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Bosker, H. R., & Kösem, A. (2017). An entrained rhythm's frequency, not phase, influences temporal sampling of speech. In Proceedings of Interspeech 2017 (pp. 2416-2420). doi:10.21437/Interspeech.2017-73.
AbstractBrain oscillations have been shown to track the slow amplitude fluctuations in speech during comprehension. Moreover, there is evidence that these stimulus-induced cortical rhythms may persist even after the driving stimulus has ceased. However, how exactly this neural entrainment shapes speech perception remains debated. This behavioral study investigated whether and how the frequency and phase of an entrained rhythm would influence the temporal sampling of subsequent speech. In two behavioral experiments, participants were presented with slow and fast isochronous tone sequences, followed by Dutch target words ambiguous between as /ɑs/ “ash” (with a short vowel) and aas /a:s/ “bait” (with a long vowel). Target words were presented at various phases of the entrained rhythm. Both experiments revealed effects of the frequency of the tone sequence on target word perception: fast sequences biased listeners to more long /a:s/ responses. However, no evidence for phase effects could be discerned. These findings show that an entrained rhythm’s frequency, but not phase, influences the temporal sampling of subsequent speech. These outcomes are compatible with theories suggesting that sensory timing is evaluated relative to entrained frequency. Furthermore, they suggest that phase tracking of (syllabic) rhythms by theta oscillations plays a limited role in speech parsing.
Franken, M. K., Eisner, F., Schoffelen, J.-M., Acheson, D. J., Hagoort, P., & McQueen, J. M. (2017). Audiovisual recalibration of vowel categories. In Proceedings of Interspeech 2017 (pp. 655-658). doi:10.21437/Interspeech.2017-122.
AbstractOne of the most daunting tasks of a listener is to map a continuous auditory stream onto known speech sound categories and lexical items. A major issue with this mapping problem is the variability in the acoustic realizations of sound categories, both within and across speakers. Past research has suggested listeners may use visual information (e.g., lipreading) to calibrate these speech categories to the current speaker. Previous studies have focused on audiovisual recalibration of consonant categories. The present study explores whether vowel categorization, which is known to show less sharply defined category boundaries, also benefit from visual cues. Participants were exposed to videos of a speaker pronouncing one out of two vowels, paired with audio that was ambiguous between the two vowels. After exposure, it was found that participants had recalibrated their vowel categories. In addition, individual variability in audiovisual recalibration is discussed. It is suggested that listeners’ category sharpness may be related to the weight they assign to visual information in audiovisual speech perception. Specifically, listeners with less sharp categories assign more weight to visual information during audiovisual speech recognition.