How do rhesus monkeys ( Macaca mulatta) scan faces in a visual paired comparison task?

Area of Science:

• Primate cognition
• Comparative psychology
• Neuroscience

Background:

• Humans and monkeys exhibit a novelty preference when presented with familiar and novel stimuli.
• Understanding visual processing in non-human primates offers insights into facial recognition mechanisms.

Purpose of the Study:

• To analyze visual exploration patterns (scanpaths) in monkeys during a visual paired comparison task.
• To determine which facial features are attended to in familiar versus novel monkey faces.
• To quantitatively assess perceptual processes in spontaneous visual face exploration.

Main Methods:

• Monkeys performed a visual paired comparison task with familiar and novel images (objects, faces, inverted faces, different expressions).
• Scanpaths and looking preferences were recorded and analyzed.
• Eye movements were precisely measured to assess visual attention.

Main Results:

• Monkeys consistently showed a longer looking time for novel faces, regardless of expression or orientation.
• The eyes were the most frequently scanned facial feature across all conditions.
• Monkeys scanned unique expressive features when viewing emotional faces, like a fear grimace.

Conclusions:

• Non-human primates demonstrate a clear novelty preference in facial recognition.
• Visual analysis of faces by primates is systematic and quantifiable, with a focus on key features.
• Scanpath analysis provides a robust method for studying primate visual perception of complex stimuli.