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Florent Levillain; When two causes compete for the same effect: How the visual system deals with different streams of event.. Journal of Vision 2012;12(9):157. doi: https://doi.org/10.1167/12.9.157.
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In an attempt to uncover some of the rules governing event perception, we designed a case of causal competition in which two events can both be perceived as causing a third event. A launching effect occurred when a red disc (B), after being contacted by a black disc (A), started to move immediately with the same speed and in the same direction as A. In the same sequence, a pulling effect could manifest when a purple square (C), placed bellow B, initiated its movement just before B, and moved in unison with it for a certain duration. Thus, A and C competed to be considered as the cause for B's movement. To weaken or give strength to one of the possible causal representations, we varied the delay separating A and B's trajectories, as well as the distance covered by C. We asked observers to determine which of the two potential causes, launching or pulling, was the most compelling, or if none of them was striking. We found that the launching effect was dominant for most of the distances travelled by C. However, this dominance tended to recede when a sufficient delay was introduced at the time of collision. Ultimately, the transition from a launching representation to a pulling representation took place when the delay separating the two components of the launching sequence was equal to 300 ms and when C covered half of B's total distance. The dominance reversed completely in favor of an impression of pulling when C accompanied B until B stopped. These results expose a "phase transition point", when the amount of evidence in favor of a cause supersedes the evidence in favor of the other. They gesture towards a study of the specific inferences drawn to process the temporal and causal order of a scene.
Meeting abstract presented at VSS 2012
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