Charles H. Brown Joan M. Sinnott Regina A. Kressley
Dept. of Psychol., Univ. of South Alabama, Mobile, AL 36688
Four Sykes' monkeys (Cercopithecus albogularis) and three humans discriminated among 12 chirps presented in a repeating background paradigm. The test stimuli consisted of sets of four chirps recorded from Sykes' monkeys, red-tailed monkeys (Ce. ascanius), and small East African birds, respectively. Reaction times were submitted to a multidimensional scaling analysis (ALSCAL). All monkey listeners perceived the bird chirps as similar to each other, and distinct from the monkey calls, while two of the three human listeners had difficulty distinguishing the bird chirps from the monkey calls. Both human and monkey subjects tended to exhibit overlapping maps for the Sykes' and red-tailed calls, but the magnitude of overlap tended to be greatest for the monkey listeners. Guenon monkeys give chirps in similar alarm contexts, and these calls alert members of sympatric species to common dangers. Conversely, bird chirps are very commonly heard, are not associated with alarm, and must constitute for monkeys an acoustical impediment to communication. The present data suggest that the monkey's perceptual map of these highly similar calls is influenced by the biological significance of these calls in nature. [Work supported by NIDCD.]