New patterns of pathological language mixing in bilingual aphasia.

Background: A central challenge in bilingual aphasia research is the absence of clear markers that distinguish pathological language mixing (PLM) from mixing used as a compensatory mechanism, leaving ongoing debates unresolved. Also, prior work suggests that PLM occurs primarily during retrieval of open-class words and increases with utterance length during structured tasks, yet these findings, and the hesitation behaviors accompanying PLM, remain largely untested in spontaneous speech. Method: This study examines PLM in Patient P3, a 59-year-old female bilingual speaker of Spanish and English with severe Broca's aphasia who showed extensive mixing and reported significant communicative disruption as a result. She was administered the Western Aphasia Battery-Revised in both languages and transcribed samples from her response to narrative prompts were coded for word class and language mixing, and hesitation durations were acoustically analyzed. Results: P3 mixed closed-class words more frequently than open-class words. PLM frequency was unrelated to utterance length, and longer hesitations preceded non-target language intrusions, indicating increased retrieval cost. P3 showed elevated Aphasia Quotients in both languages when cross-language responses were computed, suggesting symmetric (bidirectional) mixing rather than assymetric (unidirectional) compensatory intrusion into the weaker language. Conclusion: Together, these results propose symmetric language mixing and higher hesitation duration preceding non-target intrusions as potential markers of control deficits in bilingual aphasia.