The Attentional Window Modulates Capture by Audiovisual Events Erik Van der Burg*, Christian N. L. Olivers, Jan Theeuwes Department Cognitive Psychology, Vrije Universiteit, Amsterdam, The Netherlands Abstract Visual search is markedly improved when a target color change is synchronized with a spatially non-informative auditory signal. This ‘‘pip and pop’’ effect is an automatic process as even a distractor captures attention when accompanied by a tone. Previous studies investigating visual attention have indicated that automatic capture is susceptible to the size of the attentional window. The present study investigated whether the pip and pop effect is modulated by the extent to which participants divide their attention across the visual field We show that participants were better in detecting a synchronized audiovisual event when they divided their attention across the visual field relative to a condition in which they focused their attention. We argue that audiovisual capture is reduced under focused conditions relative to distributed settings. Citation: Van der Burg E, Olivers CNL, Theeuwes J (2012) The Attentional Window Modulates Capture by Audiovisual Events. PLoS ONE 7(7): e39137. doi:10.1371/ journal.pone.0039137 Editor: Joy J. Geng, University of California, Davis, United States of America Received January 12, 2012; Accepted May 18, 2012; Published July 10, 2012 Copyright: 2012 Van der Burg et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This research was supported by a NWO-VIDI grant (452-06-007) to CNLO. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: e.van.der.burg@psy.vu.nl Introduction Every day we receive a bulk of information from different sensory modalities. It has been extensively demonstrated that these sensory inputs interact when presented in either close temporal or spatial proximity (see e.g. [1,2], for recent reviews). So far, most studies investigating multisensory interactions have used sparse displays, often involving a single visual event in combination with a single auditory event at a time (see e.g. [3,4]. Whereas these studies were successful in reporting multisensory interactions, they say little about how we behave and integrate information from different sensory modalities in a competing environment (see also [5], for this argument). Recently we have shown that auditory and tactile signals can affect the competition among multiple visual events in dynamic environments [6,7]. In the Van der Burg et al. [6] study, participants searched for a horizontal or vertical line segment among up to 48 other distractor line segments of various orientations, all continuously changing color. We found that both search time and search slopes were drastically reduced when the target color change was accompanied by an auditory signal compared to a condition in which no such signal was present (see also [8]). This audition driven visual search benefit, which we called the ‘‘pip and pop’’ effect, was observed even though the auditory signal was uninformative about the orientation, color and, most important, the location of the synchronized visual target. One might argue that the auditory signal acted as a temporal cue. The tone may have informed participants about when the target changed color, so that it became easier to find. However, in follow-up experiments we found evidence that the search benefits were not due to temporal cueing. For instance, we presented similar temporal information by briefly making the fixation dot disappear or by briefly presenting a peripheral halo when that visual target changed color. In both cases, the temporal cue did not affect visual search performance at all, while, in a control experiment, we showed that these temporal visual cues were effective temporal warning signals (see also Van der Burg et al. 2008b for a detailed discussion about temporal cueing). In a subsequent study, we measured event-related brain potentials (ERPs) to investigate the underlying neural mechanism of the pip and pop effect [9]. In the Van der Burg et al. (2011) study, we reported that the search benefits correlated with an early (50–60 ms) multisensory interaction over the left parieto-occipital cortex. This early multisensory interaction was then followed by an early (80–100 ms) modulation over the occipital areas contralateral to the synchronized visual target, and an enhanced N2pc (,200 ms), indicating that the synchronized visual event was affected by the auditory signal and as a result captured attention, respectively. Interestingly, a similar early multisensory interaction as well as a reliable modulation over the occipital cortex and N2pc were observed in the case that a task irrelevant distractor change was accompanied by an auditory signal, suggesting that the pip and pop effect occurred in a stimulus-driven, automatic fashion (see also [6,10]). The presence of an early multisensory interaction in the case that a single distractor was synchronized with an auditory signal bolsters the claim that the pip and pop effect is not due to temporal cueing, since the tone was never synchronized with the target in these distractor blocks, and participants were aware of this. In other words, there was no need for participants to attend to the auditory signal, and to use the onset of the auditory signal as a time marker. Even though the above results provide behavioral as well as neurophysiological evidence that synchronized audiovisual events capture attention in an automatic manner (see also [11]), some results suggest that the capture by such events is not as strong as previously reported attentional capture effects within purely the PLoS ONE | www.plosone.org 1 July 2012 | Volume 7 | Issue 7 | e39137