The Influence of Talker Expectations and Acoustic Variability on Speech Perception in ASD

Speech perception is dependent upon the ability to map the sensory features of a speech signal onto the perceptual features which make up language (i.e., phonemes). A great deal of research over the past six decades has focused on how variability across talkers influences speech processing. Listeners are required to normalize the acoustic variability across talkers by continuously updating the mapping from the acoustic signal to phonetic representations. As such, processing speech from multiple talkers is cognitively more demanding than listening to a single talker. This processing cost appears to reflect, in part, the influence of listeners’ expectations that speech is coming from multiple sources (talkers). It remains unclear whether talker normalization effects are present in individuals with autism spectrum disorder (ASD), given broad differences in social and sensory processing. The present study examined talker normalization and effects of talker expectation in adolescents with ASD and typical development. Participants were asked to respond to target words embedded in a stream of speech; the pitch of the talkers (F0) varied in half of trials. Furthermore, half of participants were told that this variability was due to fluctuations in a single talker’s speech, while the other half were told that the speech was variable because it was produced by two talkers. Results indicated that participants with ASD were significantly slower to respond under conditions of acoustic variability, while typically developing participants were not. Furthermore, the degree to which participants with ASD were influenced by the variability was significantly correlated with parent-reported sensory atypicality. This relationship was not moderated by ASD symptom severity. Neither diagnostic group was influenced by the manipulation of expectations. Overall, these results suggest that sensory differences present in ASD may account in part for communication difficulties