The vocal behavior of five children was recorded and analyzed during pre-and post-pairing conditions. Between these conditions there was a pairing condition where a target sound, word, or phrase was paired with an established form of reinforcement (e.g., tickling). In the first experiment all of the children emitted the targeted responses during the post-pairing condition. The results showed that the children acquired new vocal and verbal responses by pairing neutral stimuli with established forms of conditioned or unconditioned reinforcement. Perhaps the most significant aspect of these results was that new vocal responses were acquired by the children without the use of direct reinforcement, echoic training, or prompts. In the second experiment several parameters of the pairing procedure were examined. The results of the two experiments have implications for the analysis of native language acquisition, and for the development of language intervention procedures for individuals who fail to acquire language.Most children around the world readily acquire their parent's or caretaker's language, despite the fact that no special instruction is provided. This phenomenon, typically identified as native language acquisition, has generated a substantial amount of research and controversy (e.g., Chomsky, 1959;Skinner, 1957). What makes this universal event intriguing is that native language acquisition occurs only early in life, and only for a first lan-The authors gratefully acknowledge the assistance of Cassie Braam,