted, motor development in children with Down syndrome is affected by concomitant anatomical, cardiac, and sensory impairments. Thus, in terms of motor interventions, biological limitations influence some strategies, activities, and goals. Second, significant motor delays are evident very early in the first year of life, and the earliest early intervention programs, as well as current programs, focused on improving overall development, with motor development being one important component (see Chapter 15). Studies of neurodevelopmental treatments and sensorimotor integration therapies, reviewed by Harris (1988), have indicated some benefits, but she concluded that the scientific rigor of these studies has been quite weak. Naganuma (1987) also reviewed studies of early intervention with children with Down syndrome that included study of motor development. She noted that existing studies up to that date had a number of methodological problems that prevented reaching clear conclusions about treatment efficacy. Given the common prevalence of occupational and physical therapy in the IFSPs of infants with Down syndrome, clearly more high-quality efficacy data are needed.
One example of an attempt to evaluate specific motor training for children with Down syndrome was conducted in Sweden by Bjornhage, Lagerwall, Ericsson-Sagsjo, and Waldenstrom (1990). An intervention group consisted of 14 children and a control group of 6 children. The treatment began when the babies were 3 months old and lasted until they began to walk, focusing on increasing muscle tone, reducing incorrect patterns of movement, training typical movement patterns, and stimulating trunk rotation. The treated children performed better than the control children in four areas measured: gross motor, fine motor, kinesthetic perception, and tactile perception (although neither exact measures nor blindness of examiners was described in this report). Interestingly, boys in both groups did better in terms of gross motor and kinesthetic skills, whereas treated girls showed better fine motor and tactile perception skills than untreated girls and both groups of boys. No treatment effects for muscle tone were found. The authors specified that one aim of the study was to try to determine whether earlier acquisition of motor skills might promote mental and social development. Unfortunately, the study report contained no data about this intriguing issue.
An example relevant to this issue is a single case study report that describes the use of neurodeveloprnental techniques with vestibular and tactile techniques to improve motor, reflex, prelinguistic, and cognitive development in an infant with Down syndrome with significant hypotonia and developmental delay (Edwards & Yuen, 1990). An individualized home-based intervention program consisting of weekly 30-minute sessions for a 9½ month period of time was described. The authors reported benefits of the therapy in terms of a slowing of the decline in overall development as assessed by the Bayley Mental Scale, with improvements in oral-motor and reflex development, attention span, interest, and sociability during play, but little developmental progress in either receptive or expressive language.
Another example of research aimed at a specific physical behavior with potentially important interpersonal significance is a study by Purdy, Deitz, and Harris (1987) in which they examined the effects of two treatments for reducing tongue protrusion in a group of five 21- to 31-month-old children with Down syndrome. The authors described a single-subject withdrawal research design with replication consisting of three conditions: baseline, intervention, and return to baseline. Three children received an oral-motor treatment, and two received a behavior modification treatment. Briefly, the oral-motor approach involved manual manipulations of the child's cheeks, tongue, and lips using the adult's hands and using ice. The behavior modification approach used reinforcement techniques to encourage the child to keep the tongue inside of the mouth (i.e., use of praise; withdrawal of toys and attention when tongue was protruding). Parents and therapists carried out the program, and observations of the child's tongue protrusions were made during attendance at school, which were then plotted and visually inspected for treatment effects. Both forms of treatment seemed to be effective in reducing tongue protrusions. For several children there was not a return to baseline when the treatment phase ended, which could indicate either that there is a carryover effect beyond the treatment phase or that typical developmental progression produced the improved tongue posture.
