Sixteen white home-reared babies (eight boys - eight girls) ranging in age from six months to two years were studied during home visits. Piaget's sensory-motor development theory of imitation was employed, and his special thesis of the hierarchical sequence was tested. The examiner proposed four critieria for assessing the development of imitation during this period: (1) accuracy of the imitation, (2) speed at which imitations are acquired, (3) complexity of imitation infant is capable of acquiring, and (4) novelty of the imitation. Findings conformed to the Guttman quasi-simplex correlation matrix, and demonstrated existence of a developmental sequence. The examiner proposes further investigations relating imitation during the sensory-motor period to application of measures of affective development. (Author)