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Amount of speech exposure predicts vowel perception in four-to-eight-month-olds
Stockholm University, Faculty of Humanities, Department of Linguistics, Phonetics.ORCID iD: 0000-0001-7658-9307
Stockholm University, Faculty of Humanities, Department of Linguistics, Phonetics.ORCID iD: 0000-0002-8036-516X
Stockholm University, Faculty of Humanities, Department of Linguistics, Phonetics.ORCID iD: 0000-0002-7980-3601
(English)Manuscript (preprint) (Other academic)
Abstract [en]

During the first year of life, infants shift their focus in speech perception from acoustic to linguistic information. This perceptual reorganization is related to exposure, and a direct relation has been demonstrated previously between amount of daily language exposure and mismatch response (MMR) amplitude to a native consonant contrast at around one year of age. The present study investigates the same relation between amount of speech exposure and MMR amplitude to a native vowel contrast at four to eight months of age. Importantly, the present study uses spectrally rotated speech in an effort to take general neural maturation into account. The amplitude of the part of the MMR that is tied specifically to speech processing correlates with amount of daily speech exposure, as estimated using the LENA system.

National Category
General Language Studies and Linguistics
Research subject
Linguistics
Identifiers
URN: urn:nbn:se:su:diva-148556OAI: oai:DiVA.org:su-148556DiVA: diva2:1153470
Available from: 2017-10-30 Created: 2017-10-30 Last updated: 2017-11-01Bibliographically approved
In thesis
1. Perceptual reorganization of vowels: Separating the linguistic and acoustic parts of the mismatch response
Open this publication in new window or tab >>Perceptual reorganization of vowels: Separating the linguistic and acoustic parts of the mismatch response
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

During the first year of life, infants go from perceiving speech sounds primarily based on their acoustic characteristics, to perceiving speech sounds as belonging to speech sound categories relevant in their native language(s). The transition is apparent in that very young infants typically discriminate both native and non-native speech sound contrasts, whereas older infants show better discrimination for native contrasts and worse or no discrimi­na­tion for non-native contrasts. The rate of this perceptual reorganization depends, among other things, on the salience of the relevant speech sounds within the speech signal. As such, the perceptual reorganization of vowels and lexical tone typically precedes the perceptual reorganization of consonants.

Perceptual reorganizatoin of speech sounds is often demonstrated by measuring in­fants’ discrimination of specific speech sound contrasts across development. One way of measuring discriminatory ability is to use the mismatch response (MMR). This is a brain response that can be measured using external electroencephalography re­cord­ings. Pre­senting an oddball (deviant) stimulus among a series of standard stimuli elicits a response that, in adults, correlates well with behavioral discrimination. When the two stimuli are speech sounds contrastive in the listeners’ language, the response arguably reflects both acoustic and linguistic processing. In infants, the response is less studied, but has nevertheless already proven useful for studies on the perceptual reorganization of speech sounds.

The present thesis documents a series of studies with the end game of investigating how amount of speech exposure influences the perceptual reorganization, and whe­ther the learning mechanisms involved in speech sound cate­gory learning is specific to speech or domain-general. In order to be able to compare MMR results across diffe­rent age groups in infancy, a non-speech control condition needed to be devised however, to account for changes in the MMR across development that are attributable to general brain matura­tion rather than language development specifically.

Findings of studies incorporated in the thesis show that spectrally rotated speech can be used to approximate the acoustic part of the MMR in adults. Subtracting the acoustic part of the MMR from the full MMR thus estimates the part of the MMR that is linked to linguistic, rather than acoustic, processing. The strength of this linguistic part of the MMR in four- and eight-month-old infants is directly related to the daily amount of speech that the infants are exposed to. No evidence of distributional learning of non-speech auditory categories was demonstrated in adults, but the results together with previous research generated hypo­theses for future study.

In conclusion, the research performed within the scope of this thesis highlight the need of a non-speech control condition for use in developmental speech perception studies using the MMR, demonstrates the viability of one such non-speech control condition, and points toward relevant future research within the topic of speech sound category development.

Place, publisher, year, edition, pages
Stockholm: Department of Linguistics, Stockholm University, 2017. 89 p.
Keyword
language acquisition, infants, speech perception, MMR, MMN, perceptual reorganization
National Category
General Language Studies and Linguistics
Research subject
Linguistics
Identifiers
urn:nbn:se:su:diva-148559 (URN)978-91-7797-053-8 (ISBN)978-91-7797-054-5 (ISBN)
Public defence
2017-12-15, Högbomsalen, Geovetenskapens hus, Svante Arrhenius väg 12, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.

Available from: 2017-11-22 Created: 2017-10-31 Last updated: 2017-11-23Bibliographically approved

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