Use of the Bayley Scales to characterize abilities of premature infants.

The Bayley Scales of Infant Development were administered to 92 white, middle-class infants, half of them premature and half full-term, at 1 year of age from term to determine whether this instrument is useful in characterizing the abilities of premature infants. Although both full-term and premature infants achieved mental and motor development scores within the average range, full-term infants attained significantly higher scores on both the Mental and Motor Scales. Both groups scored significantly lower on motor than mental functioning; however, the difference was significantly greater for premature infants. As a group, premature infants also evidenced greater variability in their performance on both the Mental and Motor Scales, and they showed greater intra-individual variability in performance of motor ability. Furthermore, premature infants were less likely to succeed on items testing eye-hand coordination, imitation, and vocalization. Preselected perinatal risk variables accounted for a significant amount of variance in both mental and motor ability of premature infants.