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Mazyar Fallah, Illia Tchernikov; Attentional color hierarchy for pursuit target selection. Journal of Vision 2009;9(8):223. doi: https://doi.org/10.1167/9.8.223.
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© ARVO (1962-2015); The Authors (2016-present)
We performed 2 experiments to investigate the effect of color on object selection. In Experiment 1, subjects fixated on a central dot and an aperture with a single surface of colored dots, either red, green, blue or yellow, moving left or right at a constant speed of 6.0 deg/sec appeared in the periphery. After a random period of time, the fixation spot disappeared which was the cue for the subjects to saccade to the aperture. Saccading to the surface resulted in an automatic pursuit of that surface. Experiment 1 showed that color modulates motion processing as measured in smooth pursuit velocity for single surfaces.
Next, we investigated whether this color modulation was equivalent to a modulation of salience, by seeing whether target selection would be biased towards the color that produced a higher pursuit speed over a color that produced less pursuit speed. In Experiment 2, a second surface was placed in the aperture, moving at the same speed in the opposite direction and differing in color, and pursuit was again measured. If task-irrelevant color has no effect on salience and target selection, then pursuit would not be biased towards either surface of equal speed and contrast. In contrast, we found evidence of a selection hierarchy determining which surface was pursued: red [[gt]] green [[gt]] yellow [[gt]] blue. Furthermore, the strength of selection (pursuit speed) was strongly correlated with the distance in color space between the two colors. These results suggest a bottom-up attentional hierarchy based on color processing, similar to the bottom-up salience effects of contrast. This attentional color hierarchy intrinsically modulated other features of the object; more specifically the motion processing that drives smooth pursuit. Thus, color and motion are likely bound at or below the level of areas MT and MST, and color modulates bottom-up salience.
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