Cognitive Processes in the Child with Down Syndrome

Santiago Molina and Ana Arraiz Perez Developmental Disabilities Bulletin 21(2) 1993 University of Zaragoza, Spain

Reprinted with the permission of Dick Sobsey, Director JP Das Developmental Disabilities Centre University of Alberta 6-123 Education North Edmonton, Alberta T6G 2G5 Canada

Cognitive processes of children with Down Syndrome (DS) and others without DS but with mental retardation (MR) were assessed first in a standard static form, followed by a session of mediated learning and reassessment. The cognitive processes that were assessed comprised planning, simultaneous and successive processing. The subjects were 30 typically developing children 5-7 years of age, 60 children with MR and 30 children with DS between 9 and 12 years of age. The groups were comparable on the Columbia Mental Maturity Scale. The children with DS were particularly poor in successive processing and planning. The dynamic assessment involving mediated learning improved the DS children's successive processing more than planning or simultaneous processing. This implies a greater learning potential for successive processing, even though children with DS are known to be deficient in this type of processing; a very brief mediated learning session could ameliorate their deficiency.

Few studies have aimed specifically at analyzing information processing and learning abilities of individuals with Down Syndrome. This may be due to the traditionally heavy reliance on general IQ measures and the lack of appropriate tests on specific cognitive functions. More recent studies that have used Das, Kirby, and Jarman's (1979) model of information processing have found differences between individuals with Down Syndrome and other individuals with mental handicaps. Snart, O'Grady, and Das (1982) showed that children with Down Syndrome scored significantly poorer on some of the successive processing tasks than the other groups with mental handicaps in their study. Similarly, Pueschel (1985) found that persons with Down Syndrome scored poorer on successive processing and planning tasks than individuals with average abilities. Lincoln, Courchesme, Kilman, and Galambos (1985) explain this deficiency by attributing it to a neurological problem. Other studies that have shown auditory memory deficits in children with Down Syndrome will be mentioned later.

The study presented in this article is part of a larger research project aiming at assessing information processing in children with mental handicaps. The present study concentrates on two different groups; a) children with Down Syndrome (DS), and; b) children with mental retardation (MR) with no known genetic etiology or organic brain damage. The study is theoretically based on two approaches: Vygotsky's (1985) notion of the zone of proximal development, and Das, Kirby, and Jarman's (1979) model of the three basic cognitive processes: simultaneous coding, successive coding, and planning. The main focus of the study is to investigate the information processing of children with Down Syndrome. We will also compare the learning abilities of the DS group with individuals with mental handicaps whose retardation is without genetic etiology by employing mediation or a cognitive training program between the pre- and posttests. One of the main underlying questions of the study is whether there are any scientific foundations to argue that individuals with Down Syndrome should be classified separately from individuals who are classified as mentally handicapped.

In order to answer these questions, the application of cognitive training programs was required. Before the three cognitive processes could be analyzed, the programs had to be adapted to suit the precise characteristics which the individuals with handicaps demonstrated. The specific questions and hypotheses that we wanted to address are as follows:

1. Do children with DS demonstrate the same level of ability in solving simultaneous, successive, and planning tasks as other children with MR who are of the same chronological age and mental maturity level? We assume that the group with DS will perform poorly compared to the group with MR in successive processing tasks and in all auditory tasks, whereas when simultaneous, planning and visuo-motor processes are involved, the group with DS will perform equally or better than the group with MR.
2. Are there any differences in learning potential between the two groups that receive remediation, and do both groups benefit from remediation? We assume that the differences between the groups in learning potential will be reduced when mediated learning occurs between pre- and posttesting.
3. What learning potential does the group with DS display in the three cognitive processes assessed? We assume that the learning potential of children with DS will be different for each of the three cognitive processes; it will be the best in simultaneous and planning processing, and the worst in successive processing.

Method

Subjects

Three groups of subjects with a similar mental maturity level were used. The first group comprised 30 children without handicaps whose chronological ages ranged from 5 to 7. The children's mental maturity level (M = 74.00; SD = 12.00) ranged from 60 to 96 (Columbia Mental Maturity Scale).

The second group (MR) comprised 60 children with mental retardation with no known brain damage or genetic etiology. The group with MR was divided further into control and experimental (remediation) groups which consisted of 30 randomly-matched subjects in each group. The mental maturity level of the experimental group with MR ranged from 60 to 109 (M = 72.37; SD = 12.14; Columbia Mental Maturity Scale), and the mental maturity level of the control group ranged from 41 to 109. Chronological ages of individuals with MR ranged from 9 to 12.

