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Joo-Seok Hyun, Steven Luck; How fast is the search for a change in change detection?. Journal of Vision 2009;9(8):579. doi: https://doi.org/10.1167/9.8.579.
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We recently proposed a model of change detection in which observers search for the presence of a change between the test array and a visual working memory (VWM) representation of the sample array (Hyun, Woodman, Vogel, Hollingworth & Luck, in press). We found that the change detection occurs immediately after presentation of the test items regardless of set sizes, suggesting the search for a change occurs just like simple feature pop-out search. However, it has been unclear whether the search for a change can be completed as fast as a pop-out target is found in visual search. In the present study, we tested this idea by interfering with the search for a change. In the change detection task, with a fixed set size of four, we presented pattern masks 17ms after the test items with 100ms exposure duration (SOA 117ms). We recorded ERPs (N2pc) evoked by the test items. The masks are known to disrupt the process during which sample items in change detection are consolidated (Vogel, Woodman & Luck, 2006). The presence of N2pc indicates how good visual attention is focused to the location of a visual change. We compared the mean amplitude of N2pc from the trials with masks against those without masks, and found the N2pc amplitude was larger when without masks. The results indicate that the masks interfered with the pop-out of a change, and therefore focused attention was less evident. The search for a visual change appears very rapid but requires a certain amount of time at least longer than 117ms. The results support for the idea that the minimum amount of time needed for the search for a change is longer than pop-out visual search.
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