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Abstract:
Primates use auditory and visual cues to process the vocal communication signals produced by members of their species. For human speech, facial cues are known to enhance perception of speech under noisy conditions. That is, if speech has to be followed at high background noise levels, the ability to see a talker’s face enhances intelligibility. Recently, studies have examined the eye movement patterns of humans while viewing talkers under varying levels of naturalistic background noise (Vatikiotis-Bateson et al. (1998) Perception Psychophysics 60: 926). Under all noise conditions, human perceivers mostly fixate the eye region, followed by the mouth region, but as the background noise increases, they increase their number of fixations on the mouth region. To characterize potential behavioral homologies between monkey and human vocal communication, we have been investigating the eye movement patterns of rhesus monkeys while they view digitized videos of conspecifics producing vocalizations under three different background noise levels. We are analyzing how the simultaneous presentation of a dynamic facial expression and its corresponding vocalization influences the gaze patterns of monkey observers. Such data will give us insights into the evolution of sensory and motor mechanisms used in primate vocal communication.
