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Visual-tactile integration and individual differences in speech perception Bicevskis, Katie

Abstract

Integration of speech information is evident in audio-visual (McGurk & MacDonald, 1976) and audio-tactile (Gick & Derrick, 2009) combinations and an asymmetric window of multimodal integration exists which is consistent with the relative speeds of the various signals (Munhall et al., 1996; Gick et al., 2010). It is presently unclear whether integration is possible if the audio speech signal is removed. The current thesis utilizes synchronous and asynchronous visual and aero-tactile speech stimuli to investigate potential integration effects of this modality combination and explores the shape of the potential window of visual-tactile integration. Results demonstrate that the aero-tactile stimulus significantly affects categorization of speech segments so that individuals are more likely to perceive a voiceless aspirated stop when they experience a combination of visual-tactile stimuli, as opposed to experiencing a visual stimulus in isolation. A window of visual-tactile integration which reflects relative speeds of light and speech airflow is also evident. These results add to our knowledge of multimodal speech integration and support notions that speech is perceived as a holistic, modality neutral event. Children with Autism Spectrum Disorder (ASD) have exhibited differential multimodal integration behaviour (Gelder et al., 1991; Mongillo, et al., 2008; Irwin et al., 2011; Stevenson, et al., 2014) and differences in temporal acuity (Stevenson, et al., 2014) as compared to typically developing children, however it is unclear whether these differential findings are specific to this clinical population or can be considered part of a continuum of multimodal integration behaviour which includes typically developed adults. The current thesis examines individual differences in visual-tactile integration based on temporal acuity and behavioural traits associated with ASD, in a typically developed adult population. Results show that temporal acuity and behavioural traits associated with ASD, especially the trait of imagination, significantly influence the range of asynchronous stimuli over which visual-tactile integration occurs and also affect individuals’ abilities to differentiate visually similar speech stimuli. These results reveal a relationship between visual-tactile integration rates, traits associated with ASD and temporal acuity and suggest that the differential behaviour observed in child ASD populations forms part of a continuum which extends to typically developed adults.

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Attribution-NonCommercial-NoDerivs 2.5 Canada

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