Mentally retarded children's abilities in the process of comparison.

Mentally retarded children were asked to make various types of comparisons between sets and subsets of objects. Results showed that they succeeded when the comparison involved numerically unequal subsets of objects within the same set. When sets, or subsets, were numerically equal, the children clearly failed; instead of rejecting both alternatives in the comparison question, they selected one. With other comparisons, within and between sets and subsets of objects, the children guessed at an answer, and there was a tendency to answer in accordance with the most recently uttered part of the comparison question. These results indicate that although retarded children are thoroughly acquainted with certain aspects of language and its use in the process of comparison, other important aspects have yet to be learned.