Changes in visual speed perception induced by anticipatory smooth eye movements.

Area of Science:

• Neuroscience
• Ophthalmology
• Perception Science

Background:

• Observer expectations influence anticipatory smooth eye movements (ASEMs) and visual perception.
• Previous research showed discrete effects of expectations on ASEM and perception but couldn't isolate ASEM's impact.

Purpose of the Study:

• To directly investigate the effect of ASEM execution on visual speed perception.
• To differentiate the influence of ASEM from other expectation-driven factors on perception.

Main Methods:

• A two-alternative forced-choice (2AFC) task was employed.
• Participants tracked sequential visual motion stimuli and judged the speed of the second stimulus relative to the first.
• Eye movements, including ASEM velocity and steady-state eye velocity, were monitored.

Main Results:

• Visual speed perception shifted based on ASEM velocity, even with comparable steady-state eye velocities.
• Perceptual judgments correlated with retinal slip velocity during the initial phase of ocular tracking.
• ASEM execution led to an underestimation of visual speed.

Conclusions:

• ASEM significantly impacts visual speed perception, causing an underestimation of velocity.
• The effect is linked to reduced retinal slip velocity in the initial tracking phase, not steady-state performance.
• This study provides psychophysical evidence for the crucial role of initial ocular tracking dynamics in visual speed perception.