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Mary Portillo, James Pomerantz; Search asymmetries with emergent features. Journal of Vision 2007;7(9):911. doi: 10.1167/7.9.911.
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© ARVO (1962-2015); The Authors (2016-present)
Building on our work on emergent features (EFs), we looked for further evidence that EFs behave as basic features in human vision. EFs arise when simpler elements combine in Gestalt groups, and they are diagnosed by configural superiority effects (CSEs), wherein discrimination between two elements becomes better when informationless context is added. Since our task involves the search for an odd quadrant among three identical ones (where targets are presented alone or with uninformative context in singleton and composite conditions respectively) the possibility of search asymmetries (SAs) arises. Indeed, our data from experiments using dot patterns show that proximity, orientation, linearity, symmetry, surroundedness and inside/outside relationship produce SAs. For example, for orientation, finding a diagonally-related pair of dots among vertical or horizontal pairs is faster than the reverse. Similarly, with linearity, finding a nonlinear arrangement of three dots among linear arrangement is faster than its opposite. We note how in some cases the search asymmetry is present in the single dot condition, suggesting that the asymmetry does not emerge from the added context and highlighting the importance of pinpointing the real source of the asymmetry, a factor that should be taken into account when looking at any search asymmetry. Most importantly, in other cases we find SAs in composite conditions when there is none in the equivalent singleton condition. Moreover, in some cases the direction of the search asymmetry is reversed when a new EF is created even though the original signal remains constant. Indeed in one extreme case we discovered a triple reversal in the direction of asymmetry as additional context was added. Last, we present search asymmetry information for more complex EFs produced with lines rather than dots. In all, we take the presence of SAs with EFs as further evidence that EFs behave as basic in vision.
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