Demonstrated is a covariance principle that causes the observer to assume that if one aspect of a two-dimensional figure (its perimeter or its area) is conserved, the other aspect must also be conserved (pseudo-conservation). Mentally retarded individuals, assuming no such fixed relationship, correctly judged the changed state of the nonconserved…

Two studies are reported. The first is based on Piaget's assertion that the child's representation of his world is dependent on the level of cognitive development at which he is currently functioning. Forty-eight normals and 48 retardates were given a visual memory task. They were asked to recall a configural presentation in a number of ways,…

This research attempts to diagnose the skills required for successful spatial performance in order to provide a theoretical foundation for military training in such tasks as map reading, surveying, and navigation. It is known that successful performance on spatial tasks depends on task requirements (e.g., requisite knowledge, alternative paths to…