Auditory and visual distractors disrupt multisensory temporal acuity in the crossmodal temporal order judgment task.

The ability to synthesize information across multiple senses is known as multisensory integration and is essential to our understanding of the world around us. Sensory stimuli that occur close in time are likely to be integrated, and the accuracy of this integration is dependent on our ability to precisely discriminate the relative timing of unisensory stimuli (crossmodal temporal acuity). Previous research has shown that multisensory integration is modulated by both bottom-up stimulus features, such as the temporal structure of unisensory stimuli, and top-down processes such as attention. However, it is currently uncertain how attention alters crossmodal temporal acuity. The present study investigated whether increasing attentional load would decrease crossmodal temporal acuity by utilizing a dual-task paradigm. In this study, participants were asked to judge the temporal order of a flash and beep presented at various temporal offsets (crossmodal temporal order judgment (CTOJ) task) while also directing their attention to a secondary distractor task in which they detected a target stimulus within a stream visual or auditory distractors. We found decreased performance on the CTOJ task as well as increases in both the positive and negative just noticeable difference with increasing load for both the auditory and visual distractor tasks. This strongly suggests that attention promotes greater crossmodal temporal acuity and that reducing the attentional capacity to process multisensory stimuli results in detriments to multisensory temporal processing. Our study is the first to demonstrate changes in multisensory temporal processing with decreased attentional capacity using a dual task paradigm and has strong implications for developmental disorders such as autism spectrum disorders and developmental dyslexia which are associated with alterations in both multisensory temporal processing and attention.