Word recognition in early bilingual adults for two degradation types

Abstract

Early bilingual adults have difficulty perceiving speech in noise compared to monolingual adults; however, the cause of the deficit is unknown. Further, the extent to which this deficit extends to other types of degradation, such as source degradation (e.g., a nonnative accent) has not been investigated. The current study investigated word recognition under environmental and source degradation by 24 monolingual and 24 bilingual listeners, who learned English and at least one other language before age 6. Participants identified sentences produced by one native and one nonnative talker in both quiet and noise-added conditions. Although noise was more detrimental to bilinguals than monolinguals, the presence of a nonnative accent caused a similar decline for both groups. Results from standardized tests of vocabulary, reading, spelling, nonverbal intelligence, and phonological processing showed two differences between the groups: bilinguals outperformed monolinguals on the nonverbal intelligence test (Raven’s Standard Progressive Matrices) and bilinguals performed less accurately than monolinguals on the vocabulary assessment (Peabody Picture Vocabulary Test). Therefore, the speech-in-noise deficit for bilinguals may be traced to their weaker vocabulary knowledge. This study demonstrates that early bilinguals experience a word-recognition disadvantage under environmental degradation but not source degradation.