Taped Vocalization as a Reinforcer of Vocal Behavior in a Siamang Gibbon (Symphalangus Syndactylus)

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Abstract
The experiment demonstrated operant control of the vocal behavior of an adult male siamang by using taped vocalizations of wild siamangs as the reinforcer. The procedure consisted of 38 sessions divided into five phases. Baseline (three sessions): taped vocalizations were presented continuously until the subject made two vocal responses, then were terminated entirely. Operant 1 (five sessions): following elicitation of vocal behavior, taped vocalizations were presented contingently on any vocal response by the subject. Operant 2 (nine sessions): a 5-min. elicitation period preceded the onset of the contingency period. Discrimination-extinction (12 sessions): the 5-min. elicitation period was followed by an extinction period in which no taped answering calls were presented. Reconditioning (nine sessions): the procedure was identical to that for Operant 2. During all phases, the session continued until the subject ceased emitting vocal responses. Mean times spent calling for the last three sessions of each phase were: Baseline, 0.0 (min.); Operant 1, 1.60; Operant 2, 6.50; Discrimination-extinction, 3.56; and Reconditioning, 6.71. The results represent the operant control of a prepotent, species-typical pattern of behavior by use of a reinforcing stimulus that is specifically relevant to that behavior.