Eye movements of monkey observers viewing vocalizing conspecifics

Asif A. Ghazanfar, Kristina Nielsen, Nikos K. Logothetis

Research output: Contribution to journalArticlepeer-review

56 Scopus citations


Primates, including humans, communicate using facial expressions, vocalizations and often a combination of the two modalities. For humans, such bimodal integration is best exemplified by speech-reading - humans readily use facial cues to enhance speech comprehension, particularly in noisy environments. Studies of the eye movement patterns of human speech-readers have revealed, unexpectedly, that they predominantly fixate on the eye region of the face as opposed to the mouth. Here, we tested the evolutionary basis for such a behavioral strategy by examining the eye movements of rhesus monkeys observers as they viewed vocalizing conspecifics. Under a variety of listening conditions, we found that rhesus monkeys predominantly focused on the eye region versus the mouth and that fixations on the mouth were tightly correlated with the onset of mouth movements. These eye movement patterns of rhesus monkeys are strikingly similar to those reported for humans observing the visual components of speech. The data therefore suggest that the sensorimotor strategies underlying bimodal speech perception may have a homologous counterpart in a closely related primate ancestor.

Original languageEnglish (US)
Pages (from-to)515-529
Number of pages15
Issue number3
StatePublished - Oct 2006
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Experimental and Cognitive Psychology
  • Developmental and Educational Psychology
  • Cognitive Neuroscience
  • Language and Linguistics
  • Linguistics and Language


  • Auditory cortex
  • Bimodal
  • Crossmodal
  • Evolution of speech
  • Eye gaze
  • Frontal eye fields
  • Lip-reading
  • Multisensory
  • Primate cognition
  • Scanpath
  • Speech reading
  • Superior temporal sulcus


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