Effects of Inclusion in Integrated Settings
Despite the increasing interest in and advocacy for full inclusion for children with developmental disabilities, few studies exist in which careful evaluations of the effects of inclusion have been undertaken, both for youngsters with developmental disabilities in general and specifically for those with Down syndrome. Casey, Jones, Kugler, and Watkins (1988) reported on the outcomes of a group of 36 children with Down syndrome from London, half of whom attended general nursery or primary schools and half of whom attended segregated special schools. Initially, the children ranged in age from 3 years 8 months to 10 years, and placement in the mainstream versus special schools was determined by policies of the local school districts (and in three cases by parent preference) not by random assignment. In four districts, special school placement was the policy, and in another six participating districts, general placement was the policy. Other characteristics of the districts that would be important to establish comparability were not described. The mainstream group appeared to be slightly younger, with a greater age range, but the two groups were MA matched. A variety of standardized intelligence and academic tests were used (by one nonblinded examiner) to compare the children in the two groups at baseline and again at 6, 12, 18, and 24 months. The results indicated that
The authors discussed the results cautiously because of the small sample size, suggesting that the presence of more able peers may have facilitated language comprehension of the mainstreamed children, but they argued that further study of the effects of general placements is needed.
- At baseline, the two groups were comparable on all measures, but the special schools group was slightly older than the mainstream group, and girls had higher expressive language scores than did boys.
- At the fourth posttest, mainstreamed children had higher scores on measures of numeracy and comprehension only.
- Over the 2-year period, the mainstreamed group had a significantly greater mean MA gain of 19.0 months, compared with 14.2 months for the special schools group.
- The percentage of children reading with any comprehension appeared to improve more for the mainstreamed children, especially the girls.
In the evaluation of the children with Down syndrome from the outreach sites of the University of Washington Model Preschool Program reported by Fewell and Oelwein (1990, 1991), described previously, the authors reported that some of the children were integrated in settings with peers without disabilities but that the amount of time spent in integrated settings (average number of minutes per week) was not a strong predictor of developmental progress.
It is imperative that continuing research addresses questions about the efficacy of interventions within integrated settings and that future studies include more detailed assessment of the features of the integrated settings (e.g., instructional strategies used, characteristics of staff). Our anecdotal clinical experiences indicate that many young children with Down syndrome are now spending time in a variety of community settings with typically developing peers, but the effects on the children with Down syndrome are largely unknown. Well-designed efficacy research on this topic, although limited to date and urgently needed, will be difficult to conduct. In a review of the effects of integrated versus segregated settings on young children with disabilities, Buysse and Bailey (1993) concluded that inclusion in integrated settings may be "beneficial socially for some pre-schoolers with disabilities" (p. 457). Their review indicates, however, that little is known about children with Down syndrome per se, largely because few studies specifically address this population or, when children with Down syndrome are included, analyses are not presented separately for them.
A major strength of the Buysse and Bailey (1993) review is the authors' detailed delineation and review of current knowledge of 13 programmatic variables identified by Guralnick (1981) as critical for an understanding of inclusion settings (e.g., ratio of children with disabilities to children without disabilities; level of teacher training; chronological age and severity of disability; developmental model of program). For each of these variables, considerable additional research is needed (e.g., few studies have included children with severe disabilities; no studies have involved children less than 2 years of age).
It is also critical that a variety of child outcome measures be included in future studies of the effects of inclusion, including social competence, self-esteem, and language use, to name a few. Such studies must be longitudinal by design in order to capture the process of developmental change as it may occur in these settings, with the expectation that change will occur slowly.
AN ETHOLOGICALLY BASED DEVELOPMENTAL PERSPECTIVE
An evolutionary perspective (Scarr, 1992) may offer a useful way of integrating some otherwise disparate observations, shed light on connections between development for infants with disabilities and those who are developing typically, and provide a set of assumptions for future research investigations. Within this framework, infancy stands out as a period of development during which both the child's behavior and the caregiver's behavior with the child are highly canalized (i.e., genetic preadaptation [that there are relatively similar phenotypes across wide variations in environmental circumstances] ). Papousek and Papousek (1987) distinguished among different types of caregiving behaviors, with "Intuitive Parenting" occupying an intermediate position between innate reflexes and caregiving that is related to rational decisions. The interactions that characterize so much of "playing with baby," when both baby and caregiver engage in complex, carefully timed interpersonal interactions, may stand as the exemplar case of Intuitive Parenting, when caregivers are typically unaware of many aspects of their babies' behavior, their own behavior, or the mechanisms that regulate the nature of their interactions with their infant. When either of the partners' behavioral repertoires lies substantially outside the range from which the behaviors evolved, the finely calibrated system is challenged.
