A new paper from our lab came out today in the journal Psychological Science. It deals with inversion effects in biological motion perception and the role that motion plays in the recognition of point-light displays.
What's new and exciting about it? The paper demonstrates that a very common task which has been used countless times in biological motion research can be accomplished with high accuracy by a human observer without having to rely at all on the ability to recover the non-rigid structure of the articulated body of the depicted person.
The latter – the ability to recover the structure of the deforming body from the way it moves – has been the explicit subject of much research in the field. Different sorts of task have been used to accomplish that. In a particularly popular one, the observer is asked to indicate the direction (left or right) into which a stationary point-light walker is facing. We had shown before that this is possible to some degree with completely scrambled biological motion (Troje & Westhoff, 2006), but the comparatively low response accuracies nevertheless argued for a dominance of structural cues.
In this new study, we introduce a new kind of stimulus which is scrambled only to a degree necessary to deprive it from any horizontal asymmetry that could cue facing direction from structural information. As in the fully scrambled walker, the only hints to facing direction are in the local motion of individual trajectories. The difference between the new stimulus and the previously used ones is that we kept the vertical order of the individual dots intact. Specifically, the dots representing the feet are still on the ground and the ones representing the head it still at the top. While this change doesn't add any information about facing direction in itself, it makes the information present in the stimulus much more accessible to the observer. It “validates” the directional cues contained in the particular movement of the feet.
A new interactive demo allows the user to play with the stimuli used in this experiment.
The paper is authored by Masahiro Hirai who spent two years as a postdoc in our lab and two former graduate students, Daniel Saunders and Dorita Chang, who both left for new positions in other labs after their recent graduation.
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Welcome to the BioMotionLab! Directed by Dr. Niko Troje we are a research lab located at Queen's University in Kingston, Ontario.
Our work is focused on questions involving the processing of sensory information, perception, cognition and communication. Enjoy this web site and find out much more about us and our work.
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