Faculty of Education


Acquiring the native language involves learning to perceive and produce sound structures (phonology) of the speech input. Speech to children often contains phonological modifications, and across languages the speech input to which children are exposed contains phonetic variation associated with linguistic and socioindexical information. Previous studies have investigated phonetic variation in infant-directed speech (e.g. Davis & Lindblom, 2001; Fernald et al., 1989; Kuhl et al., 1997; Snow, 1977), and differences in phonological variation between child-directed and adultdirected speech (e.g. Bernstein-Ratner, 1984a, 1984b; Lee, Davis & MacNeilage, 2008; Lee & Davis, 2010). There are, however, few studies examining how and when phonetic variation in speech to children changes after infancy, as they get older. This thesis is a longitudinal investigation of phonetic variation in mothers’ speech to children (maternal speech) in two language varieties spoken in northern Australia, Gurindji Kriol and Australian English.

Gurindji Kriol is an Australian Aboriginal mixed language that contains lexical forms and phonology from both the traditional language Gurindji and Kriol, an English-lexifier creole. There are no previous systematic quantitative studies on fricatives in Gurindji Kriol, or any Australian contact language, although impressionistically fricatives in Kriol-derived words are highly variable. Australian English also contains phonetic variation related to speech processes, such as consonant reduction in casual speech. There is, however, little prior research on phonetic variation that children are exposed to in Australian English. The purpose of this thesis was to provide quantitative analyses of fricative variation in maternal speech in Gurindji Kriol and northern Australian English as children aged from approximately 1;6 to 2;0 to 2;6. A subsidiary aim was to examine methodological issues in phonetic transcription when the transcribers are non-native speakers of the language.

This thesis contains three empirical research studies. In Study 1 we added phonetic transcription and analysis to a subsample of a corpus of naturalistic family interactions in Gurindji Kriol created by Felicity Meakins between 2003 and 2007 as part of the Aboriginal Child Language project (ACLA-1, Simpson & Wigglesworth, 2008). Speakers were three Gurindji Kriol speaking women recorded at three timepoints, when the focus children were approximately 1;6, 2;0 and 2;6. We analysed stop-fricative variation in tokens of Kriol-derived words that could potentially be pronounced with a fricative, based on words that had fricatives in their English cognates. Results showed that words containing stop-fricative variation were more likely to be open-class than closed-class, with the variable segment most frequently word-initial and at labio-dental and alveolar places of articulation. Across all tokens with potential fricatives, the likelihood of fricatives in word-initial position significantly increased when children were 2;6. In tokens of words found to contain stop-fricative variation, word-medial fricatives were significantly more likely in mothers’ speech at child age 2;6. Analyses took into account phonological environments and interspeaker differences.

Study 2 investigated fricative variation in the form of phonological reduction in northern Australian English maternal speech. A longitudinal audiovisual corpus of naturalistic family interactions was recorded and phonetically transcribed for this study. Speakers were five mothers who were native speakers of Australian English, and were recorded when their children were approximately 1;6, 2;0 and 2;6. We analysed deletion in word-initial /h/ and word-final /v/, common processes in casual speech, in mothers’ speech at each timepoint. Results showed a non-linear change in overall deletion over time within a stable set of lexical items. Between child ages 1;6 and 2;0 deletion proportionately increased in mothers’ speech, while between 2;0 and 2;6 deletion proportionately decreased.

Study 3 addressed a methodological issue of checking phonetic transcription with native speakers of Gurindji Kriol. Native speakers have implicit knowledge of Gurindji Kriol phonology that would be beneficial to understanding transcription ambiguities arising from perceptual bias, and for furthering our interpretation of phonetic variation in Gurindji Kriol. We used visual analogue scales to elicit native speaker perceptions on sound segments potentially pronounced as fricatives in Gurindji Kriol. Native speaker judgements on the scales were then compared to the IPA judgements made by non-native speaker phonetic transcribers. Results showed both agreements and discrepancies between native and non-native speakers for different types of judgements and segment word positions.

Empirical findings in this thesis are discussed in terms of processes driving change in phonetic variation in mothers’ speech to children, such as fine-tuning to children’s own receptive and productive language development. Results have implications for theoretical models of children’s phonological acquisition, which must take into account variable phonetic detail in the input. Pedagogical implications are also discussed (in Chapter 7) in terms of how teachers can use information about Gurindji children’s home language to augment their language and literacy teaching.