Developmental Trajectories Of Mandarin Lexical Tone Identification By Young Children In Noise And Its Relation With Working Memory

The goal of this study was to examine the developmental trajectories of identification of Mandarin lexical tones for children with normal hearing in two noise conditions: speech-shaped noise(SSN)and multi-talker babble noise(babble).The study also aimed to investigate the association between speech perception in noise and working memory capacity.We asked the following questions: 1)What are the developmental trajectories of children’s tone identification ability in SSN and babble noise? 2)Is working memory capacity related to speech perception in noise?Ninety-three children aged 5-8 years with normal hearing and twenty-three young adults completed categorical identification of two tonal continuums: Tone 1-4 continuum(Experiment1)and Tone 2-3 continuum(Experiment 2)in quiet,SSN and babble noise at a signal-to-noise ratio(SNR)of 0 d B.Boundary position and boundary width were measured.Participants also completed standardized measures of working memory capacity(Experiment 3)including a forward digit span test and a backward digit span test.Correlation analyses between digit span score and boundary width(proved to be a useful measure of perception performance)were conducted twice for an overall conclusion(children aged 5-8 years as one group)and more specific results for children of different developmental stages(children aged 5-6 years as one group;children aged 7-8 years as another group).Results of Experiment 1 showed that six-year-old children have achieved the adult-like ability of categorical identification of Tone 1-4 continuum in SSN and babble noise at 0 d B.Results of Experiment 2 showed that six-year-old children were able to identify Tone 2-3continuum as adults in SSN.However,when Tone 2-3 continuum was masked by babble noise,eight-year-old children still performed very poorly.Greater working memory capacity was associated with better tone identification for children aged 5-6 years in both tonal continuums in SSN and babble conditions;but for children aged 7-8 years,the effect of working memory capacity only existed in Tone 2-3 continuum in SSN.The present study showed that speech perception in babble noise took longer to achieve adult-like competence than in SSN.Moreover,there were significant interactions between masker type and target complexity,indicated by Tone 2-3 continuum being more susceptible to interference from babble noise.Our study also suggested that the association between working memory capacity and speech perception in noise varied with developmental stage,stimulus complexity and masker type.Working memory capacity was positively correlated with speech perception in noise only when the listening task was of moderate difficulty for school-age children.The findings of this study have clinical and theoretical implications for the development of children’s tone perception in daily environments.