Discrimination of isolation peep variants by squirrel monkeys

Responses to variant forms of the isolation peep have been studied by behavioral techniques in a group of eight squirrel monkeys. Discrimination learning with variant pairs using shock avoidance methods was surprisingly fast, and equivalence testing without differential reward revealed that variant forms are spontaneously discriminated by captive squirrel monkeys. Evidence was obtained that features occurring in the first third of the isolation peep are more effectively utilized in choice behavior than features occurring in the last third. It is postulated that such features are part of a communicative system in this species.