A nonspatial sound modulates processing of visual distractors in a flanker task

Successful navigation of information-rich, multimodal environments involves processing both auditory and visual information. The extent to which information within each modality is processed varies because of many factors, but the influence of auditory stimuli on the processing of visual stimuli in these multimodal environments is not well understood. Previous research has shown that a preceding sound leads to decreased reaction times in visual tasks (Bertelson, Quarterly Journal of Experimental Psychology 19(3), 272-279, 1967). The current study examines whether a nonspatial, task-irrelevant sound additionally alters processing of visual distractors that flank a central target. We used a version of a flanker task in which participants responded to a central letter surrounded by two irrelevant flanker letters. When these flankers are associated with a conflicting response, a congruency effect occurs such that reaction time to the target is slowed (Eriksen & Eriksen, Perception & Psychophysics, 16(1), 143-149, 1974). In two experiments using this task, results showed that a preceding tone caused general speeding of reaction time across flanker types, consistent with alerting. The tone also caused decreased variation in response time. Critically, the tone modulated the congruency effect, with a greater speeding for congruent flankers than for incongruent flankers. This suggests that the influence of flanker identity was more intense after tone presentation, consistent with a nonspatial sound increasing perceptual and/or response-association processing of flanking stimuli.