 Marian's research revealed that bilinguals activate both languages in parallel during spoken language comprehension.The traditional account of bilingual spoken language processing was the Language Switch Hypothesis, which posited that bilinguals turn off the non-target language during target language processing.Using eye-tracking, Marian demonstrated that bilinguals do not turn off the non-target language, and instead process the two languages in parallel and co-activate words from both languages as speech unfolds.