Linguistically diverse children's speech processing in noise

Many children in primary school listen and learn through their second language, often under noisy listening conditions. This thesis is based on assessments of 7 to 9-year-old primary school children (N=98) attending Swedish schools in areas of low socio-economic status where most students had immigration background. The overall aim of this thesis was to increase knowledge on how multitalker babble noise affects speech processing in primary school children of cultural and linguistic diversity. The first objective was to develop and evaluate a listening comprehension task to increase reliability in assessments of young primary school children of cultural and linguistic diversity. The developed task, called Lyssna, Förstå och Minnas (English: Listen, Comprehend, and Remember; LFM) was evaluated and considered suitable for investigating effects of adverse listening conditions in young primary school children of cultural and linguistic diversity. The second objective was to investigate how multitalker babble noise affects speech processing, memory retention, listening effort and fatigue in these children. In summary, the findings indicate that short-term exposure to multitalker babble noise impairs children's immediate comprehension and recall of spoken information. However, this adverse effect on comprehension and recall may be temporary and it can potentially be normalized with memory consolidation and the process of recall. The third objective was to investigate the role of school language (Swedish) exposure on speech processing, memory retention, listening effort and fatigue under different listening conditions. The findings showed that increasing school language exposure was associated with increasing comprehension and memory for spoken Swedish narratives.
However, the results were inconclusive as to the effect of multitalker babble noise, suggesting that children with little exposure to and knowledge in the school language may be more susceptible to the negative effects of multitalker babble noise on tasks which rely highly on adequate speech perception
and fast processing and switching between tasks, but not on longer narrative tasks such as the LFM task. Using pupillometry, a physiological measure of listening effort and fatigue,the results pointed to increased listening effort and listening imposed fatigue in more challenging listening conditions, an effect which was driven by children with less experience in the school language.The last objetive was to identify within-listener factors important for speech processing in quiet and in multitalker babble noise. The importance of working memory capacity was a key finding. Implicit working memory processing, as measured by nonword reptition, was a strong predictor for speech processing in both quiet and in noise. Further, age differences in working memory processing was found, suggesting that younger children may have a more difficult time to use explicit working memory processing for comprehension in noise, as compared to their older peers.