汉语语音范畴性知觉及其发展

Categorical Perception of VOT and Lexical Tones in Chinese and the Developmental Course

范畴性是言语知觉的一个显著特征,长期以来一直受到研究者的普遍关注。但汉语不同语音特征的范畴性知觉特点及其发展模式迄今为止还很少有研究涉及。本研究利用语音合成的方法分别改变辅音的送气/不送气特征和声调的基频曲线,生成语音刺激连续体,采用范畴性知觉的经典研究范式探讨了汉语正常成人被试嗓音启动时间(Voice onset time,VOT)和声调范畴性知觉的特点及不同年龄儿童的发展模式。研究结果表明:(1)成人被试对VOT和声调的知觉是范畴性的;(2)对于汉语声调特征,6岁儿童已经具有类似成人的范畴性知觉能力;而在VOT这一维度上,范畴知觉能力随着年龄发展不断精细化,但7岁儿童也尚未达到成年人的敏感程度,说明汉语VOT和声调这两个不同的语音特征经历了不同的发展模式。

Speech perception focuses on the mapping between properties of the acoustic signals and linguistic elements such as phonemes. One of the most important features of speech perception is the phenomenon known as categorical perception （CP） that the continuous sensory inputs are coded categorically. CP has an important influence on the developmental time course of speech perception. Although a large amount of research on CP has been conducted in English and other languages, CP （especially its developmental course） in Chinese has been barely studied. Chinese is a tonal language with some specific phonetic characteristics, such as strong aspiration with long positive voice onset time （VOT） and lexical tones characterized by syllable-level f0 contours. However, the questions such as whether the perception of VOT and lexical tones in Chinese is categorical and how they develop with age are still unaddressed. Using the stimuli of VOT and tone continua created by Klatt, the present two studies investigated CP of VOT and lexical tones in Chinese and their developmental course. Using the classical identification and discrimination paradigm, study 1 investigated the perception of Chinese lexical tone continua and VOT continua in adults. The study was comprised of 4 experiments which included identification and discrimination of VOT and tone respectively. Stimuli were presented to 20 adult subjects in each experiment. The results demonstrated that the perceptions of VOT and lexical tones are both categorical for Chinese adults. Study 2 further investigated the developmental course of Chinese phonetic categorization across lexical tone and VOT continua. The experimental design of this study is a 2 （entity stimuli： VOT, lexical tone） by 4 （age： 5ys, 6ys, 7ys, adults） mixed experiment design. The former was a within-subject factor, while the latter was a between-subject one. Results from Study 2 revealed that six-year-old children already acquired adult-like lexical tone CP competence, but even 7-year-old children were not as good as adults when doing CP of VOT tasks. Therefore, it is proposed that CP of lexical tones is acquired earlier than CP of VOT in Chinese. Further analysis of the correlation between the 2 phonological characteristics showed that they are not correlated with each other. Thus, it is suggested that these two phonetic characteristics are distinct and go through different developmental courses. CP of lexical tone seems to be a phonetic characteristic that is easier to acquire than CP of VOT in Chinese. In conclusion, the findings demonstrated that： （1） the perceptions of both VOT and lexical tones in Chinese are typically categorical for adults; （2） there are different developmental courses for CP of lexical tones and VOT in Chinese. According to the theory proposed by Burnham, we conclude that the Chinese lexical tone is a ＂ robust＂ contrast and is categorically perceived in early childhood; in contrast, VOT is a ＂ fragile＂ contrast that requires more time to develop.