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Johan Hulleman; Misguided: how knowing the orientation of the target can make you worse at visual search. Journal of Vision 2016;16(12):1318. doi: 10.1167/16.12.1318.
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© ARVO (1962-2015); The Authors (2016-present)
Hulleman & Olivers (BBS, in press) have proposed a fixation-based theoretical framework for visual search, where performance is determined by the Functional Visual Field (FVF). Target-present decisions are based on statistics pooled across the FVF. In easier tasks the FVF covers multiple items, whereas the FVF reduces to a single item in very difficult search. This framework predicts qualitative differences in guidance by orientation. For difficult search, knowing the target orientation should help, since saccades to individual ineligible items can be avoided. For easier search this is not possible and the presence of differently orientated, ineligible items in the FVF may interfere with the computation of the pooled statistics. Sixteen participants searched for a T amongst L (medium search) and for a specific configuration of squares (difficult search), in counterbalanced blocks. In the 100% eligibility condition all items had the same orientation as the target. In the 50% eligibility condition only half of the items shared the target orientation. The other half could be rejected based on their different orientation. There were three display sizes: 6, 12 and 18 items. For difficult search, knowing the orientation of the target improved performance when eligibility went from 100% to 50%. Search slopes decreased both on target-absent trials and on target-present trials. For medium search however, performance deteriorated. The slopes increased both on target-present and on target-absent trials. So, orientation knowledge made difficult search better, but made medium search worse. This supports Hulleman & Olivers' framework. In very difficult search the FVF encompasses only a single item. This allows the use of orientation knowledge to avoid saccades to ineligible items. In medium search, the FVF encompasses multiple items. This means that it is not possible to selectively target eligible items, since several of the other items that fall within the FVF may be ineligible.
Meeting abstract presented at VSS 2016
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