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Colin Conwell, George Alvarez; Your Visual System (Probably) Knows More Physics than You Do. Journal of Vision 2018;18(10):304. doi: https://doi.org/10.1167/18.10.304.
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© ARVO (1962-2015); The Authors (2016-present)
Humans have a finely calibrated ability to navigate physical environments characterized by complex objects in complex interactions, an ability often referred to as "intuitive physics." However, the extent to which our intuitive physics employs sophisticated computations (approximating Newtonian mechanical laws), as opposed to heuristic shortcuts, remains a matter of debate. Here we use a classic experimental paradigm to address this issue: a moving object collides with a stationary object, and observers decide which object is heavier based on the kinematics of the collision. This question can be answered perfectly using the conservation of momentum, from which one can derive the fact that the mass ratio (M1/M2) is proportional to the ratio of speed changes for each object before versus after the collision (DeltaV2/DeltaV1). Velocity-change-ratios less than 1 indicate that the first object was lighter, and ratios greater than 1 indicate that the first object was heavier. We generated displays such that the speed of only one object, or its speed change after collision, were insufficient for accurately judging which object was heavier — only by comparing the relative speed change could participants perform the task well. We find that participants could perform the task better when both objects were visible (M = .60, SEM = .02) than when the initially moving object was hidden (M = .50, SEM = .02, t(95) = 4.94 p < .001) or when the initially stationary object was hidden (M = .56, SEM = .02, t(95) = 2.48, p < .05). Thus, even though the movement of the second object alone was uninformative (performance at chance, p = .98), it could be usefully combined with the kinematics of the first object to make a more accurate judgment. These results suggest that our intuitive physics engine can use complex computations, like the conservation of momentum.
Meeting abstract presented at VSS 2018
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