Humans Perceive Binocular Rivalry and Fusion in a Tristable Dynamic State

Area of Science:

• Neuroscience
• Vision Science
• Perception

Background:

• Human vision integrates information from both eyes, leading to either fused perception or binocular rivalry.
• Fusion and rivalry are often studied as mutually exclusive processes.
• The relationship between fusion and rivalry, and whether they are distinct or part of a unified system, remains unclear.

Purpose of the Study:

• To investigate whether fusion and binocular rivalry are separate perceptual processes or sub-states of a single dynamical system.
• To determine the perceptual outcomes of Gabor patches with varying interocular orientation disparities.

Main Methods:

• Human observers viewed Gabor patches with a range of interocular orientation disparities.
• Participants reported their perceptual experience over time, noting fused, rivalrous (left-eye or right-eye dominant), and uncertain states.
• Statistical models were tested against the observed perceptual data.

Main Results:

• A dynamic tristable zone was identified (approximately 25-35° orientation disparity) where fused, left-eye, and right-eye dominant percepts coexisted.
• The temporal dynamics of fusion and non-fusion periods during this zone resembled other bistable perceptual phenomena.
• A simple three-state bistable model successfully reproduced many of the observed results, outperforming models treating fusion and rivalry as separate processes.

Conclusions:

• Binocular rivalry and fusion are not separate, mutually exclusive processes but rather multistable sub-states within a single dynamical system.
• These sub-states can directly compete, leading to dynamic perceptual shifts.
• This finding offers a unified framework for understanding how the visual system reconciles conflicting retinal inputs.