Visual reversals and biases while observing ambiguous spinning biological motion and rigid structure-from-motion

Area of Science:

• Visual perception
• Computational neuroscience
• Cognitive psychology

Background:

• Ambiguous visual stimuli can lead to bistable perception, where observers perceive one of two alternating interpretations.
• Structure-from-motion (SFM) and biological motion are key paradigms for studying depth perception and perceptual reversals.

Purpose of the Study:

• To investigate how shape and motion characteristics influence perceptual reversal rates and biases in ambiguous point-light displays.
• To compare biases across different types of motion-defined depth stimuli, including biological motion and rigid/non-rigid SFM.

Main Methods:

• Observers viewed four point-light stimuli: a point-light walker (PLW), a spinning human figure, a spinning half-cylinder, and a wobbling cylinder.
• Analysis of angular reversal distributions to quantify facing-the-viewer (FTV), convexity, and depth-symmetry biases.
• Correlation analyses to identify shared perceptual mechanisms.

Main Results:

• The PLW exhibited the highest reversal rate and a strong FTV bias, with bimodal observer responses.
• Rigid SFM stimuli showed varying degrees of FTV and convexity/edge-in-front biases.
• The wobbling cylinder had the fewest reversals and no angular bias, suggesting persistent depth asymmetry or disrupted adaptation.
• Shared mechanisms were identified among spinning stimuli but not with the wobbling cylinder.

Conclusions:

• Shape and motion dynamics jointly modulate perceptual reversals in bistable perception.
• Findings refine models of visual perception, highlighting the role of stimulus properties and individual variability.
• The study identifies novel biases, such as the 'edge-in-front' bias, in SFM perception.