Seeing the disappearance of unseen

Because of the massive amount of incoming visual information, perception is fundamentally selective. We are aware of only a small subset of our visual input at any given moment, and a great deal of activity can occur right in front of our eyes without reaching awareness. While previous work has shown that even salient visual objects can go unseen, here we demonstrate the opposite pattern, wherein observers perceive stimuli which are not physically present. In particular, we show in two motion-induced blindness experiments that unseen objects can momentarily reenter awareness when they physically disappear: in some situations, you can see the disappearance of something you can't see. Moreover, when a stimulus changes outside of awareness in this situation and then physically disappears, observers momentarily see the altered versionöthus perceiving properties of an object that they had never seen before, after that object is already gone. This phenomenon of`perceptual reentry' yields new insights into the relationship between visual memory and conscious awareness. 1 Introduction Many experiments over the past few decades have uncovered surprising situations in which observers fail to become aware of salient objects and events in their visual fields. Many such phenomena occur in the context of various types of perceptuaìblindnesses', The hallmark of these effects is the inability to consciously perceive physically present visual information. Here we employ a different type of blindness ömotion-induced blindness (MIB)öto explore the opposite type of effect, wherein we do consciously perceive visual information which is not physically present. In MIB, a salient target is presented along with a complex global motion patternö for example a bright-yellow disc presented along with a rotating grid of blue crosses (see figure 1). When observers maintain fixation, a novel form of perceptual blindness occurs: the yellow disc fluctuates into and out of awareness (Bonneh et al 2001). Even slowly moving targets will disappear in this manner, ruling out a simple account based on adaptation, and local interactions between the grid and the target are not required, since MIB also occurs when the background motion never overlaps the target region