Dynamic categorical memory distortion from "visual verbs".

We see the world not only in terms of features and objects (such as the color or shape of a ball), but also in terms of a set of abstract "event types" (such as a ball swinging or bouncing). This form of categorical perception occurs spontaneously during passive viewing, as a part of visual processing itself - even when task-irrelevant, and even when verbal encoding is discouraged or disrupted. Here we demonstrate that such representations yield an adaptive type of dynamic categorical memory distortion, based on the different predictions afforded by different event types. This was inspired by the idea that the purpose of perception is not only to characterize the present ("What's out there?") but also to predict the future ("What's about to happen?"). Observers viewed animations of a moving ball, and reported its final position after the display disappeared. Critically, the same trajectories were displayed in the context of visual events such as swinging vs. tossing, or bouncing vs. rolling. These categorical event types had powerful systematic influences on visual memory, e.g. with less horizontal (but not vertical) motion extrapolation for swinging, compared to tossing - since a swinging ball is limited in how far it can travel before reversing its trajectory. And careful controls showed that this depended on the event types themselves, rather than any lower-level properties. Memory for dynamic information is thus distorted in adaptive ways by the operation of 'visual verbs' - effectively changing what is encoded based on categorical predictions about how events will unfold.