Bilingual deep dysphasia

Abstract

We report B.R.B., a bilingual Turkish–English speaker with deep dysphasia. B.R.B. shows the typical pattern of semantic errors in repetition with effects of lexicality and imageability on performance in both languages. The question we asked is whether language type (Turkish or English) or language status—that is, first acquired (L1) or second acquired (L2)—has a greater impact on performance. Results showed that repetition in L1 (Turkish) was better than that in L2 (English). We also observed effects of language status on oral reading, writing to dictation, and naming (spoken and written) with greater impairment to repetition than other tasks in both languages. An additional finding was that spoken-word translation in both directions was worse than written-word translation, and word class had an effect on translation from L1 to L2. We argue that interactive activation models of deep dysphasia could explain deep dysphasia in bilingual speakers and interactions between task and language, if the weighted connections that support language processing in L2 are assumed to be weaker, thus causing rapid phonological decay to have more impact on task performance in L2. Implications of the results for models of bilingual language processing are also considered.

Keywords:

• Aphasia
• Turkish
• Short-term memory

We dedicate this work to B.R.B., who passed away recently.

Notes

1 Turkish is cited as an example of an agglutinating language that approximates to the ideal type (Cromer, 1991). Grammatical function in Turkish is given by adding suffixes to a stem. Separate suffixes on nouns indicate both gender and number, but there is no grammatical gender in Turkish. Nouns are declined in three declensions with six case endings: nominative, genitive, dative, accusative, locative, and ablative; number is marked by a plural suffix. Verbs agree with their subjects in case and number, and, as in nouns, separate identifiable suffixes perform these functions. The order of elements in a verb form is: verb stem + tense aspect marker + subject affix. There is no definite article, although the number “one” may be used as an indefinite article. Subject–object–verb word order in Turkish is typical, but other orders are possible under certain discourse situations. As a subject–object–verb language where objects precede the verb, Turkish has postpositions rather than prepositions and relative clauses that precede the verb. Modern Turkish also has Turkic vowel harmony in which the vowels of suffixes must harmonize with the vowels of noun and verb stems. Thus, for example, if the stem has a round vowel then the vowel of the suffix must be round. Stress assignment on words pronounced in isolation is on the final syllable but stress assignment in discourse can be complicated in the verb (Campbell, 1991; Comrie, 1990).

2  A verbal noun is a noun formed directly as an inflexion of a verb or a verb stem.

3 Within-language semantic errors were observed on all tasks except oral reading in English whereby errors were regularizations (e.g., shoe → “show”). A small number (n = 3) of cross-linguistic errors were given in spoken naming tasks but in L1 only.

4 Note that varying presentation modality in repetition can be done with monolingual speakers, though this is not ideal since repetition of written words (oral reading) may be performed without semantic support in these speakers (Coltheart, Rastle, Perry, Langdon, & Ziegler, 2001).

5 Items were not matched for concreteness, word frequency, or imageability as values are not available in Turkish. Therefore we cannot exclude the possibility that word class effects result from uncontrolled differences in these variables.

6 We note that the two-step model has not yet been tested against monolingual-patient data with tasks using written-word input, and so this question is largely moot.

7 We cannot exclude the possibility that word recognition in English and Turkish was less than perfect, which would allow semantic errors to arise in the first step of the model.

8 The revised hierarchical model of Kroll and Stewart (1994) is a developmental model of second-language acquisition although it has been applied to explaining translation performance. We assumed that B.R.B. had developed language skills in English to a proficient level premorbidly. Therefore the model is not relevant to explaining B.R.B.'s normal or impaired performance.

9 Within-language errors are reported in other cases of acquired dyslexia in bilingual speakers (Beaton & Davies, 2007; Weekes, Su, Yin, & Zhang, 2007) and is evidence of language selectivity in oral reading.

10 Cross-linguistic errors during the oral reading of irregular words are not necessary if a lexical reading route for reading in English is damaged but could follow damage to a semantic reading pathway in bilingual speakers (see Raman & Weekes, 2005a).