title: Biological motion perception is cue-invariant.
abstract: Previous work investigating whether biological motion is supported by local second-order motion has been contradictory, with different groups finding either a difference or no difference in performance compared to that obtained with first-order stimuli. Here we show psychophysically, using randomized-polarity and contrast-modulated stimuli, that detection of second-order biological motion walkers is worse for stimuli defined by second-order cues, but this difference is explained by a difference in visibility of the local motion in the stimuli. By mixing first-order and second-order dots within the same stimulus, we show that, when the two types of dot are equally visible, first-order noise dots can mask a second-order walker, and vice-versa. We also show that direction-discrimination of normal, inverted and scrambled walkers follow the same pattern for second-order as that obtained with first-order stimuli. These results are consistent with biological motion being processed by a mechanism that is cue-invariant.
authors.affiliation: McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Quebec, Canada. craig.aaenstockdale@mcgill.ca
authors.forename: Craig
authors.initials: C
authors.lastname: Aaen-Stockdale
authors.forename: Benjamin
authors.initials: B
authors.lastname: Thompson
authors.forename: Robert F
authors.initials: RF
authors.lastname: Hess
authors.forename: Nikolaus F
authors.initials: NF
authors.lastname: Troje
mesh_terms: D000328:Adult; D016477:Artifacts; D003463:Cues; D004056:Differential Threshold; D004192:Discrimination, Psychological; D005260:Female; D006801:Humans; D008297:Male; D009039:Motion Perception; D010470:Perceptual Masking; D010775:Photic Stimulation / Q000379:methods; D011601:Psychophysics; D016138:Walking