Stereopsis loses dominance over relative size as target separation increases

Area of Science:

• Visual perception
• Depth perception
• Computational neuroscience

Background:

• Binocular disparity is a key cue for stereoscopic depth.
• Target separation can influence the effectiveness of stereoscopic depth cues.
• Relative size also provides information about relative depth.

Purpose of the Study:

• To investigate how target separation affects the dominance of binocular disparity versus relative size in determining perceived depth.
• To determine if separation itself, or fixation changes, is critical for the shift in cue dominance.

Main Methods:

• Four experiments were conducted using varying target separations.
• Stimuli were presented under conditions with and without fixation changes (sequential vs. brief presentations).
• Target separation was manipulated at different retinal eccentricities.

Main Results:

• Disparity dominated depth perception at small separations (0.42-0.5 degrees) under both fixation conditions.
• Relative size increasingly dominated as separation increased, particularly with brief presentations (0.75-1 degree).
• Separation per se was identified as the critical factor for the cue dominance switch, not fixation changes.

Conclusions:

• Relative disparity exerts a compulsory influence on perceived depth at small target separations.
• The mechanisms governing depth perception may differ for small versus large target separations.
• Stereoscopic dominance at small separations aligns with immunity to stereoscopic reversals.