语音意识缺陷儿童的言语知觉技能

Considerable studies find that developmental dyslexia is associated with deficits in phonological processing skills, especially phonological awareness. In order to explore the nature of phonological awareness deficits in dyslexia, researchers have begun to investigate the role of speech perception. The findings about speech perception abilities in dyslexics are inconsistent. The heterogeneity of dyslexia may be responsible for the inconsistency of findings. Considering the general suggestion that phonological awareness deficits in dyslexia are attributed to categorical perception deficits, it is more direct to examine whether children with phonological awareness difficulties or phonological dyslexia show speech categorization deficits consistently. The present study would investigate whether Chinese children with phonological awareness deficits or phonological dyslexia showed abnormal speech perception. The whole study consisted of two parts. Part I screened children with phonological-awareness deficits from Year 3 kindergartens and examined their abilities of perceiving native category continuum, nonnative category contrasts and non-speech sound series. Part II selected phonological dyslexics from an elementary school as participants, and further explored the relation between phonological deficits and speech perception. The first two experiments of Part II examined separately the abilities to label stimuli in native category continuum and brief stops in different contexts, the last experiment investigated the adaptation effects of different participant groups. The main conclusions are as follows: 1) Children with phonological dyslexia showed categorical perception deficits: they had lower consistency than controls when perceiving stimuli within phonetic categories, especially for the stimuli which were not natural sounds. 2) Children with phonological dyslexia exhibited a general difficulty of perceiving brief segments of stops from different contexts. 3) Children with phonological dyslexia did not show adaptation to repeatedly presented stimuli. Based on the present conclusions and the findings of previous studies, we suggested that the representations of sound stimuli in phonological dyslexics’ brains are different from those in normal children’s; the representations of sound stimuli in dyslexics’ cortical neural networks are more diffuse and inconsistent.

大量研究证明发展性阅读障碍儿童存在语音意识缺陷。为了探讨阅读障碍及语音意识缺陷的本质，研究者开始关注更基础的言语知觉过程。然而有关阅读障碍儿童或成人言语知觉的研究并没有得出一致的结论。导致研究结果不一致的关键因素是阅读障碍本身存在不同的亚类型，鉴于研究者的一般假设是阅读障碍儿童的语音意识缺陷源于言语知觉问题，因此探讨存在语音意识缺陷或同时存在语音意识缺陷和阅读障碍的儿童是否存在言语知觉异常是更为直接的方式。目前研究以汉语中存在语音意识缺陷或同时存在语音意识缺陷和阅读障碍的儿童为被试，对他们的言语知觉技能进行了考察。 研究包括两部分，研究部分I以幼儿园大班存在语音意识缺陷的儿童为被试，考察了他们识别和分辨汉语语音范畴对比，分辨非母语语音范畴和非言语声音序列的能力。研究部分II以小学中存在阅读障碍/语音意识缺陷的儿童为被试，进一步探讨了语音意识缺陷是否源于言语知觉异常，所采用的测查包括识别母语范畴序列、知觉不同语境中的塞音片段及选择性适应任务。 本研究主要发现如下： 1）语音意识缺陷/阅读障碍儿童存在范畴知觉缺陷，感知范畴内的刺激有更低的一致性，使用合成刺激作实验材料这种缺陷会更加明显。 2）语音意识缺陷/阅读障碍儿童从简短的能量频谱中知觉不同语境中的语音范畴存在困难。 3）语音意识缺陷/阅读障碍儿童对重复呈现的语音刺激缺少适应效应。 结合本研究的结论和以往有关研究的成果，推断语音意识缺陷/阅读障碍儿童表征声音刺激的方式可能与正常儿童存在根本差异，其声音刺激在大脑皮层神经网络的表征更加扩散、缺少一致性。