Wong Puisan, Strange Winifred
Division of Speech and Hearing Sciences, Faculty of Education, The University of Hong Kong, Pokfulam, Hong Kong.
Ph.D. Program in Speech-Language-Hearing Sciences, The Graduate School and University Center of the City University of New York, New York, New York, United States of America.
PLoS One. 2017 Aug 14;12(8):e0182337. doi: 10.1371/journal.pone.0182337. eCollection 2017.
This is the first study to examine the effect of phonetic contexts on children's lexical tone production. Mandarin tones in disyllabic words produced by forty-four 2- to 6-year-old children and twelve mothers were low-pass filtered to eliminate lexical information. Native Mandarin-speaking adults categorized the tones based on the pitch information in the filtered stimuli. All mothers' tones were categorized with ceiling accuracy. Counter to the findings in most previous studies on children's tone acquisition and the prevailing assumption in models of speech development that children acquire suprasegmental features much earlier than segmental features, this study found that children as old as six years of age have not mastered the production of Mandarin tones. Children's tones were judged with significantly lower accuracy than mothers' productions. Tone accuracy improved, while cross subject variability in tone accuracy decreased, with age. Children's tone accuracy was affected by the articulatory complexity of phonetic contexts. Children made more errors in tone combinations with more complex fundamental frequency (F0) contours than tone sequences with simpler F0 changes. When producing disyllabic tone sequences with complex F0 contours, children tended to shift the F0 contour of the first tone to reduce the F0 change, resulting in more tone errors in the first syllable than in the second syllable and showing substantially more anticipatory coarticulation than adults. The results provide further evidence that acquisition of lexical tones is a protracted process in children. Tones produced accurately by children in one phonetic context may not be produced correctly in another phonetic context. Children demonstrate more anticipatory coarticulation in their disyllabic productions than adults, which may be attributed to children's immature speech motor control in tone production, and is presumably a by-product of their inability to accomplish complex F0 changes within the syllable time-frame.
这是第一项研究语音语境对儿童词汇声调产出影响的研究。对44名2至6岁儿童和12名母亲说出的双音节词中的普通话声调进行低通滤波，以消除词汇信息。以普通话为母语的成年人根据滤波后刺激中的音高信息对声调进行分类。所有母亲的声调分类准确率均达到上限。与以往大多数关于儿童声调习得的研究结果以及语音发展模型中普遍认为儿童比音段特征更早习得超音段特征的假设相反，本研究发现，6岁的儿童尚未掌握普通话声调的产出。儿童声调的分类准确率显著低于母亲的产出。声调准确率随着年龄的增长而提高，同时声调准确率的个体间差异减小。儿童的声调准确率受语音语境发音复杂性的影响。与具有较简单基频（F0）变化的声调序列相比，儿童在具有更复杂F0轮廓的声调组合中犯的错误更多。在产出具有复杂F0轮廓的双音节声调序列时，儿童倾向于改变第一个声调的F0轮廓以减少F0变化，导致第一个音节的声调错误比第二个音节更多，并且比成年人表现出更多的预期协同发音。这些结果进一步证明，儿童习得词汇声调是一个漫长的过程。儿童在一种语音语境中准确产出的声调，在另一种语音语境中可能无法正确产出。儿童在双音节产出中比成年人表现出更多的预期协同发音，这可能归因于儿童在声调产出中不成熟的言语运动控制，大概是他们无法在音节时间框架内完成复杂F0变化的副产品。
