The affective response of Down's syndrome infants to a repeated event

In a study with 17 Down's syndrome infants, the older infants (mean age = 20 months, 6 days) responded to the regular reappearance of a squeaky doll with significantly more affective behavior than did younger infants (mean age = 9 months, 24 days). When the 10 younger infants were included in a longitudinal study of their responses to this same event, the onset of affective behavior was significantly correlated with the mental development index of the Bayley Scales of Infant Development, and was also associated with some aspects of temperament as measured by the Carey Survey of Temperamental Characteristics: these aspects were poor adaptability to change and a low tendency to approach new situations.