Results are discussed in terms of Piaget's concept of the parallel development of the cognition of the impersonal and interpersonal worlds. (Authors)

Lower-class children required significantly more training task repetitions to learn a conservation task than did middle-class children. (Authors)

A single administration of the reversal learning paradigm is not a sufficient basis for determining either a given subject's choice of option or his behavior on its constituent learning measures. This conclusion raises many questions about past research relating to mediation theory, since this paradigm has been the basic one employed. (Authors)