Mirroring this cognitive decline, social and adaptive skill development also decelerates with age in DS children. Early intervention programs for DS children focus on prevention of skill deterioration.
DS children participating in such programs increase or maintain IQ scores and developmental quotients from infancy to school age the period in which the greatest decline in scores is normally seen. DS children demonstrate poorer verbal skills on tests of psycholinguistic ability than do other moderately retarded children.
Auditory-sequential abilities are also weak. DS children perform well on tasks requiring manual expression and visual reception. Children in other etiological categories showed minimal, if any, discrepancies between auditory or visual language skills. DS children also demonstrate limitations in other perceptual abilities. Infants as young as 8 months have shown deficits in visual attention, tactile and auditory perception, and auditory-vocal integration. Motoric skills in DS children do not appear deficient as compared to non-DS retardedindividuals, since measures of simple visual-motor reaction time are similar in these groups.
To summarize, the DS child shows a gradual decline in cognitive abilities from infancy to early childhood, after which abilities seer to level off until adulthood. Early intervention programs tend to offset developmental delays for these children, whereas institutionalization tends to accentuate them. DS children generally perform poorer than non-DS retarded children on tasks requiring verbal and auditory skills. In contrast, performance on tasks which capitalize on visual and motor skills do not appear deficient in DS children.
The extent to which auditory perceptual weakness can be augmented by coordination with visual strengths is yet undetermined in the DS population. There is a great deal of cognitive and perceptual variability in DS children and adults. Intelligence ranges from mild to profound retardation. There is considerable heterogeneity in rates of cognitive and personality development among DS individuals. One must therefore use extreme care in deciding whether to attribute research findings to the DS population as a whole, or conversely, to interpret those findings as characteristic of specific cognitive or developmental levels.
