Effects of grouping and attention on the perception of causality.

Beyond perceiving patterns of motion in simple dynamic displays, we can also perceive higher level properties, such as causality, as when we see one object collide with another object. Although causality is a seemingly high-level property, its perception--like the perception of faces or speech--often appears to be automatic, irresistible, and driven by highly constrained and stimulus-driven rules. Here, in an exploration of such rules, we demonstrate that perceptual grouping and attention can influence the both perception of causality in ambiguous displays. We first report several types of grouping effects, based on connectedness, proximity, and common motion. We further suggest that such grouping effects are mediated by the allocation of attention, and we directly demonstrate that causal perception can be strengthened or attenuated on the basis of where observers are attending, independent of fixation. Like Michotte, we find that the perception of causality is mediated by strict visual rules. Beyond Michotte, we find that these rules operate not only over discrete objects, but also over perceptual groups, constrained by the allocation of attention.