The third group (DS) comprised 30 children with Down Syndrome. The group with DS was also divided into control and experimental groups. Both groups consisted of 15 randomly-matched subjects. The mental maturity levels of the two DS groups ranged from 51-108 (M = 78.87; SD = 18.56) in the experimental group, and from 48 to 109 (M = 80.67; SD = 20.39) in the control group. Chronological ages ranged from 9 to 12.

Tasks

Cognitive processing of the subjects was assessed by the Dynamic Assessment of Learning Potential and Cognitive Strategies Battery (Molina, Arraiz, & Garrido, 1992). This battery consists of nine tests which represent three cognitive processes as described below.

Simultaneous processing

Reversible Thinking (RT). This test is constructed to measure conservation of quantity, number, and hierarchical class inclusion as discussed in Piaget's theory. The test is suitable for children who are in the beginning of the concrete operational stage. The test consists of cards with drawings and three dimensional blocks. In the first items, the subjects were required to both manipulate the stimulus material and give a verbal answer; in the last items, only verbal answers were required. For determining learning potential, mediators were also used. These included key instructions and modeling. Slightly different objects or variations in the positions of these objects were used in the pre- and posttest.

Matrix Designs (MD). This test is an adaptation of Raven's and Budoff's test. Two types of mediators were used as well, which were either spatial or verbal. Parallel designs were used in pre- and posttest

Successive processing

Digit Recall (DR). This test is similar to the WISC-R Digit Span task. Both forward (3-5 digits) and backward (2-4 digits) forms were used. The mediators were verbal repetitions of the digits by the examiner or visual presentation of the digits on cards.

Visual Short-term Memory (VSM). In this test, the subject is shown a sequence of drawings of objects belonging to the same category with one distracter among them. The subject is then asked to identify the distracter seen on a subsequently presented card. A verbal distracter rather than a pictorial form is used in the second part of the task. Two kinds of mediators were used; the visual mediators were objects belonging to the same category as the target objects, the verbal mediators were the name of the category to which the target objects belonged. In the maximum prompting condition, the items were repeated by the examiner. For the posttest condition, the items and the category were changed.

Serial Ordering of Pictures (SP). This task consists of placing a series of picture cards presenting a story into a logical order. The first or the last card of the series was shown for prompting, thus acting as mediators for this task.

Verbal Ordering of Stories (VS). This task is similar to the previous one, the only difference being that now the sequencing must be done verbally rather than by manipulating the cards; the mediators were also similar to the previous test.

Planning

Spatial Structuring Designs (SSD). This test is based on the WISC-R Block Design test. Some designs were simplified in order to adapt them for the performance level of our subjects. As mediators we presented the designs in their actual size and gave prompts regarding the solution of the design. In the posttest condition, the color of the blocks was changed.

Mazes (M). This task is an adaptation of the WISC-R subtest of the same name. The mediators consisted of indicating to the subjects some typical sources of error, either verbally or visually, and encouraging them to re-examine the mazes. The posttest was similar to the pretest, with the exception that the arrangement of the mazes was changed.

Puzzles (P). This task is based on the Object Assembly subtest of WISC-R. The mediators consisted of showing the subject the concept which every puzzle represented either verbally or visually. The posttest consisted of designs similar to the pretest in number of pieces and in familiarity.

Procedure

The control groups with DS and MR were given pre- and posttests. The pretesting session was similar to the way in which psychometric tests are given. The posttests were variations of pretests and similar to them in difficulty level.

In addition to pre- and posttests, the experimental groups received mediation. The mediators were cues and prompts for solving the task that were presented to the child if the child had answered incorrectly in some parts of the pretest. Children without mental handicaps only received the pre- and posttest and were therefore used as another control group. The aim of the posttest obviously was to verify the effect of the mediating condition for the experimental groups.

Results and Discussion

Cognitive Processes

To compare the differences between different groups in cognitive processing, three processing scores, one each for simultaneous and successive processing and planning, were first calculated for each group by summing the raw scores from respective tests. T-values (Student's t test) of differences between different groups both in pre- and posttest are displayed in Table 1.

As Table 1 shows, children with Down Syndrome performed at a significantly lower level than the group with MR in all of the three cognitive processes. There were only two exemptions, both in line with our predictions. In posttest control condition, there was no significant difference between the groups with DS and MR in the simultaneous processing score, and in posttest experimental condition there was no significant difference between the groups with DS and MR in the planning score.

It is also interesting to note that when the children with Down Syndrome were compared to children with mental handicaps of a similar level of mental maturity, significant differences existed in all three cognitive processes even when the group with DS received mediation in the posttest condition (see column 4 in Table 1). Table 2 presents the same differences for each subtest on the battery in the posttest condition.

