Temporal Coherence in Crossmodal Perceptual Binding: Implications for the Design of a Real-Time Multisensory Speech Recognition Algorithm

The inputs delivered to different sensory organs provide complementary information about the environment. Many previous studies have demonstrated that presenting multisensory information (e.g., visual) can improve auditory perception, especially in noisy environments. Understanding temporal asynchronicity between different sensory modalities is fundamentally important to process and deliver multisensory information in real time with minimal time delay. The purpose of this study was to quantify the average limit of temporal asynchronicity where multisensory stimuli are likely to be perceptually integrated. Twenty adults participated in simultaneity judgment measurements using 100-ms stimuli in three different sensory modalities (auditory, visual, and tactile), and their test-retest reliability of the simultaneity judgments was verified on a weekly basis by three separate tests. Two crossmodal temporal coherence cues were examined: the temporal binding window (TBW), denoting a time frame where two sensory modalities were perceptually integrated, and the point of subjective simultaneity (PSS), denoting a perceptual lead toward one modality over others. According to the average results, the TBWs occurred in 389 ms (auditory-visual, AV), 324 ms (auditory-tactile, AT), and 299 ms (visual-tactile, VT), and the PSSs were shifted 105 ms toward a visual cue, 16 ms toward a tactile cue, and 77 ms toward a visual cue for the AV, AT, and VT conditions, respectively. Over all three crossmodalities, the test-retest reliability averaged less than 50 ms for the TBW and 30 ms for the PSS. The findings in this study might specify a minimum amount of time delay for real-time multisensory processing, suggesting temporal parameters for future developments in multisensory hearing assistive devices.