The Effects of Perceptual Transformation Experiences and Numerical Operational Experiences on Numerical Correspondence and Equivalence.

Piaget's theoretical and empirical accounts of young children's development of an understanding of numerical correspondence and equivalence has stimulated extensive research and analysis. A critical examination of a wide variety of training reports indicates that in a majority of the successful investigations, subjects have possessed some aspects of the conservation response (i.e., the ability to establish one-to-one correspondence or the ability to conserve on one but not two items) prior to their inclusion in the study. In the unsuccessful studies, subjects have been generally classified as "nonconservers" without specification of developmental status. This nonspecific classification suggests that children at lower stages of development (i.e., unable to establish one-to-one correspondence) were included in the sample. A second interesting observation is that although training sessions