One versus two eyes makes a difference! Early face perception is modulated by featural fixation and feature context

Area of Science:

• Neuroscience
• Cognitive Psychology
• Visual Perception

Background:

• The N170 event-related potential is a key neural marker for face perception.
• Previous studies indicate the N170 is sensitive to eye regions and fixations within faces.

Purpose of the Study:

• To investigate the N170's sensitivity to isolated facial features versus features fixated within a face.
• To compare neural responses to single eyes versus eye regions.

Main Methods:

• Used a gaze-contingent procedure to measure N170 responses to isolated features and features within a face.
• Controlled for pixel intensity and contrast at global and local levels.
• Compared N170 to single eyes and bilateral eye regions.

Main Results:

• Fixating eyes within a face elicited larger N170 amplitudes than fixating mouths or noses, indicating higher-order processing.
• Isolated features produced larger and more delayed N170 responses than when fixated within a face.
• Eye regions consistently elicited larger and shorter N170 responses than single eyes, especially for contralateral content.

Conclusions:

• The N170's eye sensitivity reflects complex perceptual processes, not just low-level effects.
• The N170 response suggests a neural system tuned to detect eye regions (two symmetric eyes) rather than individual eyes.
• Findings highlight the crucial role of the eyes in early face perception and suggest a specialized neural detector for eye regions.