H. Corman and S. Escalona's scales for object permanence and spatial relationships were readministered to 71 severely and profoundly mentally retarded individuals (mean age 19 years) five years after the last previous administration of the scales. Gains in mean scores were small but statistically significant for both scales. (Author)

Scales for object permanence and spatial relationships were administered to 98 severely and profoundly mentally retarded children (mean age 13 years) on three occasions, 6 months apart. Differences in the difficulty of the items were quite stable, but their order of difficulty differed appreciably from that for nonretarded infants. (Author/SB)