Visual motion of missing-fundamental patterns: motion energy versus feature correspondence

Area of Science:

• Visual perception
• Computational neuroscience
• Psychophysics

Background:

• Missing-fundamental gratings, derived from square-wave gratings by removing fundamental Fourier components, exhibit paradoxical backward motion perception.
• Current models of motion perception struggle to explain this phenomenon where features move forward, yet the grating appears to move backward.

Purpose of the Study:

• To investigate the motion perception of missing-fundamental gratings and plaids.
• To test the validity of existing motion perception models.
• To determine the role of the fundamental component and emergent features in perceived motion direction.

Main Methods:

• Utilizing variants of missing-fundamental gratings and plaids as visual stimuli.
• Systematically adding back fractions of the fundamental component to altered stimuli.
• Conducting experiments with chromatic gratings, plaids, and luminance barberpoles at approximate isoluminance.

Main Results:

• Missing-fundamental gratings and plaids were perceived to move backward.
• Adding small fractions of the fundamental component restored forward motion perception for both gratings and plaids.
• The critical amplitude of the fundamental required for forward motion was consistent across isolated gratings and plaids.
• Emergent features in plaids, like intersections, did not significantly contribute to perceived motion direction.
• Backward motion in chromatic and luminance variants was also reversed by fundamental addition.

Conclusions:

• The perception of motion direction in missing-fundamental stimuli is critically dependent on the presence of the fundamental Fourier component.
• Emergent features of complex stimuli like plaids play a minimal role in determining the perceived direction of motion.
• Findings challenge existing motion perception models and highlight the importance of Fourier components in visual motion processing.