The relation of length of institutionalization to the intellectual functioning of the profoundly retarded.

The effect of institutionalization was measured in relation to performance on the Cattell Infant Intelligence Scale by 103 profoundly retarded residents with a mean CA of 20.3 years, a mean MA of 18.1 months, a mean IQ of 12.7, and a mean number of years in the institution of 10.6. After partialing out CA and MA, years in the institution was negatively correlated with success in visually directed object manipulation (Cattell items below an MA of 9 months), social imitation (9-12 months), and purposeful, constructive activities (over 20 months). The findings were compared with previous studies on retarded and nonretarded infants and children.