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J Vis. 2017 Sep 1;17(11):5. doi: 10.1167/17.11.5.

One visual search, many memory searches: An eye-tracking investigation of hybrid search.

Author information

1
University of Utah, Salt Lake City, UT, USA.
2
University of Oxford, Oxford, UK.
3
Brigham and Women's Hospital, Boston, MA, USA.
4
Harvard Medical School, Boston, MA, USA.

Abstract

Suppose you go to the supermarket with a shopping list of 10 items held in memory. Your shopping expedition can be seen as a combination of visual search and memory search. This is known as "hybrid search." There is a growing interest in understanding how hybrid search tasks are accomplished. We used eye tracking to examine how manipulating the number of possible targets (the memory set size [MSS]) changes how observers (Os) search. We found that dwell time on each distractor increased with MSS, suggesting a memory search was being executed each time a new distractor was fixated. Meanwhile, although the rate of refixation increased with MSS, it was not nearly enough to suggest a strategy that involves repeatedly searching visual space for subgroups of the target set. These data provide a clear demonstration that hybrid search tasks are carried out via a "one visual search, many memory searches" heuristic in which Os examine items in the visual array once with a very low rate of refixations. For each item selected, Os activate a memory search that produces logarithmic response time increases with increased MSS. Furthermore, the percentage of distractors fixated was strongly modulated by the MSS: More items in the MSS led to a higher percentage of fixated distractors. Searching for more potential targets appears to significantly alter how Os approach the task, ultimately resulting in more eye movements and longer response times.

PMID:
28892812
PMCID:
PMC5596794
DOI:
10.1167/17.11.5
[Indexed for MEDLINE]
Free PMC Article

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