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Masaki Fukuchi, Naotsugu Tsuchiya, Christof Koch; The focus of expansion in optical flow fields acts as a strong cue for visual attention. Journal of Vision 2009;9(8):137. doi: 10.1167/9.8.137.
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During walking or driving, the optical flow field FOR an observer expands from a singular point, called the focus of expansion (FOE; assuming negligible rotation). Does this point in the field of view attract significant amount of task-independent attention? We reported last year at VSS that observers' overt attention (i.e., eye movements) was strongly drawn to the FOE, both when viewing natural scenes as well as in visual search. The effects were stronger and remained longer than any other cues tested (intensity, color, flicker, perspective, contractive motion). We here further investigate these effects. (1) Using an exogenous cueing paradigm, we found that convert attention was also attracted by the FOE, but not by a focus of contraction (FOC; zooming out). The FOE effects on covert attention was observed early on (SOA = 0) and remained strong (up to SOA=750 msec), without showing the typical time course for “inhibition of return”. (2) Using a natural scene change detection paradigm, we found that the distribution of attentional monitoring of objects was strongly biased by the FOE; when the FOE was near a changed object, the RT was [[gt]] 3 sec faster than when the FOE was far from the change (p.9, KS-test). (3) We compared the performance of the saliency model of visual attention (Itti & Koch, 2001) with or without the FOE component. By incorporating the FOE component, the model predicted the human eye movements significantly better. We conclude that the FOE guides visual attention and eye movements in our daily life.
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