Global shape processing: which parts form the whole?

Area of Science:

• Visual perception
• Computational neuroscience
• Psychophysics

Background:

• Radial frequency (RF) patterns are complex visual stimuli.
• Previous research indicated global shape processing and corner importance in RF pattern detection at threshold.
• These findings were limited to stimuli near the circle discriminability threshold.

Purpose of the Study:

• To investigate if supra-threshold RF patterns are processed as global shapes.
• To identify critical features for RF pattern shape representation.
• To explore the contribution of specific shape components (maxima, inflections) to global perception.

Main Methods:

• Utilized RF pattern adaptation paradigm with supra-threshold stimuli.
• Measured perceived amplitude shifts in RF test patterns after adaptation.
• Employed adaptation to whole patterns versus adaptation to component parts (concave maxima, convex maxima, inflections).

Main Results:

• Adaptation to the whole RF pattern produced greater perceived amplitude shifts than adaptation to component parts.
• Adaptation to individual shape components (concave maxima, convex maxima, inflections) yielded similar magnitude aftereffects.
• This suggests that while the whole is greater than the sum of its parts, individual features contribute equally.

Conclusions:

• Supra-threshold RF patterns are processed as global shapes.
• Concave maxima, convex maxima, and inflections contribute equally to global shape processing.
• Appearance-based tasks with supra-threshold stimuli are crucial for revealing feature contributions in shape perception.