Simultaneous Processing

According to Table 1, the group with DS performed the tasks of assessing simultaneous processing at a lower level than the group with MR in the pretest condition. Snart et al. (1982) also found lower performance levels for children with DS in simultaneous processing, but in their study the differences were not statistically significant. In our study, simultaneous processing was measured by two tasks: Reversible Thinking and Matrix Designs. Table 2 shows that in Matrix Design, the groups with DS and MR were not significantly different in any of the four comparisons. In the Reversible Thinking task, however, the experimental group with DS obtained significantly lower scores both in pre- and posttest than the experimental group with MR.

The partly contradicting results may be explained by the fact that Reversible Thinking demands concrete operational thinking from the subjects, and part of the group with DS may not have reached this developmental stage. The size of the group with DS was small (15 subjects in both conditions) and both their mental and chronological ages varied considerably, making it more likely that some of the children had not reached the concrete operational stage. This hypothesis is endorsed by Lister, Leach, and O'Neill (1989), whose study related the large differences found between children with Down Syndrome and other children with or without mental handicaps to specific difficulties in number acquisition for the children with DS. Thus, we believe that differences in Reversible Thinking must be interpreted in Piagetian terms as differences in cognitive development rather than differences in simultaneous processing. The fact that the differences in pretest and posttest conditions are similar supports this hypothesis further.

When children with DS are compared to children without mental handicaps, the differences in simultaneous processing are clear. The performance level of the group with DS is significantly lower in both tests, and these differences existed even when the group with DS received mediation before the posttest. These results coincide with those of Pueschel (1985) and suggest that children with Down Syndrome are deficient to children without mental handicaps of similar mental maturity level in simultaneous processing.

Successive Processing

The most conclusive finding of this study is that the memory processes of children with DS are deficient compared to the other two groups. If we take into account the importance of short-term memory in successive processing tasks, it is understandable that the group with DS performed significantly poorer than the other two groups in all of them.

Poor performance of children with DS in auditory Digit Recall task (DR) has been verified also by other researchers (e.g., Snart et al. 1982; Varnhagen, Das, & Varnhagen, 1987; Walti, Salvisberg, & auf der Maur, 1973). Our results also suggest that the auditory-verbal modality (DR) is weaker than the visuo-motor modality (VM) in the group with DS. In the Visual Short-term Memory task, the differences between the group with DS and the group with MR disappeared once the strategy of chunking was given to both groups (experimental posttest condition). This result confirms the strategic deficit of children with DS found by Herriot and Cox (1971) in the visual inspection tasks. The fact that the significant differences persisted in tasks in which the auditory component was more prominent, seemed to confirm the conclusion by Lincoln et al. (1985) that children with DS have more disturbances in auditory-verbal processing. This can also explain the lower performance levels of the DS group in Verbal Ordering of Stories. Also, the lower performance level of the DS group in Serial Ordering of Pictures may be a result of the test's implicit semantic content. Silverstein, Legutki, Friedman, and Takayama (1982) have shown that children with DS have considerable difficulties in solving these types of tasks.

Our results confirm, once again, that the visuo-motor abilities of children with DS are superior to their verbal abilities. The deficiency of verbal processing in individuals with Down Syndrome is also evident when they are compared to children without mental handicaps. Furthermore, McDade and Adler (1980), Marcell and Armstrong (1982), and Stratford and Alban (1982) have all shown that auditory recall and visual inspection, both being successive tasks, are equally deficient in individuals with Down Syndrome, regardless of the use of mediation.

Planning

A similar phenomenon was found with planning as with simultaneous processes. When children with DS were compared with the MR group, the results were rather contradictory. The DS control group performed significantly poorer than the MR control group in all six comparisons, whereas the experimental groups with DS and MR did not differ from each other in any of these comparisons.

These contradicting results can be attributed to the wide range of mental maturity levels and chronological ages in DS and MR samples. Also, some of the subjects may have rehearsed two of the planning tasks (Spatial Structuring Designs and Puzzles) at school. Glasser and Zimmerman (1980) demonstrated that previous practice has an important effect on performance in this test

When compared to children without mental handicaps of the same mental maturity level, the planning processes of children with Down Syndrome are clearly poorer. The differences are least in the Puzzles task when completed by the experimental group of children with DS (Table 2). This finding can be explained by the characteristics of this task (visual-motor, non-semantic and non-abstract content). Also, the difference between children without mental handicaps and the experimental group with DS decreased in the Spatial Structuring Designs from pretest to posttest (see Table 2), indicating that the group with DS benefited from the mediation. That children with DS show learning abilities in this type of task could be explained by the fact that these tasks engage the visual-motor functions and have a figurative content. These hypotheses have been supported by Belmont (1971), Gibson (1978), and Pueschel (1985).

