Fig. 5.

Time-course of looking time duration in a habituation-recovery experiment. A: Subjects were habituated with different Barbary macaque alarm call exemplars given in response to a human observer, and then tested with a call given in response to a dog after a variable number of habituation trials, depending on the behavior of the subject. After the subject had failed to respond in three trials, the test call was broadcast. The looking time shows a clear rebound of the animals' interest. B: As before, subjects were habituated with calls given in response to the human observer, and then tested with a novel call from the same category. The subjects showed no renewed interest. Data from Fischer [1998].