Stability of individual differences in infants' manipulation and exploration of objects

The purpose of this study was to assess stability of manipulative behavior across time. 29 infants were seen at both 9 and 9.5 mo.; 20 of these infants were seen again at 12 mo. At each visit the infants were presented several objects for familiarization and tested for response to discrepant objects. Each trial was scored for the duration of looking, rotating the object, fingering, mouthing, and banging, the frequency of transferring the object from hand to hand, and the frequency of dropping, throwing and pushing the object away. Analysis of the data yielded moderate to high correlations between 9 and 9.5 mo. for all but one behavior. Correlations between 9 and 12 mo. were in the same range for most of the behaviors. On the test trials, there were fewer significant correlations. When the behaviors were separated into exploratory and nonexploratory categories, there was more stability for the nonexploratory behaviors; summary scores for both were concurrently related to Bayley Mental Development Index at 12 mo., but in opposite directions. The results suggest that there is stability in some manipulative behaviors, and further, that it is useful to conceptualize two types of manipulative behavior.