Here it comes: Active forgetting triggered even just by anticipation of an impending event boundary.

Visual input arrives in a continuous stream, but we often experience the world as a sequence of discrete events - and the boundaries between events have important consequences for our mental lives. Perhaps the best example of this is that memory not only declines as a function of elapsed time, but is also impaired when crossing an event boundary - as when walking through a doorway. (This impairment may be adaptive, as when one "flushes" a cache in a computer program when completing a function.) But when exactly does this impairment occur? Existing work has not asked this question: based on a reasonable assumption that forgetting occurs when we cross event boundaries, memory has only been tested after this point. Here we demonstrate that even visual cues to an impending event boundary (that one has not yet crossed) suffice to trigger forgetting. Subjects viewed an immersive animation that simulated walking through a room. Before their walk, they saw a list of pseudo-words, and immediately after their walk, their recognition memory was tested. During their walk, some subjects passed through a doorway, while others did not (equating time and distance traveled). Memory was impaired (relative to the "no doorway" condition) not only when they passed through the doorway, but also when they were tested just before they would have crossed the doorway. Additional controls confirmed that this was due to the anticipation of event boundaries (rather than differential surprise or visual complexity). Visual processing may proactively "flush" memory to some degree in preparation for future events.