The measurability of sensorimotor development in 60 severely retarded, institutionalized adults was studied, using the Piagetian concept of object permanence in a delayed recall paradigm that involved special apparatus. Results suggested, among other things, that severely retarded, institutionalized adults learn most efficiently when trained with no interpolated delays. Modest correlations were found between performance on the object permanence tasks and on the Bayley Motor Scale, and somewhat stronger correlations were found between object permanence task performance and Bayley Mental Scale scores. The Vineland Social Maturity Scale scores tended to correlate in an intermediate range between the two Bayley scale scores. The Ss were shown to be capable of representational schema and of retaining memory of an image in relation to external cues over brief time periods of a 30 second delay. Their level of development of representational schemata functioning appeared to be similar to that of 36 month old normal children. (Author/DLS)