Involuntary orienting to sound improves visual perception

To perceive real-world objects and events, we need to integrate several sti mulus features belonging to different sensory modalities. Although the neur al mechanisms and behavioural consequences of intersensory integration have been extensively studied(1-4), the processes that enable us to pay attenti on to multimodal objects are still poorly understood. An important question is whether a stimulus in one sensory modality automatically attracts atten tion to spatially coincident stimuli that appear subsequently in other moda lities, thereby enhancing their perceptual salience. The occurrence of an i rrelevant sound does facilitate motor responses to a subsequent light appea ring nearby(5-7). However, because participants in previous studies made sp eeded responses rather than psychophysical judgements, it remains unclear w hether involuntary auditory attention actually affects the perceptibility o f visual stimuli as opposed to postperceptual decision and response process es. Here we provide psychophysical evidence that a sudden sound improves th e detectability of a subsequent flash appearing at the same location. These data show that the involuntary orienting of attention to sound enhances ea rly perceptual processing of visual stimuli.