visual domain (e.g. for color [12] or for abrupt onset [13]). For instance, search slopes for targets in the synchronized conditions never approached zero (see e.g [6,7]), as would have been indicative of complete prioritization. Within the visual domain, Belopolsky and colleagues [14,15] recently provided evidence that the extent to which attention is divided across the visual field (referred to as the attentional window) modulates the degree to which salient events capture attention (see also [16]). In these studies Belopolsky and colleagues provided evidence for the idea proposed by Theeuwes ([17], p. 436) arguing that ‘‘top-down control over visual selection can be accomplished by endogenously varying the spatial attentional window’’ (see also [18,19]). Specifically, Belopolsky et al. [14] showed that salient singletons capture attention when participants adopt a large, diffuse attentional window (i.e. when participants attend to the whole display), while the same singletons do not capture attention when participants adopt a small, more focused attentional window (i.e. when participants attend to the center of the screen only) (see also [20–22]). It is possible that the size of the visual attentional window also plays a role in the pip and pop effect. For example, if, on some trials, observers adopt a relatively small attentional window (e.g. due to a distractor color change that captures attention), they may miss the visual target event (if it is located outside their attentional window), generating relatively long search times on some trials (since participants must wait for the subsequent audiovisual event to occur). The present study was designed to investigate whether the size of the attentional window has an effect on the extent to which audiovisual events capture attention. Experiment 1 Participants searched for a target letter S or H among distractor letters. Importantly, before searching, participants were asked to memorize a letter S or H (the cue), which was necessary to make a correct response. Participants were asked whether the target in the search display was the same letter as the cue or a different letter. The important manipulation involved the size of the cue. In the diffuse attentional window condition, the cue was a large letter, subtending the entire area behind the search display. In the focused attentional window condition, the cue was a small letter presented at the center of the visual display. Figure 1 presents an example of the visual search display used in the present study. Irrelevant to the task, at random intervals a random number of distractor letters changed color (from green to red or vice versa). On average once every 900 ms, the target letter changed color, and it did so alone. This unique target color change was always accompanied by an auditory signal. We expected that this synchronized audiovisual event would capture attention [6]. Importantly, if the size of an attentional window modulates capture by audiovisual events, then we expect better performance when subjects adopt a distributed, more diffuse attentional window than when participants adopt a small, focused attentional window. Moreover, the letter cue was only presented once (300 ms prior to the first target color change, with a duration of 150 ms). Therefore, if setting the attentional window is only effective during a particular time window, one expects that this manipu- lation will affect capture immediately following the attentional window manipulation (i.e., the first synchronized audiovisual event) but not so much for audiovisual events later in time. Methods Ethics statement. Written consent was obtained from each participant prior to the experiments. The experiments were approved by the local ethics committee of the Vrije Universiteit. Attentional Window Affects Audiovisual Capture Participants. In Experiment 1, eleven participants (6 female; mean age = 22.3; ranging from 19–27 years) participated. One participant was excluded from further analysis because of an overall high error rate (.15%). In Experiment 2, ten new participants (5 female; mean age = 20.7; ranging from 18–24 years) participated. Participants were paid J7 an hour. Stimuli and apparatus. Experiments were run in a dimly lit, air-conditioned cabin. Participants were seated approximately 80 cm from the monitor and wore Sennheiser HD 202 headphones. The auditory stimulus was a 500 Hz tone (44.1 kHz sample rate; 16 bit; mono) with a duration of 60 ms (including a 5 ms fade-in and fade-out to avoid clicks) presented on the headphones. The visual search displays consisted of 24 or 48 red (13.9 cd m22) or green (46.4 cd m22) capital letters (Font type: ‘‘Arial’’; height 0.7u; width 0.6u) from the alphabet on a black (,0.05 cd m22) background. Color of each letter was randomly determined. All letters were placed on three imaginary circles with a radius of 3.0u, 4.6u, and 6.2u centered around the center of the display, with the constraint that the number of letters for each imaginary circle was limited to 8, 16 and 24 letters, respectively. The distractor letters were randomly determined letters from the alphabet, except the letters S and H which were used as target letters. The display changed continuously at randomly determined intervals of 50, 100, or 150 ms, with the constraint that the target color change was preceded by a 150 ms interval and followed by a 100 ms interval. At the start of each interval, a randomly determined number of distractor letters changed color (from green to red or vice versa), within the following constraint: When set size was 24, the number of letters that changed was 1, 2, or 3. When set size was 48, the number of letters that changed was 1, 4, or 7. Note that the target was not the only visual event that changed alone. Furthermore, the target letter always changed alone and could change on average once every 900 ms (1.1 Hz; minimum = 500 ms; maximum = 1,300 ms). In Experiment 1, the target color change was always accompanied by the auditory signal, and participants were informed about this. In Experiment 2, the tone was always absent. The target letter could not change during the first 5 display changes (on average 500 ms). Note that participants were able to do the task without any color changes (e.g. prior the first target color change) since the target was always present. On each trial, the cue, which was another letter S or H was presented. The first target color change was always preceded by two 150 ms intervals. The cue was presented during the first 150 ms interval (which is equivalent to 300 ms before the target color change). The cue was briefly presented (for 150 ms) to make sure that participants immediately processed the cue. The cue was light grey either small (width 0.4u; height 0.4u) or large (width 13.0u; height 13.0u) and presented at the center of the display for a fixed duration of 150 ms. Design and procedure. The set size was either 24 or 48. The other manipulation involved the size of the cue (small or large). Participants were asked to memorize the cue, as this was necessarily to make a correct response to the target letter. Dependent variables were the reaction time (RT) and accuracy. Note that the RT reflects the time to respond from the first target letter color change. Each trial began with the presenta- tion of a fixation dot for 500 ms at the center of the screen, followed by a 500 ms blank screen. Subsequently, the search display appeared until participants responded. Participants were instructed to press the z-key when the target letter was identical to the cue, or to press the/2key when it was not identical to the cue. The S and H were balanced for cue and target letter and randomly mixed within blocks of 24 trials each. In Experiment 1, participants received eight large-cue blocks and PLoS ONE | www.plosone.org 2 July 2012 | Volume 7 | Issue 7 | e39137