Lost in Translation Speech recognition and memory processes in native and non-native language perception

Sammanfattning: This thesis employed an integrated approach and investigated intra- and inter-individual differences relevant for normally hearing (NH) and hearing-impaired (HI) adults in native (Swedish) and non-native (English) languages in adverse listening conditions. The integrated approach encompassed the role of cognition as a focal point of interest as well as perceptualauditory and linguistic factors. Paper I examined the extent to which proficiency in a non-native language influenced native and non-native speech perception performance for NH listeners in noise maskers compared to native and non-native speech maskers. Working memory capacity in native and non-native languages and non-verbal intelligence were also assessed. The design of paper II was identical to that of paper I, however the participants in paper II had a hearingimpairment. The purpose of paper III was to assess how NH and HI listeners subjectively evaluated the perceived disturbance from the speech- and noise maskers in the native and nonnative languages. Paper IV examined how well native and non-native stories that were presented unmasked and masked with native and non-native speech were recalled by NH listeners. Paper IV further investigated the role of working memory capacity in the episodic long-term memory of story contents as well as proficiency in native and non-native languages. The results showed that generally, the speech maskers affected performance and perceived disturbance more than the noise maskers did. Regarding the non-native target language, interference from speech maskers in the dominant native language is taxing for speech perception performance, perceived disturbance and memory processes. However, large inter- individual variability between the listeners was observed. Part of this variability relates to non-native language proficiency. Perceptual and cognitive effort may hinder efficient long-term memory encoding, even when stimuli are appropriately identified at a perceptual level. A large working memory capacity (WMC) provides a better ability to suppress distractions and allocate processing resources to meet assigned objectives. The relatively large inter-individual differences in this thesis, require an individualized approach in clinical or educational settings when non-native persons or people with hearing impairment need to perceive and remember potentially vital information. Individua  differences in the very complex process of speech understanding and recall need to be further addressed by future studies. The relevance of cognitive factors and language proficiency provides opportunities for individuals who face difficulties to compensate using other abilities.