Food-reinforced yawning in Macaca tonkeana

An operant conditioning paradigm comprising continuous food-reinforcement, fixed-ratio responding, and extinction procedures was used to evaluate the possibility that adult male macaques can control their rate of yawning. Two non-food-deprived Macaca tonkeana quickly learned to produce yawns for food rewards. They also increased the rate of production according to fixed-ratio requirements, and showed initial response peaks followed by diminished rates of yawning during extinction. The results indicate that adult male macaques can yawn voluntarily. Further work along these lines may help distinguish among different types of yawning as indicated in the literature.