Factors affecting cross-language activation and language mixing in bilingual aphasia: A case study

Background Some bilinguals with aphasia tend to mix languages within a single utterance. Two opposing views attribute this to difficulty with either language control or word retrieval. Aims This study investigated the influence of factors that increase activation of the non-target language on the occurrence of language mixing errors. This increased activation predicts more language mixing errors if there is a language control issue, but not if they stem from word retrieval difficulties. Methods and procedures A picture naming experiment was conducted with a bilingual individual with aphasia who showed language mixing. We investigated the influence of four factors likely to influence activation of representations of the non-target language on response accuracy, response latency and the occurrence of language selection errors: language, language mode, task, and phonological overlap between the target word and its translation equivalent. Outcomes and results The increased activation of the non-target language induced by language mode, task and phonological overlap with the translation equivalent did not lead to an increase in language selection errors when compared to correct responses. This is despite the fact that these factors affected accuracy and response latency, in the direction that is expected in unimpaired bilingual performance. Conclusions Results were not consistent with a disruption of the cognitive control needed to respond in the intended language. Instead, they highlight that language mixing in this individual, rather than being "pathological", is instead used as a strategy to potentially improve communication when lexical retrieval difficulties occur. Language mixing behaviours in aphasia may not be due to issues of control and have a communicative value that should be recognised.