Abstract
Previous studies have shown visual-auditory integration effects when the visual events are attended. For example, in the “sound-induced-flash illusion”, a single fully attended flash accompanied with two auditory beeps is perceived as two flashes (Shams, Kamitani, & Shimojo, 2002). The current study demonstrates that auditory cues can facilitate visual processing even when stimuli are unattended, and this facilitation can occur for both texture segregation (low-level) and the Simon effect (high-level). We adopted the inattentional blindness (IB) paradigm of Moore and Egeth (1997). In the texture segregation task, the unattended background pattern was formed by texture segregation of different oriented Gabors to render the railroad track as in the Ponzo illusion. The participants were asked to judge the length of the two horizontal lines. In the Simon task, the unattended background pattern was presented on the left or right side of the fixated target and the response to the target (left/right) is compatible or incompatible to the background pattern. In both tasks, a set of inquires was conducted to make sure that the background patterns were indeed unattended. Half of the trials were accompanied with a beep sound, and the other half were not. Results show that in trials with beep sounds, compared to those without, both the Ponzo illusion and the Simon effect are obtained, even when the participants are blind (i.e., IB) to the background pattern. These results suggest that unattended visual-auditory integration can occur at different locus through the processing stream.
Supported by the National Science Council of Taiwan, NSC95-2752-H-002-007-PAE and 95-2413-H-002-020