Contingency learning in 9-month-old infants with Down syndrome.

The ability of ten 9-month-old infants with Down syndrome to acquire a contingency in which arm movements were reinforced with auditory and visual stimulation was assessed. Unlike a group of infants without identifiable disabilities, those with Down syndrome did not learn the contingency. Examination of the performance of individual infants with Down syndrome indicated that some infants did master the contingency. In addition, there was a relation between contingency performance and scores on the Mental Development Index of the Bayley Scales of Infant Development. Results were discussed in terms of the possibility that some infants with Down syndrome experience a decline in conditionability with age and the relation between conditionability and mental development.