Lua Koenig

Classic change blindness is the phenomenon where seemingly obvious changes which coincide with visual disruptions (such as blinks or brief blanks) go unnoticed by an attentive observer. Some early work into the causes of classic change blindness suggested that any pre-change stimulus representation is overwritten by a representation of the altered post-change stimulus, preventing change detection. However, recent work revealed that even when observers do maintain memory representations of both the pre- and post-change stimulus states, they can still miss the change, suggesting that change blindness can also arise from a failure to compare the stored representations. Here we study slow change blindness, a different but related phenomenon that occurs even in the absence of visual disruptions when the change occurs sufficiently slowly, to determine whether it could be explained by conclusions from classic change blindness. Across three different slow change blindness experiments we found that observers, who consistently failed to notice the change, had access to at least two memory representations of the changing display. One representation was precise but short-lived: a relatively detailed representation of the more recent states of slow-change display, but fragile. The other representation lasted longer but was fairly general: stable but too coarse to differentiate the various stages of the changing display. These findings suggest that although multiple representations are formed, the failure to compare hypothesis might not explain slow change blindness; even if a comparison were made, the representations formed would be either too sparse (longer term stores) or too fragile (short-lived stores) for such a comparison to be informative about a change.