The space contraction asymmetry in Michotte's launching effect

Previous studies have found that, compared with noncausal events, spatial contraction exists between the causal object and the effect object due to the perceived causality. The present research aims to examine whether the causal object and the effect object have the same effect on spatial contraction. A modified launching effect, in which a bar bridges the spatial gap between the final position of the launcher and the initial position of the target, was adopted. Experiment 1 validates the absolute underestimation of the bar's length between the launcher and the target. Experiment 2a finds that in the direct launching effect, the perceived position of the bar's trailing edge that was contacted by the final launcher was displaced along the objects' direction of movement. Meanwhile, the perceived position of the bar's leading edge that was contacted by the initial target was displaced in opposite direction to the moving direction. The magnitude of the former's displacement was significantly larger than that of the latter, displaying a significant contraction asymmetry. Experiment 2b demonstrates that the contraction asymmetry did not result from the launcher remaining in contact with the edge of the bar. Experiment 3 indicates that contraction asymmetry showed a type of postdictive effect; that is, to some extent, this asymmetry depends on what happens after contact. In conclusion, the space between the causal object and effect object contracts asymmetrically in the launching effect, which implies that the causal object and effect object are perceived as shifting toward each other nonequidistantly in visual space.