Department of Speech and Language Therapy, Anadolu University, Eskişehir, Turkey.
Language and Brain Lab, Tel Aviv University, Tel Aviv, Israel.
PLoS One. 2021 Mar 24;16(3):e0249016. doi: 10.1371/journal.pone.0249016. eCollection 2021.
We report on developmental vowel dyslexia, a type of dyslexia that selectively affects the reading aloud of vowel letters. We identified this dyslexia in 55 Turkish-readers aged 9-10, and made an in-depth multiple-case analysis of the reading of 17 participants whose vowel dyslexia was relatively selective. These participants made significantly more vowel errors (vowel substitution, omission, migration, and addition) than age-matched controls, and significantly more errors in vowel letters than in consonants. Vowel harmony, a pivotal property of Turkish phonology, was intact and the majority of their vowel errors yielded harmonic responses. The transparent character of Turkish orthography indicates that vowel dyslexia is not related to ambiguity in vowel conversion. The dyslexia did not result from a deficit in the phonological-output stage, as the participants did not make vowel errors in nonword repetition or in repeating words they had read with a vowel error. The locus of the deficit was not in the orthographic-visual-analyzer either, as their same-different decision on words differing in vowels was intact, and so was their written-word comprehension. They made significantly more errors on nonwords than on words, indicating that their deficit was in vowel processing in the sublexical route. Given that their single-vowels conversion was intact, and that they showed an effect of the number of vowels, we conclude that their deficit is in a vowel-specific buffer in the sublexical route. They did not make vowel errors within suffixes, indicating that suffixes are converted as wholes in a separate sublexical sub-route. These results have theoretical implications for the dual-route model: they indicate that the sublexical route converts vowels and consonants separately, that the sublexical route includes a vowel buffer, and a separate morphological conversion route. The results also indicate that types of dyslexia can be detected in transparent languages given detailed error-analysis and dyslexia-relevant stimuli.
我们报告了一种发展性元音诵读困难，这是一种选择性影响元音字母朗读的诵读困难类型。我们在 55 名 9-10 岁的土耳其语阅读者中发现了这种诵读困难，并对 17 名诵读困难者的阅读进行了深入的多案例分析，他们的元音诵读困难相对较为选择性。这些参与者犯了明显更多的元音错误（元音替代、省略、迁移和添加），比年龄匹配的对照组多，而且在元音字母上的错误比在辅音字母上多。元音和谐，土耳其语音系的关键属性，是完整的，他们的大多数元音错误都产生了和谐的反应。土耳其语正字法的透明性表明，元音诵读困难与元音转换的模糊性无关。诵读困难不是由于语音输出阶段的缺陷造成的，因为参与者在非单词重复或重复他们读过的有元音错误的单词时没有犯元音错误。缺陷的位置也不在拼字-视觉分析器中，因为他们在元音不同的单词的相同-不同判断是完整的，他们的书面词汇理解也是完整的。他们在非单词上犯的错误明显多于单词，这表明他们的缺陷在于子音节路径中的元音处理。鉴于他们的单元音转换是完整的，并且他们表现出元音数量的影响，我们得出结论，他们的缺陷是在子音节路径中的特定于元音的缓冲区中。他们不在后缀中犯元音错误，这表明后缀作为整体在单独的子音节子路径中转换。这些结果对双重路径模型具有理论意义：它们表明子音节路径分别转换元音和辅音，子音节路径包括一个元音缓冲区，以及一个单独的形态转换路径。这些结果还表明，在详细的错误分析和与诵读困难相关的刺激下，透明语言中可以检测到诵读困难的类型。
