Adding rotation to translation: percepts and illusions.

Area of Science:

• Visual perception
• Motion perception
• Object recognition

Background:

• Human observers often perceive object motion differently than the actual physical dynamics.
• Understanding visual perception of combined translation and rotation is key to visual processing.

Purpose of the Study:

• To investigate how object rotation affects the perception of linear translation.
• To determine the factors influencing the switch between veridical and illusory motion perception.

Main Methods:

• Presenting observers with objects undergoing simultaneous linear translation and rotation.
• Analyzing observer judgments of motion and trajectory under varying object orientations and shapes.
• Measuring perceived motion directions to extrapolate perceived trajectories.

Main Results:

• Illusory curved trajectories are perceived when object orientation remains within a limited range relative to translation.
• Perceptual switches to veridical linear motion with rotation occur when orientation sufficiently deviates from the translation axis.
• The critical angle for this switch depends on object elongation, with lines being more prone to illusory curved perception than squares.

Conclusions:

• Perception can transition between illusory curved and veridical linear motion for the same object.
• Object shape and orientation relative to translation are critical factors in motion perception.
• Findings have implications for understanding real-world scenarios involving complex object motion.