Abstract
Flanker congruency experiments show that an irrelevant stimulus can affect the judgment of a second, relevant stimulus. It is unclear whether this effect is due to dependencies between the processing of relevant and irrelevant stimuli before selection, or due to failures of selection on some fraction of trials. In order to investigate the cause of the flanker congruency effect, we combined the flanker and spatial filtering paradigms. As in the flanker paradigm, we mapped a set of colored disks to different response sets creating congruent and incongruent conditions; as in the spatial filtering paradigm (Yigit-Elliott, Palmer, & Moore, 2011), we presented a target and a flanker in the periphery as opposed to presenting the target near the fovea and the flanker in the periphery. This way, the target and flanker were interchangeable, and only differed in location. This assures that any congruency effect is due to selective attention rather than sensory processes alone. We varied the contrast to measure psychometric functions and examined both large and small separations between the target and flanker (1° or 11.3°). There were three critical conditions: the target and flanker were identical (identical); the target and flanker required the same response (response congruent); and, the target and flanker required different responses (response incongruent). For large separations, accuracy was the same for all conditions. For small separations, accuracy was the same for the identical and response congruent conditions. The flanker congruency effect was found only in the response incongruent condition and only on the asymptote of the psychometric function. The threshold was the same in all conditions when defined relative to the asymptote. These results are consistent with a theory that assumes all-or-none selection and independent processing before selection. In such a theory, the stimulus that is not selected (unattended) has no effect on behavior.
Meeting abstract presented at VSS 2012