Biomedical subjects

Alice Turk

Publications and source records attributed to Alice Turk.

5 recordsLinked to original sources

PubMed2006

Language redundancy predicts syllabic duration and the spectral characteristics of vocalic syllable nuclei.

The language redundancy of a syllable, measured by its predictability given its context and inherent frequency, has been shown to have a strong inverse relationship with syllabic duration. This relationship is predicted by the smooth signal redundancy hypothesis, which proposes that robust communication in a noisy environment can be achieved with an inverse relationship between language redundancy and the predictability given acoustic observations (acoustic redundancy). A general version of the hypothesis predicts similar relationships between the spectral characteristics of speech and language redundancy. However, investigating this claim is hampered by difficulties in measuring the spectral characteristics of speech within large conversational corpora, and difficulties in forming models of acoustic redundancy based on these spectral characteristics. This paper addresses these difficulties by testing the smooth signal redundancy hypothesis with a very high-quality corpus collected for speech synthesis, and presents both durational and spectral data from vowel nuclei on a vowel-by-vowel basis. Results confirm the duration/language redundancy results achieved in previous work, and show a significant relationship between language redundancy factors and the first two formants, although these results vary considerably by vowel. In general, however, vowels show increased centralization with increased language redundancy.

Communication↗

PubMed2005

Spectro-temporal processing during speech perception involves left posterior auditory cortex.

This functional magnetic resonance imaging study investigates the neural underpinnings of spectro-temporal integration during speech perception. Participants performed an auditory discrimination task on a set of sine-wave analogues that could be perceived as either nonspeech or speech. Behavioural results revealed a difference in the processing mode; spectro-temporal integration occurred during speech perception, but not when stimuli were perceived as nonspeech. In terms of neuroimaging, we observed an activation increase in the left posterior primary and secondary auditory cortex, namely Heschl's gyrus and planum temporale encroaching onto the superior temporal sulcus, reflecting a shift from auditory to speech perception. This finding demonstrates that the left posterior superior temporal lobe is essential for spectro-temporal processing during speech perception.

Acoustic Stimulation↗

PubMed2005

The influence of spectral distinctiveness on acoustic cue weighting in children's and adults' speech perception.

Children and adults appear to weight some acoustic cues differently in perceiving certain speech contrasts. One possible explanation for this difference is that children and adults make use of different strategies in the way that they process speech. An alternative explanation is that adult-child cue weighting differences are due to more general sensory (auditory) processing differences between the two groups. It has been proposed that children may be less able to deal with incomplete or insufficient acoustic information than are adults, and thus may require cues that are longer, louder, or more spectrally distinct to identify or discriminate between auditory stimuli. The current study tested this hypothesis by examining adults' and 3- to 7-year-old children's cue weighting for contrasts in which vowel-onset formant transitions varied from spectrally distinct (/no/-/mo/, /do/-/bo/, and /ta/-/da/) to spectrally similar (/ni/-/mi/, /de/-/be/, and /ti/-/di/). Spectrally distinct cues were more likely to yield different consonantal responses than were spectrally similar cues, for all listeners. Furthermore, as predicted by a sensory hypothesis, children were less likely to give different consonantal responses to stimuli distinguished by spectrally similar transitional cues than were adults. However, this pattern of behavior did not hold for all contrasts. Implications for theories of adult-child cue weighting differences are discussed.

Adult↗

PubMed2004

Adult-child differences in acoustic cue weighting are influenced by segmental context: children are not always perceptually biased toward transitions.

It has been proposed that young children may have a perceptual preference for transitional cues [Nittrouer, S. (2002). J. Acoust. Soc. Am. 112, 711-719]. According to this proposal, this preference can manifest itself either as heavier weighting of transitional cues by children than by adults, or as heavier weighting of transitional cues than of other, more static, cues by children. This study tested this hypothesis by examining adults' and children's cue weighting for the contrasts /saI/-/integral of aI/, /de/-/be/, /ta/-/da/, and /ti/-/di/. Children were found to weight transitions more heavily than did adults for the fricative contrast /saI/-/integral aI/, and were found to weight transitional cues more heavily than nontransitional cues for the voice-onset-time contrast /ta/-/da/. However, these two patterns of cue weighting were not found to hold for the contrasts /de/-/be/ and /ti/-/di/. Consistent with several studies in the literature, results suggest that children do not always show a bias towards vowel-formant transitions, but that cue weighting can differ according to segmental context, and possibly the physical distinctiveness of available acoustic cues.

Adult↗

PubMed2004

The smooth signal redundancy hypothesis: a functional explanation for relationships between redundancy, prosodic prominence, and duration in spontaneous speech.

This paper explores two related factors which influence variation in duration, prosodic structure and redundancy in spontaneous speech. We argue that the constraint of producing robust communication while efficiently expending articulatory effort leads to an inverse relationship between language redundancy and duration. The inverse relationship improves communication robustness by spreading information more evenly across the speech signal, yielding a smoother signal redundancy profile. We argue that prosodic prominence is a linguistic means of achieving smooth signal redundancy. Prosodic prominence increases syllable duration and coincides to a large extent with unpredictable sections of speech, and thus leads to a smoother signal redundancy. The results of linear regressions carried out between measures of redundancy, syllable duration and prosodic structure in a large corpus of spontaneous speech confirm: (1) an inverse relationship between language redundancy and duration, and (2) a strong relationship between prosodic prominence and duration. The fact that a large proportion of the variance predicted by language redundancy and prosodic prominence is nonunique suggests that, in English, prosodic prominence structure is the means with which constraints caused by a robust signal requirement are expressed in spontaneous speech.

Communication↗