Using an experimental paradigm of crossmodal mediated stimulus equivalence to teach elementary reading comprehesion, the following problems will be investigated: Pure stimulus mediation of new stimulus equivalence (e.g., printed words and pictures) via receptive channels vs. active or implicit response mediation via oral names; the facilitation of crossmodal stimulus equivalences via language vs. the facilitation of language by crossmodal equivalences; the role of stimulus-response and stimulus-stimulus equivalences in the generation of unpracticed language forms; the development of effective methods for teaching the basic stimulus equivalences involved in simple reading comprehension; precise delineation of the conditions under which children display reading-reversal problems. Research is also proposed on stimulus control and learning in neurological mutants, animals of known genetic constitution and inherited CNS disease.