Abstract
Though visual input arrives in a continuous stream, our perceptual experiences unfold as a sequence of discrete events. This form of visual event segmentation has important consequences for our mental lives. For example, memory is disrupted not only by elapsed time, but also by crossing an event boundary. Even an activity as simple as walking through a doorway can effectively 'flush' memory (just as one might empty a cache in a computer program), perhaps because this is when the visual statistics of our local environments tend to change most dramatically -- and it may be downright maladaptive to hold on to now-obsolete information. But just when does this 'flushing' occur? At the very moment we cross the boundary? When we encounter new post-boundary information? Here we provide what may be a surprising answer: even just the *anticipation* of an impending event boundary is sufficient to flush memory. Observers viewed an immersive 3D animation in which they walked down a long virtual room. Before their virtual walk, they saw a list of pseudo-words, their recognition memory for which was then tested immediately after the walk ended. Two of the conditions were inspired by past work: during their walk, some observers passed through a doorway, while others traversed the identical path through a room that had no such event boundary. Critically, we also tested a third condition, in which memory was probed just before the observers would have crossed through the doorway -- while carefully equating for elapsed time by manipulating the doorway's location. Relative to the baseline no-doorway condition, we observed reliable memory disruptions in *both* the 'doorway' and 'anticipation' conditions -- and additional control experiments confirmed that this was due to anticipation of the event boundary (and not just surprise). Visual processing thus *proactively* flushes memory by anticipating future events.