年輕與年長者聲調感知之研究

Southern Min Tone Perception by Young and Elderly Adults

陳慈薇(Stacy Szu-wei Chen)

指導教授 ： 麥傑 ； 蔡素娟

國立中正大學/文學院/語言學研究所/博士(2014年)

摘要

本論文主要探討年長與年輕受試者閩南語聲調感知的變化。從聲調的辨識與區辨能力測驗來觀察老化與聽覺敏銳度對聲調感知的影響。過去的文獻指出年長者對輔音的音段特徵的感知(例如：嗓音起始時間)比超音段特徵(例如：音高)的感知有更大的困難。然而，超音段的聽覺線索在聲調語言中所扮演的角色與非聲調語言不同。本研究以說閩南語為母語的受試者為研究對象，受試者分三組：(1)聽力正常(氣導閥值在25 dB HL內)的年輕人，(2)聽力正常的65歲以上老年人，(3)65歲以上有輕微或中度聽力損失(氣導閥值在25~50 dB HL間)的老年人。本論文分為三個實驗：實驗一及實驗三分別研究三組不同受試者對單一不同聲調的辨識和區辨能力；而實驗二則是探討在不同的語音及語意的語境中，老化和聽覺敏銳度對聲調辨識的影響。研究結果顯示聽力正常的年輕受試者在單一聲調辨識及區辨測驗的表現都明顯優於其他兩組年長者，但聽力正常與聽力損失年長者間卻沒有顯著差異。年輕受試者的聲調感知範疇界線也較年長者明顯。雖然語音及語意的語境對三組受試者皆有顯著作用，但語音語境對兩組年長受試者影響較大，而聽損的年長者尤其受語意語境的影響最深。由此推論聽損的年長者更需要語意的線索來彌補聽力損失造成的語言理解困難。本研究結果發現氣導聽覺敏銳度似乎無法正確預測聽者的聲調感知能力，老化相關的因素(例如：聽知覺系統中的時序處理)造成的影響較大。本研究的結論是年長者即使聽覺敏銳度在正常範圍內，他們的聲調感知範疇界線也和年輕者有顯著不同，極有可能年長者在類別感知(categorical perception)的層級上，有感覺登錄(Sensory encoding)的困難。

關鍵字

認知與老化 ； 老化研究 ； 閩南語聲調 ； 聲調感知與處理

並列摘要

This study has examined the effects of age and hearing sensitivity on Southern Min tone perception, from tone discrimination and identification in isolation to tone identification in context. Previous studies have shown that older adults seem to have more problems with segmental features (e.g. VOT) than supra-segmental ones (e.g. stress). However, the role of supra-segmental cues in tone languages is different from that in non-tonal languages. Three groups of participants were recruited: (1) Normal-hearing young participants, (2) Normal-hearing old participants and (3) Old participants with mild or moderate hearing loss. Taiwan Southern Min is the target language of our stimuli.
Experiment 1 first examined the tone identification and discrimination of high-level and mid-level tones by these three groups. In identification task, our results showed that normal-hearing young listeners had a significantly steeper categorical perception slope than the two elderly groups. As for the discrimination data, the normal-hearing young group differed significantly from the other two elderly groups, whereas the two elderly groups were not different from each other. Tests of within-subject effects show that there was no significant main effect of ISI, but a significant main effect of acoustic steps was found: the larger the steps, the easier for all listeners.
Experiment 2 investigated the level tone identification in different acoustic and semantic contexts. In the identification task in context, our data present significant main effects of preceding f0 and semantic contexts. Although all participants were both affected by acoustic and semantic contexts, acoustic contexts seemed to have a greater effect on the normal-hearing old adults. On the other hand, semantic contexts seemed to play a more crucial role than acoustic contexts in the elderly with hearing loss.
Experiment 3 examined the tone identification and discrimination of mid-level tone and low-rising tones in two different durations. The two elderly groups had less problem identifying mid-level tones from low-rising ones in both tone durations. However, both elderly groups could not differentiate two tones as accurately as the younger ones, especially in shorter tone duration trials. Tone duration and acoustic steps both had significant effects on the elderly’s tone perception. Compared with level tone , the contour tone discrimination task seemed to elicit more peaks on the cross-category boundary.
Based on the results of these three experiments, age or age-related variables seem to play a more important role than pure tone threshold in tone perception. Both the normal-hearing elderly and the elderly with hearing loss showed less dichotomous tone boundaries than their younger counterparts. Our findings suggest that the elderly may have impoverished sensory encoding on perceptual categorization level, even without significant peripheral or cognitive deficits.

並列關鍵字

Categorical perception ； Southern Min tone perception ； Tone perception and processing ； Age and hearing sensitivity effects

參考文獻

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