Attentional Window Affects Audiovisual Capture Figure 4. Correct mean reaction time (RT) as a function of set size and cue size. doi:10.1371/journal.pone.0039137.g004 However, if the large cue was somehow beneficial in relation to eye movements, one would expect a similar benefit in Experiment 2, which was not the case. One might state that the actual attentional window effects were not observed, because the relatively small RT effect (of about 250 ms in Experiment 1) may have been obscured by the relative large search times in Experiment 2. Therefore, we conducted the same analysis as in Experiment 1 for the proportion of responses in which participants responded faster than 1,200 ms. Figure 5 presents the proportion of responses as a function cue size, and eccentricity (collapsed over set size). There was a reliable eccentricity effect, F(2, 18) = 20.1, p,.001, as the proportion responses decreased as the target appeared further from fixation. There was no effect of cue size, F(1, 9) = 3.7, p = .085. Neither was there a significant Cue size 6 Eccentricity interaction, F(2, 18) = 2.2, p = .140. As is clear from Figure 5, the cue size had no temporal effect on the presentation of the visual target color change. If anything, the results suggest that participants were better when they were focused than when they were in a diffuse attentional mode, but only when the target appeared close to fixation. If one assumes that search requires serial effortful search (when no tone is present) then it is to be expected that when the focus is narrow people are faster (because one needs to search with a narrow focus) then when it is diffuse (people need to switch from diffuse to focus in order to find the target). A between-experiment analysis was conducted with set size and cue size as within subjects variables. These analyses yielded a reliable effect of experiment, as RTs were faster when the target color change was accompanied by an auditory signal (2,148 ms; Experiment 1) than when no such signal was present (3,465 ms; Figure 5. Proportion of correct responses faster than 1,200 ms after the first audiovisual event, as a function of cue size and eccentricity (distance between fixation and target location). doi:10.1371/journal.pone.0039137.g005 Experiment 2), F(1, 18) = 9.2, p,.01. Furthermore, search slopes were overall shallower in Experiment 1 (35 ms per item) than in Experiment 2 (76 ms per item), as confirmed by a significant Experiment 6 Set size interaction, F(1, 18) = 7.7, p,.01. Thus, search was improved when a visual target was accompanied by a spatially uninformative auditory signal compared to the condition in which no auditory signal was present [6,24]. Important, we observed a reliable Cue size 6 Experiment interaction, F(1, 18) = 6.5, p,.05, indicating a cue size effect in Experiment 1 (i.e. the size of the cue affects capture by audiovisual events), and no cue size effect in Experiment 2. Effect of Time It could well be that the cue size manipulation only had a temporary effect on the guidance by audiovisual integration. For example, a wide cue may initially induce a wide attentional window, but when observers subsequently revert to what is in essence a rather effortful visual search, the attentional focus may narrow down again. To make sure that participants processed the cue immediately, it was presented only briefly (for 150 ms) prior to the first target color change. Thus, the attentional window manipulation may have influenced mainly the first audiovisual events, after which participants returned to their default attentional window. Indeed, Fig. 6 suggests that this was the case. Figure 6 presents the probability of a correct response per target change interval, as a function of cue size, and as a function of tone presence. As is clear from Fig. 6, in the tone present condition, large cues were most effective between the first and the second audiovisual event and gradually decreased with time, indicating PLoS ONE | www.plosone.org 5 July 2012 | Volume 7 | Issue 7 | e39137