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Abstract:
Johansson’s point-light walker figures remain one of the most powerfuland convincing examples of the role that motion can play in the perceptionof form. How exactly does our visual system take a few isolated points oflight and provide us with such compelling impressions of human action?Here I present data from a series of studies demonstrating that biologicalmotion processing can come to rely almost exclusively on EITHER bottom-up or top-down processing mechanisms. Using a dual-task paradigm Iwill show that when attention is allocated to a demanding secondary task(change detection), direction discrimination performance drops from nearceiling levels (85% plus), when walkers are masked by randomly movingelements, to complete chance (50%), when more complex, scrambled walker masks are used. This dissociation under dual-task conditions adds furtherweight to the suggestion that the high, single-task performance commonlyreported with both random and scrambled masks is achieved via verydifferent, yet equally effective, processing mechanisms. A second series ofstudies will further explore the role of attention during biological motionprocessing using standard visual search techniques. In conclusion, I willargue that the effective use of both high and low-level integration strategiesis highly adaptive, given the ecological significance of human and animalaction, and may well be at the core of what appears to make biologicalmotion “special”.