Because of the ambiguity of our results, we feel that it is necessary to conduct a more clearly defined study of the planning processes of children with DS and MR. Little research is done on the planning processes of these individuals. We therefore recommend that these results be interpreted with some caution.

Learning Potential

The learning potential of children with DS was evaluated by calculating the difference between experimental and control groups in the posttest scores. If these differences are significant, we can assume that mediation has helped the experimental group to perform better in the task, i.e., they have potential to learn and benefit from mediation. Also here, Student's f test was used to assess the significance of these differences. The results of these analyses are presented in Table 3.

The last row in Table 3 shows that children with DS were able to benefit from mediated learning. This is an important result since these children initially performed at a lower level than the group with MR in most of the tasks, as can be seen in Table 2. We believe that some of the originally deficient performance may be due to specific learning problems that children with DS manifest. This assumption is supported by Wishart (1991), who showed that young children had a problem of learning consolidation. Wishart's study showed low performance levels in previously learned tasks, and, paradoxically, rapid learning in tasks which can be interpreted as relearning tasks.

In planning tasks, a significant improvement is shown both in Mazes and in Spatial Structuring Designs tasks. This implies that the subjects clearly showed potential for learning at least some kind of planning processes, although it is important to remember the possible effects of previous experience in these types of tasks.

Table 3 suggests that the subject's learning potential was lowest in simultaneous processing; no significant improvement is demonstrated in either of the simultaneous processing tasks. As discussed above, the lack of improvement in the Reversible Thinking task may be due to the possibility that a considerable part of our sample had not yet arrived at an adequate level of development to benefit from the mediation. The experimental group's insignificant improvement in the Matrix Design Test can be due, in part, to the possibility that each task in the posttest becomes a cue, thus invalidating the differences between the experimental and control conditions. For example, Schrotz (1975), who used a task in which the subjects had to complete geometric designs, found that the performance of children with DS improved after several trials and arrived at the same level as that of the children without mental handicaps, and control groups with MR.

Finally, it is surprising that children with DS demonstrated considerable learning potential in successive processing, especially if we remember that their main deficit is in this mode of processing. However, keeping the problem of learning consolidation in mind, our results can be explained by suggesting that the underlying capacity for successive processing in children with DS is greater than their apparent performance. In other words, many of the successive processing tasks could have been poorly learned, thus creating the necessity for a small cue to be given in order for learning to occur.

We should also notice, that the only successive processing task in which there was no improvement was Digit Recall, an auditory-serial memory task. This result supports the earlier conclusion that processing auditorially presented successive tasks are most difficult for individuals with Down Syndrome.

Conclusions

This modest study shows that children with Down Syndrome have a lower effective rate of development than other children with mental retardation of the same chronological age and mental maturity level. This is especially true for successive processing and planning, and less so for simultaneous processing. The differences in simultaneous processing may be principally produced during the acquisition of number concepts.

Furthermore, it is necessary to notice that the modality of the task plays a significant role for children with DS. These individuals did clearly better in visuo-motor tasks than in tasks with auditory-verbal content

When children with DS and children without mental handicaps of the same mental maturity level are compared, the poor performance of the former is apparent in all three cognitive processes. Furthermore, these differences persisted even when children with DS received mediation. These results suggest that, although children with DS can benefit from mediation, their cognitive processing skills remain poor to those of children without mental handicaps even when the two groups are matched on the basis of their level of mental maturity.

The learning potential of children with DS was different in the three cognitive processes which were analyzed in the present study. It is surprising that improvements in successive processing are greater than improvements in simultaneous processing. In our opinion, these results show important specific features related to information processing of children with DS as well as their capacity to learn. The results must, however, be interpreted with caution as there is very little research in this field.

References

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This paper by Garcia and Perez is part of a larger research project in which two approaches have been combined — the neurocognitive approach of Das and colleagues, viewing intelligence as comprising specific cognitive processes, and the mediated learning procedure of Feuerstein¹. This study has an optimistic outcome in that children with Down Syndrome show significant potential for learning a cognitive processing skill; this is the skill in which they are characteristically deficient. The authors did not have access to the battery of tests for measuring the cognitive processes operationalized by me and my colleagues; hence they have selected their own battery. Whether or not their tests can be good substitutes for those used by us remains to be proven.

This paper has gone through several revisions for clarifying the expressions and rendering it in acceptable English; we still do not think that we have done a good job. Much of the credit for editorial revisions must go to Rauno Parrila, a doctoral student in Educational Psychology at the University of Alberta.