Localization of primate calls by old world monkeys.

Monkeys (Macaca) were trained by operant conditioning techniques to report the minimum detectable change in location of a sound in space, and were tested with a series of recorded coo or clear call vocalizations. Acuity of localization varied from approximately 4 degrees to 15 degrees and was a function of the magnitude of the change in pitch (frequency modulation) of the different clear calls.