Multisensory Cues Capture Spatial Attention Regardless of Perceptual Load Valerio Santangelo University of Oxford and University of Rome “La Sapienza” Charles Spence University of Oxford We compared the ability of auditory, visual, and audiovisual (bimodal) exogenous cues to capture visuo-spatial attention under conditions of no load versus high perceptual load. Participants had to discriminate the elevation (up vs. down) of visual targets preceded by either unimodal or bimodal cues under conditions of high perceptual load (in which they had to monitor a rapidly presented central stream of visual letters for occasionally presented target digits) or no perceptual load (in which the central stream was replaced by a fixation point). The results of 3 experiments showed that all 3 cues captured visuo-spatial attention in the no-load condition. By contrast, only the bimodal cues captured visuo-spatial attention in the high-load condition, indicating for the first time that multisensory integration can play a key role in disengaging spatial attention from a concurrent perceptually demanding stimulus. Keywords: multisensory integration, audiovisual, attentional capture, exogenous, spatial cuing In the last decade, several studies have attempted to investigate the nature of the interaction between selective attention and per- ceptual load (see Lavie, 2005, for a review). However, the relation between the exogenous orienting of spatial attention and percep- tual load (as well as other kinds of load, such as working memory load; e.g., Santangelo & Spence, 2006) has only recently been examined. This is a particularly important area for research in the context of any assessment of the genuine automaticity of exoge- nous spatial orienting (see Santangelo & Spence, 2007) and one that constitutes the principal aim of the present study. In particular, we wanted to investigate the role that multisensory integration plays in capturing spatial attention as a function of any concurrent increase of perceptual load. Are peripheral onsets capable of reflexively capturing spatial attention when a person’s attentional resources are already en- gaged in another perceptually demanding task? This question was recently addressed by Santangelo, Olivetti Belardinelli, and Spence (2007). They conducted two experiments in which the orienting of spatial attention was measured by means of an orthog- onal spatial cuing task (see Spence, McDonald, & Driver, 2004). The participants were instructed to discriminate as rapidly and accurately as possible the elevation (up vs. down) of a visual target cued shortly beforehand by a spatially nonpredictive peripheral (visual or auditory) stimulus whose location varied on an indepen- dent (i.e., orthogonal) dimension (i.e., left vs. right). Typically, participants’ target discrimination responses in orthogonal spatial cuing studies are faster and more accurate when the elevation discrimination is carried out on the cued as opposed to the uncued side. This result has been taken to indicate the beneficial effect of the shift of spatial attention toward the location in which the cue was presented (see Spence et al., 2004, for a review). In Santangelo et al.’s (2007) study, the spatial orienting of participants’ attention was either measured alone or under condi- tions of concurrent increased perceptual load, provided by the rapid sequential visual (or auditory) presentation (RSV[A]P) of a stream of alphanumeric characters from fixation. The participants in Santangelo et al.’s study had to monitor the RSV(A)P stream in order to detect any digits that might be presented in the stream. In the high perceptual load condition, the participants performed both the orthogonal cuing task and the RSV(A)P task within the same block of experimental trials. By contrast, in the medium-load condition, the participants were only required to perform the orthogonal cuing task, although the RSV(A)P stream was also presented (but no response was required). Finally, in the no-load condition, only the orthogonal cuing task was presented and re- sponded to (i.e., this constituted a baseline condition that did not involve any concurrent increase of perceptual load relative to performing the spatial cuing task by itself). Santangelo et al. argued that if exogenous spatial attentional orienting is influenced by the adoption by participants of a focused attentional state on the central perceptually demanding task, one would expect to find a suppression of cuing effects (i.e., no significant difference between performance on the cued vs. uncued trials) under high- and medium-load conditions. Otherwise, one should expect to find comparable performance (i.e., significant cuing effects) in all three conditions. Santangelo et al. (2007) observed the same pattern of results when they varied both the sensory modality of the intramodal Editor’s Note. Alan Kingstone served as the action editor for this arti- cle.—GWH Valerio Santangelo, Department of Experimental Psychology, Univer- sity of Oxford, Oxford, England, and Department of Psychology, Univer- sity of Rome “La Sapienza,” Rome, Italy; Charles Spence, Department of Experimental Psychology, University of Oxford. This study was supported by a postdoctoral research grant awarded to Valerio Santangelo by the Faculty of Psychology, University of Rome “La Sapienza.” Correspondence concerning this article should be addressed to Valerio Santangelo, Department of Psychology, University of Rome “La Sapienza,” via dei Marsi 78, 00185, Roma, Italy. E-mail: valerio.santangelo@uniroma1.it Journal of Experimental Psychology: Copyright 2007 by the American Psychological Association Human Perception and Performance 2007, Vol. 33, No. 6, 1311–1321 0096-1523/07/$12.00 DOI: 10.1037/0096-1523.33.6.1311 1311