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Stephen R. Mitroff, Brian J. Scholl; Online Grouping and Segmentation Without Awareness: Evidence from Motion-Induced Blindness. Journal of Vision 2004;4(8):201. doi: 10.1167/4.8.201.
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The visual system must parse and group the incoming input into discrete units, but it has proven difficult to determine when and how this occurs. Here we show that both object and group representations can be formed, disrupted, and updated without awareness. We do so using the phenomenon of motion-induced blindness (MIB), wherein salient and attended objects will fluctuate into and out of conscious awareness when superimposed onto certain global moving patterns. Previous research has shown that both objecthood and grouping influence MIB. For example, two discs will tend to enter and leave awareness simultaneously if grouped into a single unit (even by cues such as proximity), but will otherwise tend to undergo MIB independently. Here we alter various segmentation and grouping cues while two discs are unseen during MIB, and find that such changes influence whether the discs reappear independently. For example, adding a line to form a dumbbell during MIB causes two discs to reenter awareness together. Similarly, when the connecting line of an initial dumbbell is removed during MIB, the discs reappear independently. These results indicate that object representations can be formed and disrupted outside of awareness. Similar effects occur with grouping cues such as proximity. Observers viewed three evenly-spaced discs in a horizontal line, and reported when all three disappeared due to MIB. At this point — while the discs were present but unseen — a single randomly chosen disc gradually faded out, leaving two discs which were either close together or separated. Separated discs tended to reenter awareness independently, whereas neighboring discs reappeared simultaneously, indicating that their grouping strength had been revised outside of awareness. In these and several other examples, we illustrate how MIB can be used as a tool to determine the importance of conscious awareness for several types of visual processing.
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