Babies with Down syndrome may present this kind of challenge, with innumerable differences in the emergence, timing, and intensity of infant behaviors primarily occurring without caregivers' explicit awareness. For example. Lynch et al. (1995) have shown that infants with Down syndrome both begin canonical (word-like) babbling on average 2 months later than typically developing infants and show less stability in the proportions of canonical syllables in vocal samples after the onset. Lynch and his colleagues suggested that infants with Down syndrome may present deficient signals to their caregivers to modulate their child-directed language and related behaviors. An ethological perspective to development assumes that those aspects of development are particularly at risk with the combination of children who are developing atypically and relevant care-giving behaviors that are relatively unavailable for explicit examination. The importance of this combination may be seen in the common pattern of depressed language competence associated with Down syndrome and, within the general set of communication skills, the relative strength among children with Down syndrome in pragmatics relative to syntax (Hopmann, 1986).
Infants and young children with Down syndrome are being cared for and educated in a highly diverse set of circumstances, frequently without reference to information based on carefully conducted empirical research. Clinical research must be conducted in ways that provide useful guidance for professionals and parents, responding to changing issues, such as the needs of non-English-speaking families. Professionals must create ways of evaluating scientific contributions that arise from diverse circumstances in the field and of disseminating valuable information. This issue has profound implications for training and qualifications of early intervention personnel.
Although individual differences among people with Down syndrome have been documented for some time, little attention has been directed to this critical theoretical and practical issue. Most salient for many continue to be the variations in degree of mental retardation (i.e., impairments in information processing and cognitive processing, including language impairment, resulting in impaired or less than optimal problem-solving abilities, judgment, and thinking skills-in short, cognitive limitations). Conversely, parents and family members seem to benefit to some extent from socialization experiences based on the shared diagnosis of trisomy 21. Rapidly evolving new opportunities can be disseminated in informal parent groups, and a sense of solidarity can help strengthen families during times of stress. Parents who enjoy these shared experiences, however, may cringe when phrases such as "those children" are used to refer to a homogeneous group of all young people with Down syndrome.
Development is slower for children with Down syndrome, making an attempt to implement an intervention and collect outcome data a very lengthy process when outcomes include emergence of specific developmental skills (e.g., producing multiword sentences). Furthermore, with the mandated parent participation and the often persistent strong opinions of parents about which service options they want for their child and family, it will be difficult to conduct clinical research about treatment efficacy using traditional scientifically rigorous designs and methods. Nevertheless, it is imperative that researchers and clinicians educate and engage parents in research about early intervention techniques and programs. Researchers must do a better job explaining that the research enterprise involves an inherent tension. Specifically, those who are implementing an intervention will necessarily and reasonably have a belief and faith in its beneficial effects, whereas those who engage in the scientific study of an intervention must maintain a somewhat skeptical demeanor as they carefully scrutinize the nature of an approach and its effects. It is also important that we avoid overselling the benefits of particular techniques or programs when objective efficacy data simply do not exist. In addition, strategies and interventions based on basic developmental research with infants with Down syndrome (or typically developing infants) are not as straightforward as they might seem initially. For example, how does one intervene to enhance reciprocal contingency in parent-infant interactions when an infant rarely initiates?
Interventions directed at the more complex issues challenging individuals with Down syndrome, such as their language skills, require the participation of caregivers throughout the child's life. Unlike a pill that can be administered to a baby quickly and by any of a set of different caregivers, the communicative interactions between an adult and a young child with a disability may need to be continuous throughout the child's day and carefully guided and monitored. The importance of continuity in the caregiving environment, recognized as critically important for young children as reflected in debates about child care, may be an even more vital characteristic for the caregiving of infants with Down syndrome (and likely other children with disabilities).
