Ambiguous apparent motion in exchanging disks

Area of Science:

• Psychology
• Visual Perception
• Motion Perception

Background:

• Ambiguous visual stimuli can lead to different perceptual outcomes.
• The ratio of object sizes influences how motion is perceived.

Purpose of the Study:

• To investigate how the ratio of radii (r/R) between a large and small disk affects perceived motion.
• To determine the perceptual threshold for distinguishing between apparent motion and expansion/contraction.

Main Methods:

• Presenting observers with two side-by-side disks of different radii (R and r) undergoing repetitive motion at 1.33 Hz.
• Systematically varying the ratio r/R to observe changes in visual perception.
• Analyzing observer responses to the movement of the disks' centroid.

Main Results:

• When r/R < 0.8, observers perceive the large disk as moving back and forth over a static small disk.
• When r/R > 0.8, observers perceive two static disks that expand and contract out of phase.
• Perceived motion of the centroid is greatest when r/R < 0.8.

Conclusions:

• The ratio of radii is a critical factor in resolving the ambiguity of the presented visual stimulus.
• Perceptual outcomes shift from apparent motion to expansion/contraction as the r/R ratio increases.
• Observer responses are directly correlated with the calculated centroid movement, highlighting its role in motion perception.