Volume 135, Issue 2, February 2014
Index of content:
- SPEECH PERCEPTION 
135(2014); http://dx.doi.org/10.1121/1.4861921View Description Hide Description
This paper examines the perceptual weight of cues to the coda glottal consonant contrast in Trique (Oto-Manguean) with native listeners. The language contrasts words with no coda (/Vː/) from words with a coda glottal stop (/VɁ/) or breathy coda (/Vɦ/). The results from a speeded AX (same–different) lexical discrimination task show high accuracy in lexical identification for the /Vː/-/Vɦ/ contrast, but lower accuracy for the other contrasts. The second experiment consists of a labeling task where the three acoustic dimensions that distinguished the glottal consonant codas in production [duration, the amplitude difference between the first two harmonics (H1-H2), and F0] were modified orthogonally using step-wise resynthesis. This task determines the relative weight of each dimension in phonological categorization. The results show that duration was the strongest cue. Listeners were only sensitive to changes in H1-H2 for the /Vː/-/Vɦ/ and /Vː/-/VɁ/ contrasts when duration was ambiguous. Listeners were only sensitive to changes in F0 for the /Vː/-/Vɦ/ contrast when both duration and H1-H2 were ambiguous. The perceptual cue weighting for each contrast closely matches existing production data [DiCanio (2012 a). J. Phon. 40, 162–176] Cue weight differences in speech perception are explained by differences in step-interval size and the notion of adaptive plasticity [Francis et al. (2008). J. Acoust. Soc. Am. 124, 1234–1251; Holt and Lotto (2006). J. Acoust. Soc. Am. 119, 3059–3071].
135(2014); http://dx.doi.org/10.1121/1.4861350View Description Hide Description
The present study investigated the ability of native listeners to identify subtle phonetic contrasts in nonsense words and its relationship with the contralateral inhibition of transient evoked otoacoustic emissions (TEOAE). A group of 45 young adults with normal hearing sensitivity who were native speakers of Malayalam participated in the behavioral experiment. Phone identification score and reaction time for four phonetic pairs in nonsense words were measured for each participant. Based on the phone identification score, the participants were divided into high and low performers. Twelve participants randomly selected from each group were evaluated for contralateral inhibition of TEOAEs. Phone identification score and global contralateral inhibition amplitude of TEOAE were significantly higher and reaction time was significantly shorter in high performers than that of low performers. Significant correlation was found between the phone identification score and contralateral inhibition of TEOAE. Strength of the medial olivocochlear bundle activity explained about 30% of the variance in the phone identification scores providing evidence for the involvement of the descending auditory pathways in identifying the phonetic contrasts that are acoustically similar. These results support the emerging view that top down influences from higher centers shapes the responses of lower centers.