FUTURE CHALLENGES FOR SECOND-GENERATION EARLY INTERVENTION
This review of early intervention studies with children with Down syndrome indicates progress in the types of questions being considered and suggests directions for future research. Studies of specific program models, particularly in terms of language and parent-infant interaction models and goals, have begun to produce some evidence of benefits, but further study is clearly warranted. Future studies of how prelinguistic communication is being addressed in early intervention programs are sorely needed, with analyses for children with Down syndrome conducted separately and with attention to the individual variations so apparent in early language acquisition. Such research must be a top priority given the impairments and central role of language and communication skills for people with Down syndrome.
More differentiated questions considering family characteristics and child factors (e.g., hypotonia, cardiac problems), as well as measures of program intensity and parent involvement, have been few and deserve more attention in research designs. Outcomes such as recommended practices associated with providing positive family support have been considered only since the 1990s and loom large as families begin the lifelong task of nurturing and supporting their child's development. A study, such as the one by Shonkoff et al. (1992), that expands the design such that treatment efficacy is the main question is required. Comparisons of treatment models that are well defined and monitored for variations in implementation, and include random assignment and masked assessments, are possible (and indeed necessary) in such a study (Spiker, Kraemer, Scott, & Gross, 1991). Furthermore, researchers have a responsibility to accurately represent the current state of knowledge about early intervention efficacy so that it will be apparent that such studies are needed and deserve funding. These studies must be implemented rigorously and be supported by early intervention practitioners and families. This goal could be better achieved when there is greater collaboration among scientists at sites across the country. It will be unfortunate if the new federal mandate to provide early intervention services carries with it a trend of a reduced role for research about early intervention efficacy because legislators, the public at large, and funding agencies erroneously believe that strong, unambiguous benefits of early intervention have been proven. Many second-generation questions about the context of early intervention remain (e.g., inclusion, types of curricula, nature and extent of parent involvement, aptitude-treatment interaction effects).
Another challenge in the years to come concerns the tension between explicit, self-conscious (not ''commonsense") caregiver behaviors, contingent on specified child behaviors, and the desire to have youngsters with Down syndrome grow like flowers in the field amid all the other children. Interventions such as that described by Dodd et al. (1994) to improve articulation are time intensive for both professionals and caregivers. In addition to the 36 hours of training, the parents attempted to implement the guidelines during each interaction with their child. It is not clear how a neighborhood child care provider could be trained and inspired to provide this type of intervention. Questions about program intensity and specialized training for particular interventions and questions about the goals and realities of implementation of inclusion models must be considered simultaneously in future research. This review indicates that studies of inclusion models with children with Down syndrome are seriously limited, a significant gap given the increasing advocacy for such models.
The increased use of paraprofessionals within the field of early intervention as well as the trend toward inclusion may put increased demands on more highly trained professionals to communicate their goals and techniques carefully to these less well-trained interventionists. This may result in more rigorous descriptions of the actual intervention process, in both the direct work with the child and the techniques to teach and test caregivers' skills. Alternatively, however, we fear that the importance of staff training and qualifications may not be given due attention as changes associated with inclusion models continue to develop and a range of people become part of the early intervention enterprise. Thus, the future research on inclusion must provide detailed documentation about the qualifications, training, and support associated with various models.
Finally, more studies are needed of the effects of early intervention services on parents and families (e.g., Marfo, 1990; Spiker, 1990). As early intervention activities become more integrated into community experiences and a more ecological model evolves, new techniques will be required to document and assess a family's engagement in early intervention as important outcomes. Furthermore, the basic research on parent-infant interactions with infants with Down syndrome and the few intervention studies with parent-child interaction as an explicit focus reported here offer promising directions for future research. The federal mandate in the Education of the Handicapped Act Amendments of 1986 (PL 99-457) and the Individuals with Disabilities Education Act Amendments of 1991 (PL 102-119), aimed at empowering parents regarding their participation in all aspects of the early intervention enterprise- the new parent-professional partnership model-presents significant challenges. Among them is the need to better educate parents about the current knowledge base about early childhood, about development, about Down syndrome, and about intervention strategies, with all the ambiguities and unanswered questions (Able-Boone, Sandall, Loughry, & Frederick, 1990; Ziegler, 1989). Only when parents have this knowledge will they genuinely be empowered and able to participate fully as partners.
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