A comparison of two developmental instruments in evaluating children with Down's syndrome.

Twenty-one children with Down's syndrome were given both the Bayley Scales of Infant Development and the Gesell Developmental Schedules. Mental and motor developmental lags measured on the Bayley Scale were found to be significantly larger than comparable lags measured on the Gesell Schedules. Further, developmental lags for the mental and motor portions of the Bayley were not significantly different. For the Gesell, however, mental lag was significantly larger than motor lag. Finally, mental and motor lags increased with chronologic age on the Bayley, but only mental lag increased with age on the Gesell. These discrepancies indicate that for this population of infants the Bayley and the Gesell are not interchangeable assessments because they do not yield the same developmental patterns.