Automatic reinforcement and automatic punishment in infant vocal behavior.

Two female infants, aged 11 and 14 months, were exposed to a procedure in which an experimenter-emitted vocal response was paired with an established form of reinforcement (positive condition). One of the subjects was also exposed to a procedure in which an experimenter-emitted vocal response was paired with a neutral stimulus (neutral condition), and a procedure in which an experimenter-emitted vocal response was paired with a mild aversive stimulus (negative condition). An AB design was used with pre- and post-pairing measures. The results showed that after the positive pairing the targeted responses increased in frequency in 75% of the sessions. Responding remained constant during the neutral condition, but dropped sharply in the negative condition. These data suggest that a critical variable related to an infant's native language acquisition is the stimulus-stimulus pairing process that occurs when parents or caretakers speak to their infants.