Centre-surround relative motion and the freezing rotation illusion

Area of Science:

• Visual perception
• Psychophysics
• Motion perception

Background:

• The Freezing Rotation illusion describes a stationary perception of a rotating stimulus against a sinusoidally moving background.
• Previous hypotheses linked this illusion to induced motion from relative velocity differences between stimulus and background.

Purpose of the Study:

• To investigate the underlying mechanisms of the Freezing Rotation illusion.
• To test the hypothesis that the illusion magnitude correlates with the velocity difference between stimulus and background.

Main Methods:

• Presenting a rotating stimulus against backgrounds with constant and sinusoidal velocity profiles.
• Analyzing perceived velocity under conditions of same-direction, opposite-direction, and stationary backgrounds.

Main Results:

• The Freezing Rotation illusion persists even when the background moves at a constant velocity.
• A consistent underestimation of stimulus velocity occurs when stimulus and background move in the same direction.
• A consistent overestimation of stimulus velocity occurs when stimulus and background move in opposite directions or the background is stationary.
• The magnitude of velocity under/overestimation is independent of the velocity difference between stimulus and background.

Conclusions:

• The hypothesis linking the Freezing Rotation illusion to relative velocity differences is refuted.
• The illusion is characterized by fixed biases in velocity perception, not directly proportional to velocity disparities.
• Further investigation into factors influencing these fixed perceptual biases is warranted.