Lexical tone representations in Chinese – Evidence from a patient with tone errors but preserved onsets and rhymes

Background. Chinese is a tonal language, in which syllables of different lexical tones refer to different morphemes. One frequently asked theoretical question regarding tonal language concerns the nature of mental representations of syllables in the lexicon - E.g. Are lexical items stored as tonal syllables or are they stored as non-tonal syllables which undergo separate tonal processing in the lexical retrieval process. In the current study, we report a case study conducted using the cognitive neuropsychological approach to address this question.
Methods. TOT, a stroke survivor at the age of 56 years who speaks Cantonese (a dialect of Chinese used in Hong Kong) primarily, reported to have tone production problem after stroke was recruited. TOT's premorbid normal tone production was confirmed using audio recordings obtained from her WhatsApp conversation history during the assessment session. Initial assessment using the Cantonese Aphasia Battery (Yiu, 1994) indicated TOT suffered from conduction aphasia (AQ score = 61.8). TOT was further assessed using various production and identification tasks.
Results. In the passage reading and picture naming tasks, TOT demonstrated lots of tonal errors (where the onsets and rhymes of target words are correctly produced but tones are incorrectly produced). In a written homophone judgement task, TOT was instructed to select from six characters (including the target, an orthographic distractor, a semantic distractor and three phonological distractors differ from the target by only onset, rhyme or tone correspondingly) the one that is homophonous to a presented character. She made 28 errors in all 100 trials. Results of Chi square test indicated that among all the errors, she showed a significantly higher tendency (p < .05) of selecting tonal distractors.
Discussion. TOT’s tone errors with preserved onset and rhyme representations in both production and identification suggested that onsets and rhymes are probably represented independent of tone in Chinese.