Abstract
The perception of causality in Michotte-type launch events (one disk moves towards another, then stops while the other starts moving in the same direction) is reduced in response to visual adaptation (a negative aftereffect), allowing us to experimentally dissect the mechanisms underlying the visual detection of cause and effect. Here, we determine whether launches with different motion directions, speeds, motion kinematics and conjunctions between motion direction and color result in transfer of adaptation to constrain the computations underlying the perception of causality. In four experiments, we presented simple launch events, varying in the degree of overlap when the first disk stopped and the second started moving (zero to full overlap in seven steps), and asked observers to indicate whether one disk caused the second disk to move or whether the first disk passed the stationary one. To characterize observers’ perception of causality, we fitted psychometric functions to each individual’s reports as a function of overlap, both before and after the repeated exposure to an adaptor. We observed strong negative aftereffects across all experiments. Observers were less likely to report a causal launch following adaptation when adaptor and test events had similar characteristics. First, adaptation was specific to the direction of the adapting stimulus (Experiment 1). Second, both slow and fast launches resulted in adaptation with transfer across the two motion speeds (Experiment 2). Third, a single disk—replaying the motion kinematics of a two-disk launch—resulted in adaptation, albeit smaller than for events with two disks (Experiment 3). Finally, in launches composed of disks with different colors, adaptation transferred across colors while the adaptation was again selective for motion direction (Experiment 4). These findings provide compelling evidence that the perception of causality is closely linked to motion processing in that the underlying computations are embedded within motion-direction selective channels.