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Brian J. Scholl, Ken Nakayama; Causal capture: Contextual effects on the perception of collision events. Journal of Vision 2001;1(3):476. doi: 10.1167/1.3.476.
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© ARVO (1962-2015); The Authors (2016-present)
Consider an object A that moves toward a stationary object B until they are adjacent, at which point A stops and B starts moving along the same path. This can be seen as a causal event, where the momentum of object A is imparted to object B via a type of collision, so that B is ‘launched’. We report new contextual effects on such phenomena, and discuss several of the variables which mediate these effects. When A and B fully intersect before B's motion, observers see a ‘pass’: one object is simply seen to pass behind another stationary object. This acausal percept does not involve an event: there is no collision and no transfer of momentum, despite the fact that you clearly see both items change their featural properties when overlapped. In the presence of a distinct nearby launching event, however, this stimulus is ‘captured’: it too is now irresistibly seen as a collision, rather than a ‘pass’. This contextual capture requires that the context-event be present for only 100 ms surrounding the ‘impact’, but is destroyed by only 200 ms of temporal asynchrony. In addition to these and other spatiotemporal variables, we will discuss the effects of multiple competing contexts, and will also demonstrate cross-modal effects on this phenomenon, involving various types of auditory events which occur at or near the moment of possible ‘impact’. These results collectively help to define the conditions under which the visual system constructs percepts involving mechanical causality.
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