Abstract
The purpose of this study was to investigate the use of color to guide attention to subsets of stimuli in search tasks. Previous work from our lab and others suggests that color information can be used efficiently to select subsets of stimuli to be attended. A12-alternative forced choice method was used. 12 stimuli were presented briefly (200msec.) on a white background at randomly jittered locations within an annular region centered on a fixation point. On each trial the target stimulus was assigned a higher S chromaticity and appeared slightly bluer than the rest of the stimuli. Observers were asked to indicate the bluish target by placing the cursor at its location and depressing the mouse button. In experimental conditions either 2. 4. or 6 randomly chosen stimuli were white and the remaining stimuli were assigned a saturated red ( high L) chromaticity. Observers were instructed that the bluish increment would be added to one of the white stimuli and that the red stimuli could be ignored. Psychometric functions obtained by plotting percent correct against the magnitude of the S increment in these conditions were compared with psychometric functions obtained in control conditions in which only 2, 4, 6, or 12 white stimuli were presented. Results showed that 4 observers could successfully ignore the red stimuli in the experimental conditions. An irrelevant red distractor was selected as a possible target location on less than 3% of trials. Psychometric functions in experimental conditions were very similar to those obtained in control conditions of the same set size. Results suggest that the use of feature information to guide attention is more flexible than suggested by the spotlight or zoom lens analogies of visual attention, which suggest that attention can only be directed to a unitary spatial area.