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Hoon Choi, Brian J. Scholl; The Temporal Dynamics of Causal Perception. Journal of Vision 2004;4(8):571. doi: 10.1167/4.8.571.
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© 2016 Association for Research in Vision and Ophthalmology.
In simple dynamic events we can perceive not only motion, but also higher-level properties such as *causality*, as when we see one object *collide* with another. The perception of causality often appears to be automatic and driven by highly constrained and stimulus-driven ‘rules’, and ever since Michotte a major project has been to uncover the nature of these rules. Here we take up a different project: beyond determining *what* information affects causal perception, we explore the temporal dynamics of *when* such effects occur. We do so by exploiting a recent dynamic grouping effect discovered by Choi and Scholl (in press): when an object (A) moves toward a stationary object (B) until they overlap completely, at which point A stops and B starts moving, observers can easily perceive noncausal ‘passing’, wherein one moving object passes over another. When another stationary object (C) is added to the display aligned with B, observers still see A and B as noncausal passing. In contrast, when C moves along with B, observers now perceive A and B as causal ‘launching’. In our previous work, C always moved in perfect synchrony with B; here, in contrast, it sometimes moved a bit earlier or later, with this temporal offset varied parametrically. Surprisingly, we found that C's motion can induce causal perception even when it begins *after* the full-overlap between A and B. This illustrates a type of ‘postdictive’ perception: our conscious perception of the world is not an instantaneous moment-by-moment construction, but rather is formed by integrating information presented within brief extended temporal windows. Such effects have been previously demonstrated for low-level motion phenomena, but the present results demonstrate that postdictive processes can also influence higher-level event perception. These findings help to characterize not only the stimulus-driven ‘rules’ employed in causal perception, but also the temporal dynamics of how and when they operate.
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