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Hoon Choi, Brian J Scholl; Effects of grouping and attention on the perception of causality. Journal of Vision 2003;3(9):544. doi: 10.1167/3.9.544.
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© 2015 Association for Research in Vision and Ophthalmology.
Beyond perceiving patterns of motion in simple dynamic displays, we can also perceive higher level properties such as *causality*, as when we see one object *collide* with another object. Though causality is a seemingly high-level property, its perception — like the perception of faces or speech — often appears to be automatic, irresistible, and driven by highly constrained and stimulus-driven ‘rules’. Our goal, following Michotte, is to discover these rules. Consider a disc (A) which moves toward a stationary disc (B) until they are adjacent, at which point A stops and B starts moving along the same path. We perceive this event as a ‘launch’: A smashes into B, causing its motion. When A and B fully overlap before B starts moving, however, the display is ambiguous: in addition to launching, observers often perceive a ‘pass’ wherein a single moving object simply passes over another stationary object. In a series of experiments, we demonstrate that perceptual grouping and attention can heavily influence whether such ambiguous events are perceived as causal. When a single additional disc (C) is added to the display, its motion can determine the percept. When C always stays aligned with B, subjects reliably perceive A & B as causal launching; when C always remains stationary (even after B moves), subjects reliably perceive A & B as noncausal passing. In this and many related experiments which we will demonstrate, we thus show that grouping induced by either connectedness or common motion can influence causal perception. We further suggest that such grouping effects are mediated by attention, and in other experiments we directly demonstrate that attention can both promote and attenuate causal perception. Like Michotte, we find that the perception of causality is mediated by strict visual ‘rules’. Beyond Michotte, we find that these rules operate not only over the objects involved in an event, but over additional objects, constrained by the allocation of attention.
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