Converging Evidence from Bilingualism and Aphasia Reveals a Link
Between Lexical Selection in Comprehension and Production
Bilingualism and aphasia have been traditionally employed as separate platforms for investigating the cognitive mechanisms underlying language production and comprehension. In the present study we take an innovative approach to analyze spoken word recognition as a function of production fluency in second language (L2) learners and individuals with aphasia for a common purpose: to evaluate whether resolving lexical competition during spoken word comprehension engages the same mechanisms as selecting an individual word from a set of candidates for production. We test this hypothesis in a novel way by examining whether narrative speech production fluency is associated with sensitivity to phonological neighborhood density -- a robust measure of resolving lexical competition during speech recognition that is otherwise unrelated to fluent language production. English learners of Spanish (N=24), individuals with aphasia (N=19), age-matched monolingual participants (N=24) and neurologically intact older adults (N=15) identified spoken English words presented in moderate noise. English learners of Spanish varied on measures of L2-Spanish proficiency. Individuals with aphasia varied on measures of fluency and receptive vocabulary, in the absence of comprehension deficits. The words either came from high-density neighborhoods (e.g., BAG) or low-density neighborhoods (e.g., BALL). Age-matched control participants exhibited the standard inhibitory effect of phonological neighborhood density on response times: slower recognition of spoken words from denser neighborhoods. Among English learners of Spanish, this inhibitory effect of phonological neighborhood density was greater for learners with lower L2 fluency. Among participants with aphasia, the inhibitory effect of phonological neighborhood density was similarly greater for participants with lower fluency. Additionally, the neighborhood effect was larger for individuals with aphasia with better receptive vocabulary knowledge, indicating that the fluency effect was not due to general lexical deficits. These converging results from bilingualism and aphasia are consistent with the view that language production and comprehension share a lexical selection mechanism.