Integrating Biological Motion: The Role of Grouping in the Perception of Point-Light Actions

Ervin Poljac,Johan Wagemans,Karl Verfaillie

doi:10.1371/journal.pone.0025867

Abstract

The human visual system is highly sensitive to biological motion and manages to organize even a highly reduced point-light stimulus into a vivid percept of human action. The current study investigated to what extent the origin of this saliency of point-light displays is related to its intrinsic Gestalt qualities. In particular, we studied whether biological motion perception is facilitated when the elements can be grouped according to good continuation and similarity as Gestalt principles of perceptual organization. We found that both grouping principles enhanced biological motion perception but their effects differed when stimuli were inverted. These results provide evidence that Gestalt principles of good continuity and similarity also apply to more complex and dynamic meaningful stimuli.

Highlights

Human vision has highly efficient mechanisms to recognize actions of others rapidly and without apparent effort, even when the stimulus is defined solely by a few moving light points [1]
The current study investigated whether grouping is important for the perception of biological motion stimuli, for the integration of elements that constitute a pointlight walker
The results provide evidence that the recovery of the connectivity structure of a point-light figure is facilitated when the stimulus elements can be grouped according to Gestalt laws of perceptual organization

Summary

Introduction

Human vision has highly efficient mechanisms to recognize actions of others rapidly and without apparent effort, even when the stimulus is defined solely by a few moving light points [1]. How exactly the visual system manages to organize this highly reduced stimulus into a vivid percept of human action and what mechanisms are responsible for the perception of biological motion still puzzles vision scientists. Recent studies that have attempted to identify key features of the point-light stimulus largely focused on the importance of local motion signals for the perception of biological motion. Casile and Giese [2] argued that the integration of individual point-light elements into a percept of a walker might be accomplished by detecting mid-level motion features, while precise position information from the impoverished stimuli is not necessary (spatial localization is relatively coarse). Troje and Westhof [3] narrowed down the crucial features even further to the motion of the feet, which is essential in differentiating biological from non-biological motion [ 4,5]

Methods

Results

Conclusion