Abstract
The perception of shape, it has been argued, also often entails the perception of time. A cookie with a bite taken out of it, for example, is seen as a whole cookie that was subsequently bitten. Similarly, a twisted towel is represented as an untwisted towel that was subsequently twisted. It has never been clear, however, whether such observations truly reflect visual processing alone. To explore this, we tested whether the perception of history in static shapes is powerful enough to influence the perception of other visual features. Observers were told that they would see short movies of a shape (e.g. a square) changing from its complete form into a truncated form, with a "piece" of it missing, and that this change could occur in two ways: (1) all at once, in a single flash; or (2) gradually, with the missing piece quickly "growing" into the shape (as when you poke your finger into a lump of clay). Our primary manipulation involved the contours of the missing piece itself. On some trials, these contours implied a causal history: the static result looked as if another shape had at one time 'intruded' on the original shape. On other trials, these contours implied no such past gradual transformation. When presented as an actual change (from the full shape to the truncated shape), this variable influenced whether observers actually perceived motion. In particular, when the contours of the missing piece suggested a type of historical 'intrusion', observers actually saw that intrusion occur: it appeared as if the change actually occurred gradually, in a type of transformational apparent motion. (Catch trials with real gradual motion ruled out the possibility of a response bias.) Thus the perception of causal history in shapes is powerful enough to induce illusory motion percepts.
Meeting abstract presented at VSS 2015