Interhemispheric transfer and the completion of reversible operations in non-conserving children.

Evidence that concerns interhemispheric transfer deficits in young children is reviewed, and it is suggested that the late maturation of the corpus callosum may prevent the transfer and thus verbal expression of knowledge concerning equivalence relationships in non-conservers - operations normally performed by the right hemisphere. Because previous findings with "split-brain" patients indicate that interhemispheric transfer can be achieved when questions are phrased in the context of a reward (e.g., "preference"), questions concerning the conservation of a non-equivalent volume were posed to 65 non-conservers in terms of an imagined reward (preference condition). Questions also were phrased so as to require comparative-relational determinations as well as expectation of an empirical reversal of the stimulus conditions so as to determine differences/similarities in the reasoning process. Significantly more non-conservers demonstrated an awareness of empirical reversal or performed the preference relational operation correctly as compared to conditions that required comparative-relational judgments. The evidence also suggests the presence of two fundamentally distinct cognitive approaches to the problem, which appear to resist integration in children of this age group.