Developmental changes in speech categorization during later childhood and the effect of language exposure

• In Event: Bilingualism - later childhood

Abstract

Previous studies suggest that speech categorization is established during the first year of life (Werker & Tees, 1984; Kuhl et al., 2006). However, more recent work suggests protracted development through adolescence (McMurray et al., 2018). While the early development has been thought to be driven by the statistical properties of the input, it is unclear if this late phase is also input driven. We asked whether being exposed to another language in early childhood leads to different patterns of speech categorization.

Many children around the world hear more than one language. For multilingual children, the challenge begins when schooling starts. They may be extensively exposed to the phonemes of the dominant language until well after infancy, providing a unique window of opportunity to examine plasticity. Other children may grow up monolingual, but in an environment heavily colored by a range of accents. This too could lead to differences in how they categorize speech.

The current study uses the Visual Analogue Scaling (VAS) task (Kong & Edwards, 2011; Kapnoula et al., 2017) as a fine-grained measure of multiple aspects of speech categorization. Participants heard tokens from a speech continuum (e.g., beach/peach as well as vowel continua) and made continuous ratings about how /b/- or /p/-like the sound is. The trial-by-trial ratings can reveal how gradient or categorical children are but also how consistently they respond.

The first ongoing project (current n=31, planned n=60) tested English-speaking school-aged children (6-11 years old) using the VAS task. We measured the language diversity around the children using both a language background and a social network survey. Based on the children’s parents’ responses to our social network questionnaire, children were categorized as language-diverse and language-non-diverse. Our preliminary findings show that language-diverse children make use of acoustic cues in a more gradient way than language-non-diverse children, presumed to lead to greater flexibility.

The second ongoing study examined the effect of the age of beginning exposure to a language by testing adults (Mean age=31, Min=19, Max=56, n=65, planned n=90) who should have had substantial exposure to English, but who vary in when their exposure started. Participants were drawn from three groups: monolingual English speakers (n= 22), Spanish heritage speakers who are dominant in English (n= 36), and English language learners who acquired English after the age of 10 (n= 7). Our preliminary findings show no difference between the monolingual and the Spanish heritage speakers in the VAS task. However, both groups differed from the English as a second language learner group.

These findings suggest that the development of speech perception is not finished during the first year of life, but that it continues to be shaped by the developmental changes across the lifespan (McMurray et al., 2018). Importantly, multilingual exposure is not detrimental for perceptual expertise in the majority language. Individuals who have diverse linguistic exposure but are dominant in English show virtually no differences compared to the monolingual English participants. We argue for theories that can integrate individual differences (McMurray et al., 2002) in multilingual populations.

Authors

• Ethan Kutlu, University of Iowa
  Presenting Author

• Samantha Chiu

• Abigail Fergus

• Alexandra Fell

• Jamie Klein-Packard

• Keith S Apfelbaum

• Bob McMurray, University of Iowa