Abstract
In unisensory contexts, spatially-focused attention tends to enhance perceptual processing. How attention influences the processing of multisensory stimuli, however, has been of much debate. In some cases, attention has been shown to be important for processes related to the integration of audio-visual stimuli, but in other cases such processes have been reported to occur independently of attention. To address these conflicting results, we performed three experiments to examine how attention interacts with a key facet of multisensory processing: the temporal window of integration (TWI). The first two experiments used a novel cued-spatial-attention version of the bounce/stream illusion, wherein two moving visual stimuli with intersecting paths tend to be perceived as bouncing off rather than streaming through each other when a brief sound occurs near in time. When the task was to report whether the visual stimuli appeared to bounce or stream, attention served to narrow this measure of the TWI and bias perception toward “streaming”. When the participants’ task was to explicitly judge the simultaneity of the sound with the intersection of the moving visual stimuli, however, the results were quite different. Specifically, attention served to mainly widen the TWI, increasing the likelihood of simultaneity perception, while also substantially increasing the simultaneity judgment accuracy when the stimuli were actually physically simultaneous. Finally, in Experiment 3, where the task was to judge the simultaneity of a simple, temporally discrete, flashed visual stimulus and the same brief tone pip, attention had no effect on the measured TWI. These results highlight the flexibility of attention in enhancing multisensory perception and show that the effects of attention on multisensory processing are highly dependent on the task demands and observer goals.
Highlights
The selective focusing of attention on a particular region in space provides a more accurate representation of the objects that lie within that region than those that lie within unattended regions
Whereas in Experiment 1 the measure for integration (a ‘‘bounce’’ perception) was more likely to occur at the unattended location, at least as the multisensory components were more separated in time, here the measure for integration was less likely to occur at the unattended location, when the audio and visual events were closer in time even physically simultaneous and would have been expected to be temporally integrated
Having attention directed away from the uncued side may have increased the uncertainty of the timing of both the visual intersection and that of the auditory stimulus, while increasing the complexity of the task, which may have resulted in the shift in criterion that we see here
Summary
The selective focusing of attention on a particular region in space provides a more accurate representation of the objects that lie within that region than those that lie within unattended regions. With accurate perception being crucial to optimal behavioral responses, the topic of the role that attention plays in enhancing perception has been studied for decades (see Carrasco, 2011 for review). One method that has been used to characterize how attention is focused and Attention and multisensory temporal integration the ramifications of that focus is attentional cueing (Posner, 1980). In spatial cueing studies of visual attention, participants are cued to shift their attention to a particular location, while ignoring other locations, in preparation for an upcoming stimulus that is likely to occur in the cued location (e.g., Posner, 1980; Posner and Cohen, 1984; Weichselgartner and Sperling, 1987; Müller and Rabbitt, 1989; Berger et al, 2005; Giordano et al, 2009). Data from neural studies of the allocation of spatial attention suggest that this improvement in behavioral performance is the result of a gain in the event-related response of the sensory cortices responsible for processing the targets, as well as surrounding inhibition of the processing of the distractors (Motter, 1993; Luck et al, 1994, 1997; Mangun, 1995; Hopf et al, 2006; Silver et al, 2007)
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