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Corbin Cunningham, Jeremy M. Wolfe; Finding what is new in hybrid visual and memory search: a new search asymmetry.. Journal of Vision 2012;12(9):721. doi: 10.1167/12.9.721.
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© ARVO (1962-2015); The Authors (2016-present)
In many visual search tasks, we search for any of several targets (Are any of the members of my English class here in the school cafeteria?). Such tasks are "hybrid" visual and memory searches. Wolfe (2012) found that RTs in hybrid tasks increase linearly with the visual set size but logarithmically with the memory set size. Using photos of objects, this logarithmic relationship was demonstrated for memory set sizes up to 100. In those experiments, observers search for the item that was in the memory set. What would happen if observers searched for the item that was not in the memory set? In classic visual search, the absence of a feature is often harder to find than its presence. Would such an asymmetry be seen in hybrid search? We asked observers to locate the one new item in a visual display that contained 6 or 12 displayed items, as distractors. Obviously, an item can only be new once. Thus, once observers found the new item, they were told to remember it; meaning that the memory set size increased by one on each trial. 12 observers were tested for 600 trials. Unsurprisingly, error rates rise as the memory set size rises but only to 12% for memory sets of 500-600 items. RT remains a linear function of log(memory set). Moreover, the slopes of the memory set functions in this experiment closely match those of the previous hybrid search experiment. However, the mean RTs are significantly slower than predicted from prior experiments. This suggests that it takes longer to make a decision that an item is the new target among old distractors than it does to decide that this is the old target among new distractors. In hybrid search, novelty does not pop-out.
Meeting abstract presented at VSS 2012
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