Three measures of verbal input organization (category clustering, associative clustering, and subjective organization) were employed to compare the performances of 30 normal and 30 educable mentally retarded (EMR) elementary school males of equal chronological age on various free recall learning tasks. Subjects were given 12 successive trials on each of five stimulus lists. Findings indicated that EMR children demonstrated less category clustering and recall than normal boys on the categorized list, and less associative clustering and recall than normal boys on a stimulus list composed of high associative paradigmatic noun pairs. EMR subjects demonstrated significantly less recall than normal boys on stimulus lists composed of either low associative paradigmatic or low associative syntagmatic word pairs. Investigators focused on M. Semmel's model of the language behavior of EMR children as a guide. Reviewed was the literature on the major psychological theories attempting to explain the organizational processes involved in learning and memory, on category clustering in free recall, on associative clustering in free recall, on subjective organization in free recall, and on clustering studies of children. (Author/GW)