Temporal integration in two species of Old World monkeys: blue monkeys (Cercopithecus mitis) and grey-cheeked mangabeys (Cercocebus albigena).

Changes in auditory sensitivity as a function of signal duration were studied in two species of Old World monkeys. Testing was conducted under free-field conditions with pure tones 250, 800, 1600, and 4000 Hz in frequency. Test stimuli ranged in duration from 35-2000 ms. The results showed that the temporal integration functions for the blue monkeys were similar to those reported for rhesus monkeys [T. D. Clack, J. Acoust. Soc. Am. 40, 1140-1146 (1966)], but differed significantly from those for mangabey monkeys and human subjects tested in the same apparatus, by the same procedure. Integration functions for humans and mangabeys did not differ. It was concluded that some taxonomic groups of primates exhibit temporal integration times that are much longer than those characteristic of humans, while others do not, and that interspecific differences in temporal integration are not readily related to species differences in their vocal repertoires.