Merve Erdogan¹, Brian Scholl¹; ¹Yale University

One of the most impressive and well-known examples of the robustness of perception is biological motion: people reliably see locomoting agents from only a handful of moving dots, in point-light walkers (PLWs). But PLWs are also robust in another, even more impressive way: people reliably see biological motion even when the dot arrangements vary dramatically in size from moment to moment. Like biological motion itself, this has been attributed to special features of *bodies* — which always maintain the same constrained skeletal structure, and engage in characteristic cyclic motion patterns (e.g. pendular motion when walking). Recently, however, many of the most foundational features of biological motion (e.g. spontaneous perception, resistance to noise, disruption by spatial scrambling, and extensions to rich secondary properties) have also been observed for a very different form of non-rigid motion: point-light *cloths* (PLCs) — as when a ribbon (or a sheet on a clothesline) is waving in the wind. Are PLCs similarly robust? To find out, we showed people point-light displays of dynamic soft materials that changed radically from moment-to-moment in both size (as in previous PLW research) and location (not previously explored). Despite these constant drastic changes, people still reliably and spontaneously perceived the motions of cloths. We demonstrate this in a series of both psychophysical experiments and phenomenological demonstrations, and we show how this also extends to secondary properties such as cloth stiffness. These results are perhaps even more impressive than with PLWs, since cloths can vary dynamically so much more than bodies (due to the lack of any skeletal structure or cyclical motion). This form of robust perception in point-light displays is not specific to bodies after all, but may rather reflect more general mechanisms of extracting structure from nonrigid motion, perhaps incorporating intuitive physical constraints.