Non-treated languages in aphasia therapy of polyglots benefit from improvement in the treated language

The present case study aims to investigate whether the treatment of a third language (L3 French) in a trilingual chronic Wernicke-aphasic patient leads to the parallel improvement of the first (L1 German) and second (L2 English) languages. After a linguistic assessment in each language by means of the Bilingual Aphasia Test (BAT) [Paradis, M. (1987). The assessment of bilingual aphasia. Hillsdale: Lawrence Erlbaum], the patient was intensively treated in his L3 twice a day for 45 min for three and a half weeks. The treatment focussed on lexical–semantic deficits. Subsequent to the treatment, the patient was tested again in the three languages. The resulting recovery pattern shows that both L2 and L3 significantly improved after treatment with a larger effect for the treated language (L3) than for the L2. In contrast, L1 (German) did not show significant improvement, probably because the test results were already above-average for the first testing (T1). The present findings lend support to cognitive models of bilingual word recognition postulating that a bilingual's two languages share a common semantic–conceptual memory system.