Visual comparisons within and between object parts: evidence for a single-part superiority effect

Area of Science:

• Cognitive Psychology
• Computational Neuroscience
• Visual Perception

Background:

• Understanding how the human visual system segments objects into parts is crucial for object recognition.
• Curvature extrema along contours are hypothesized to play a role in defining object boundaries and parts.

Purpose of the Study:

• To investigate the role of contour curvature and part-boundary perception in visual segmentation.
• To determine if concave curvature extrema, indicative of part boundaries, affect perceptual judgments differently than convex extrema.

Main Methods:

• Participants judged the sameness of two marks on curved contours.
• Stimuli varied in curvature (concave vs. convex) and target separation.
• Stimulus duration and curvature magnitude were manipulated.

Main Results:

• Decision latencies were longer when targets straddled a concave extremum (part boundary) compared to a convex extremum.
• This 'single-part superiority effect' increased with stimulus duration and contour curvature.
• The effect diminished when the global configuration did not support a part-boundary interpretation.

Conclusions:

• Concave curvature extrema significantly influence visual segmentation by signaling object parts.
• Global object organization plays a critical role in how the visual system decomposes objects into parts.
• These findings highlight the interplay between local contour features and global structure in visual perception.