A search asymmetry reversed by figure-ground assignment.
We report evidence demonstrating that a search asymmetry favoring concave over convex targets can be reversed by altering the figure-ground assignment of edges in shapes. Visual search for a concave target among convex distractors is faster than search for a convex target among concave distractors (a search asymmetry). By using shapes with ambiguous local figure-ground relations, we demonstrated that search can be efficient (with search slopes around 10 ms/item) or inefficient (with search slopes around 30-40 ms/item) with the same stimuli, depending on whether edges are assigned to concave or convex "figures." This assignment process can operate in a top-down manner, according to the task set. The results suggest that attention is allocated to spatial regions following the computation of figure-ground relations in parallel across the elements present. This computation can also be modulated by top-down processes.
Cognitive Science Research Centre, School of Psychology, University of Birmingham, B15 2TT, United Kingdom. g.w.humphreys@bham.ac.uk
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D001288:Attention; D004193:Discrimination Learning; D005364:Field Dependence-Independence; D006801:Humans; D009949:Orientation; D010364:Pattern Recognition, Visual; D011930:Reaction Time