| Summary: | The brain is continuously processing many sources of sensory information. One of the key strategies it uses to determine what stimuli are associated with one another is the temporal delay between multisensory inputs. When stimulus onset asynchronies (SOAs) are sufficiently short, multisensory signals are highly likely to be bound. Extensive research in adults has characterized the temporal structure of audiovisual integration and the alterations in behavior and perception induced by such interactions. However, no prior work has investigated developmental changes in multisensory temporal processing in the period between infancy and adulthood. Here, we present a series of studies detailing maturational changes in the temporal window of audiovisual integration for basic stimuli and speech. Results of our early work revealed age-related differences in 10 and 11 year olds and adults on a nonspeech audiovisual simultaneity judgment task, which suggested that processing alterations persist beyond the first decade of life for basic stimuli. These findings provided the foundation for follow-up studies which sought to characterize the trajectory of multisensory temporal processing maturation from early childhood to early adulthood. To that end, the simultaneity judgment measure previously employed was administered to a group of participants ranging in age from 6 to 23 years. Comparison of responses across subjects indicated that multisensory temporal binding windows were larger in children and adolescents than adults, suggesting that the younger groups were more likely to bind asynchronous audiovisual pairings. To examine whether this developmental effect was generalizable to speech, subjects completed an audiovisual identification task wherein incongruent auditory and visual speech tokens were presented at a range of SOAs. Surprisingly, findings indicated that the temporal binding window for audiovisual speech matures earlier; window sizes were comparable in children, adolescents and adults. Overall, results suggest that the trajectory to realization of adult-like multisensory temporal processing differs for nonspeech and speech stimuli. The role of experience in mediating faster window contraction for speech is speculated upon and the implications of delayed maturation of multisensory processing on overall development are reviewed.
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