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Influence of speech rate on auditory neural tracking and neural processing of sentence predictability
Poster Session A - Sandbox Series, Thursday, October 24, 10:00 - 11:30 am, Great Hall 3 and 4
This poster is part of the Sandbox Series.
Minhong Jeong1, Minjeong Kim1, Jieun Song1; 1Korea Advanced Institute of Science and Technology
The act of speaking slowly to the other person reflects the general notion that slower speech would be helpful for the listener, which is indeed supported by previous studies. For instance, older adults with normal hearing could take advantage of additional processing time provided by a slower speaking rate in noisy environments (Adams et al., 2012), or listening effort was reduced for individuals with cochlear implant when speech was slower, partly because they can better utilize contextual information (Winn & Teece, 2021). A recent finding also reported that neural tracking of semantic features increased with decreasing speech rates (Verschueren et al., 2022). However, our recent behavioral study on listening effort with different speech rates, conducted with young normal hearing adults, demonstrated that not only slow speeds were cognitively challenging, but speech comprehension was also impaired at slower rates. As a follow-up, we aim to investigate how neural processing of speech is affected by different speech rates at multiple levels (auditory, lexical-semantic). To this end, we measured electroencephalography responses of normal hearing young adults listening to sentences from Korean Speech Recognition Sentence Corpus (Song et al., 2023) with varying degrees of semantic predictability of the final word (predictable, neutral, anomalous). We time-compressed and expanded sentences of the KSR corpus by 25% each, resulting in three different speed conditions (fast, normal, slow). 10 subjects listened to the stimuli, where they were asked to respond with a key press whenever they heard an incongruent final word in the sentence (i.e., anomalous sentence). Auditory neural tracking of the amplitude envelopes of the sentences was examined using Multivariate Temporal Response Functions (Crosse et al., 2016). The results showed that the degree of neural tracking of the speech envelope increased in the faster condition likely because more acoustic information was processed at an auditory level in a given time (Verschueren et al., 2022). The behavioral results were more unexpected; the accuracy was lower in the slow condition than in the normal rate condition. The N400 response to the final word of each sentence showed that there was a tendency of delayed N400 in the slow condition. A significant interaction was also found between speed and sentence type for N400 amplitudes; they were larger when sentences were presented more slowly compared to the normal speed when subjects were listening to neutral sentences. These preliminary results suggest that speech rate affects both neural and behavioral responses to spoken language, where moderately fast speech like the one used in this study may be facilitating neural efficiency at least at an auditory level, whereas slower speech could be disrupting the natural flow of semantic processing, requiring more cognitive demand. In light of the current findings, we expect to see more elaborated results on whether the brain optimizes the neural mechanisms under higher temporal demands with varying speech rates.
Topic Areas: Speech Perception,