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Jessica Madrid, Corbin Cunningham, Arryn Robbins, Hayward Godwin, Jeremy Wolfe, Michael Hout; Exploring the nature of mental representations in hybrid visual and memory search. Journal of Vision 2016;16(12):341. doi: https://doi.org/10.1167/16.12.341.
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© ARVO (1962-2015); The Authors (2016-present)
To search for targets in scenes filled with distractors, observers must utilize mental representations ("templates") for those targets (e.g. where are my keys). While previous research on "hybrid search" has demonstrated that observers can search for any of hundreds of distinct targets, little is known about the internal representation of those targets. Is each target stored individually or can related targets form prototypes that speed search? To address this question, observers performed hybrid search for a memory set of 30 target types in two conditions (blocked, counterbalanced order). In the "categorical" condition, observers searched for footwear and strollers. A small category was defined by five exemplars of either footwear or strollers; a large category, by 25 of the other. In the "mixed" condition, target types were drawn from 30 different categories. Five were arbitrarily assigned to a "small" artificial category and 25 to a "large" category. After the pictures were memorized, observers searched for any of the 30 targets (160 trials, 50% target present). Distractors came from various categories that did not overlap with any targets. Reaction times were faster in the categorical condition; unsurprising, since observers needed only to determine if an item was footwear or a stroller. More interestingly, RTs were faster for the larger category (even after controlling for prevalence: 3175 ms vs 3481ms). This effect was reduced for the mixed condition. We hypothesize that, with natural categories, 25 exemplars allowed observers to create a more useful prototype than just five exemplars. This effect is minimal or absent with artificial, arbitrary categories; at least given the level of practice experienced by our observers. Overall, this work demonstrates that, when searching for a set of items within a given category, the utility of a prototype is dependent on the number of items used to form that prototype.
Meeting abstract presented at VSS 2016
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