Abstract
While visual information from facial speech modulates auditory speech perception, it is less influential on audiovisual speech perception among autistic individuals than among typically developed individuals. In this study, we investigated the relationship between autistic traits (Autism-Spectrum Quotient; AQ) and the influence of visual speech on the recognition of Rubin's vase-type speech stimuli with degraded facial speech information. Participants were 31 university students (13 males and 18 females; mean age: 19.2, SD: 1.13 years) who reported normal (or corrected-to-normal) hearing and vision. All participants completed three speech recognition tasks (visual, auditory, and audiovisual stimuli) and the AQ-Japanese version. The results showed that accuracies of speech recognition for visual (i.e., lip-reading) and auditory stimuli were not significantly related to participants' AQ. In contrast, audiovisual speech perception was less susceptible to facial speech perception among individuals with high rather than low autistic traits. The weaker influence of visual information on audiovisual speech perception in autism spectrum disorder (ASD) was robust regardless of the clarity of the visual information, suggesting a difficulty in the process of audiovisual integration rather than in the visual processing of facial speech.
Highlights
The results demonstrated that the McGurk effect was weaker in individuals with high Autism-Spectrum Quotient (AQ) scores than in those with low AQ scores, even when distorted structural facial information was used in McGurk stimuli (Ujiie et al, 2015, 2018)
AQ was significantly and positively correlated with audio (‘apa’) responses in the McGurk condition [r = 0.36, p = 0.049, 95% confidence interval (CI) = 0.01–0.63, Bayes factor (BF10) = 1.42], while the correlation was not significant in the audiovisual congruent condition (r = −0.09, p = 0.648, 95% CI = −0.43–0.28, BF10 = 0.25)
There was no significant correlation of AQ with correct responses in the auditory (r = −0.10, p = 0.581, 95% CI = −0.44–0.26, BF10 = 0.26) nor in the visual condition (r = −0.04, p = 0.837, 95% CI = −0.39–0 .32, BF10 = 0.23)
Summary
The interaction of voice and facial speech can be seen in a well-known illusion, the McGurk effect (McGurk and MacDonald, 1976), in which a facial speech cue (/ka/) dubbed with an incongruent voice (/pa/) is presented, and most observers will perceive an intermediate phoneme (/ta/) even if they are instructed to ignore the facial speech cue. In this process, contradictory phonetic and visual information is loaded simultaneously and processed interactively through an integration process, which results in a fused percept (e.g., Beauchamp et al, 2004; Calvert et al, 2000). Some studies have shown that the McGurk effect decreases if structural facial information is distorted: a reduced McGurk effect was demonstrated with inverted face stimuli (Jordan and Bevan, 1997; Ujiie et al, 2018) and Thatcher-illusion face stimuli (Eskelund et al, 2015; Rosenblum et al, 2000; Ujiie et al, 2018)
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