Huichao Ji¹ (), Brian Scholl¹; ¹Yale University

Suppose you go jogging while wearing a ring on your finger, and earphones in your ears. Will the ring fall off, or will the earphones fall out? The answers will depend not so much on the relation itself (‘on’, ‘in’), but on the degree to which the ring/earphones fit *tightly* vs. *loosely*. This distinction is so important that it can even have lexical priority — e.g. in Korean, where you might use the same term to indicate putting a ring *on* your finger, or earphones *in* your ears, as long as the fit is similarly tight. Given the power of this distinction, might it also be prioritized even in visual processing? To find out, we exploited the logic of *categorial perception*, with simple animations of a cylinder moving down into a container. English speakers viewed sequential pairs of such events, and simply reported whether they were identical, vs. different in any way. Both the cylinder and the container could vary in diameter across animations, to implement tight fits (e.g. narrow cylinders moving into narrow containers) or loose fits (e.g. narrow cylinders moving into wide containers). Observers were much better at noticing Cross-Type changes (e.g. from a tight-fit to a loose-fit animation) than Within-Type changes (e.g. two different tight-fit animations), even though (1) the tight/loose distinction was always task-irrelevant, and (2) Within-Type changes were always greater in objective magnitude. Moreover, these results were specific to the tight vs. loose fits themselves, since these effects disappeared when the same movements (and sizes) occurred in the context of occlusion (where fit is irrelevant) instead of containment (where fit is consequential). This work thus demonstrates a new form of intuitive physics that may serve as an underlying visual primitive for dynamic event perception.