Discriminative conditioning of vocalizations in Lemur catta

Abstract Two lemurs ( Lemur catta ) received food reward for each vocalization of certain types emitted during 30-min sessions for 20 days. A light stimulus then was introduced for periods totalling half of each session, and only vocalizations made while the light was off were reinforced. Finally, the conditions were reversed and reward followed vocalizations only during the light-on periods. Both animals showed a moderate increase in responses during the continuous-reinforcement situation. In the discrimination situation (and its reversal) response-rate and latency measures showed appropriate differences in behaviour under the two stimulus conditions. The relation to other studies of animal vocalization and its manipulation by reinforcement is discussed.