Visual memories can fade not only due to interference and decay, but also due to ‘active forgetting’. Perhaps the most salient example of this involves visual event segmentation: both recognition and recall decline when observers experience event boundaries (e.g. when a visual feature suddenly changes, or when they see themselves pass through a doorway while walking down a long hallway). Such effects are often assumed to be adaptive: event boundaries are taken as cues that the statistics of the world are likely to have changed, rendering pre-boundary memories obsolete. In previous work, however, the event boundaries have always been explicit, with pre- and post-boundary stimuli having similar or identical visual statistics. Here we reversed this pattern: is active forgetting triggered even by completely unnoticed changes in implicit visual statistics, without any overt segmentation cues? Subjects viewed a list of pseudowords for 5 seconds, and later their recognition memory was tested. Critically, they viewed a sequence of images between study and test that either did or did not contain an event boundary defined purely by changes in implicit statistics. Inspired by studies of visual statistical learning, images consisted of differently colored dots positioned within a 3x3 grid. Images contained spatial regularities in the dots’ relative positions despite randomized absolute positioning (such that a red dot was always directly above a blue dot, e.g.). For some subjects, these spatial statistics remained constant; for others, they changed midway through the sequence. Even when subjects were unaware of the implicit statistical patterns, those patterns still influenced resulting memory performance — with impaired recognition (as measured by d’) for subjects who viewed sequences with a change in statistics. Thus, active forgetting due to event segmentation does not depend on observers consciously noticing event boundaries, but rather reflects the underlying architecture of visual working memory.

In the ‘oddball effect’, a single object which grows in size (in a sequence of otherwise-static objects) appears to last longer. Here we explore the temporal resolution of this effect: is oddball-induced time dilation specific to the oddball itself? Observers viewed sequences of static colored discs with a single oddball, and across trials reproduced various discs’ durations. We observed time dilation not only for the oddball disc itself, but also for the immediately following (but not preceding) disc. Oddballs may orient attention not only to the present moment, but also to what is about to unfold next.