SOCIAL AND NONSOCIAL CONDITIONING OF INFANT VOCALIZATIONS1

Abstract

Basic to most views on the modification of an infant's early vocalizing are the stimuli afforded by the caretaker's behavior for the control of such social behavior (3, 5, 6). Rheingold, Gewirtz, and Ross (7) found that an adult's responses contingent on the vocalizing of 3-month-old infants could bring about an increase in that behavior. Subsequently, when the reinforcing stimuli (tactual contact, tsk sounds, and smiles) were omitted during two days of extinction, the vocal rate declined to a level about i8 per cent above the operant rate. As Rheingold et al. point out, however, the question of whether vocalizing was operantly conditioned is equivocal since the reinforcing stimuli, per se, may have acted as social releasers. The possibility exists, then, that response-independent and dependent social events may have both stimulating and reinforcing properties for infant vocal behavior. Moreover, vocalizations may be affected by the presence in the infant's visual environment of a relatively unfamiliar and unresponding adult. That is, an immobile adult may serve as a discriminative stimulus for vocal behavior. Finally, if the infant's vocalizing effects any stimulus change in his external environment, then even such physical events (as well as social ones) might reliably strengthen the behavior. The present investigation attempted to explore these possibilities by testing the effects of a series of short term experimental manipulations on the vocal behavior of infants.