Performance of Korean-English bilinguals on an adaptation of the screening bilingual aphasia test

The use of standardized tests specifically designed for and normed on bilingual groups is crucial for the accurate diagnosis and language profiling of bilingual speakers with aphasia. Currently, there is a dearth of norms and supporting psychometric data for the few available bilingual aphasia assessments. The only available aphasia test for Korean-English (KE) bilinguals is the Korean-English Bilingual Aphasia Test (KE-BAT). The absence of bilingual normative data for the KE-BAT limits its clinical and research utility.

(1) To revise the original screening KE-BAT to clarify ambiguities in its instructions and stimuli; and (2) to examine subtest and item performance across the two languages for the revised screening KE-BAT with a local sample of highly proficient KE bilinguals.

The original screening KE-BAT was first revised to replace unrecognizable drawings, address ambiguities in the instructions and stimuli, and increase the number of items on naming subtests. This revised test is henceforth referred to as the adapted screening KE-BAT (AS KE-BAT). A total of 21 neurologically healthy, highly proficient and college-educated KE bilinguals (19-34 years old) were recruited from a large city in the United States. Participants completed three measures of language proficiency and the AS KE-BAT including the KE translation test (Part C). Total and subtest scores were compared across the two languages, and individual item accuracy was calculated. Incorrect responses of low scoring items were examined.

Performance was comparable across Korean and English for all subtests, except for the spontaneous speech subtest. The item accuracy of 17 items (7% of total items) in the AS KE-BAT fell to < 80%, and four items (1.6% of total items) had an accuracy < 60%. Incorrect responses of low scoring items were caused by phoneme misperception, lexical substitution and morphosyntactic L2 patterns.

The results of the study highlight the importance of empirically examining the performance of neurotypical bilinguals on bilingual aphasia assessments to establish their psychometric properties. Based on the small-sized local bilingual normative sample obtained in this study, appropriate cut-off criteria, recommendations for clinical interpretation and further modifications of the AS KE-BAT are proposed.

What is already known on the subject The pair of English and Korean aphasia assessments (e.g., Western Aphasia Battery-Revised; WAB-R) (Kertesz 2012) and Korean Western Aphasia Battery (Kim and Na 2001) cannot be used to assess language impairments in KE bilinguals with aphasia since these tests have not been designed for and normed on the bilingual group. Clinical utility of the Korean-English Bilingual Aphasia Test (KE-BAT), which is the only resource currently available to assess KE bilinguals with aphasia, is greatly compromised by the lack of KE bilingual normative data. What this study adds to existing knowledge This study provides cut-off scores, comparability of test performance and item difficulty metrics and it identifies additional ways in which items and spontaneous speech scoring of the adapted screening KE-BAT (AS KE-BAT) could be modified. Suggested guidelines allow improved interpretations of the linguistic performance of local KE bilinguals with aphasia who have a similar demographic and linguistic background. What are the potential or actual clinical implications of this work? The AS KE-BAT with cut-off criteria of 95% for Part B and 80% for Part C is suitable for the language assessment of highly proficient and young KE bilinguals with a high level of education and it yields comparable performance across the two languages. Clinicians may decide to adjust spontaneous speech scoring criteria if the client's language history is suggestive of code-switching and use the item difficulty data to guide test item selection for this group of bilinguals.