Fourteen-month-old infants raised in a monolingual English environment confuse phonetically similar words in a word-object association task (Stager & Werker, 1997); however, older infants, who are more proficient at word learning, do not (Werker, Corcoran, Fennell, & Stager, 2000). This temporary confusion of phonetic detail occurs despite the fact that 14- month-old infants still have the ability to discriminate native language phonemes in speech perception tasks not involving word learning. Therefore, it has been hypothesized that 14- month-olds fail because linking words to objects is difficult at the beginning stages of word learning, leaving infants with insufficient attentional resources to listen closely to the words. Extending this hypothesis to infants raised in a bilingual environment generates two possibilities. (1) Bilingual infants will not show the temporary deficit at 14 months. As a function of growing up with two languages, they will have already developed a greater awareness of the sounds of words because more detail is needed to discriminate words in two languages. (2) Bilingual infants will perform at least as poorly as infants being raised with only English because of the cognitive load of learning two languages. Bilingual infants of 14 months were tested in the word-object association task using the phonetically similar labels 'bih' and 'dih' paired with two distinct and colourful moving objects. Following habituation, infants were tested on their ability to detect a 'switch' in the word-object pairing. Bilingual language exposure was assessed with a structured parental interview. The 16 infants included in the sample had been exposed to two languages from birth and had at least 30% exposure to one language and no more than 70% to the other. The results showed that, like the monolingual-learning infants of the same age, the 14-month-old bilingual-learning infants confused similar sounding words. These data are consistent with the cognitive load hypothesis, and argue against the proposition that early bilingual exposure facilitates metalinguistic awareness. Future research with slightly older bilingual word learners who have reached the age at which monolingual infants can successfully learn phonetically similar words will help to clarify if these bilingual infants maintain, or diverge from, a monolingual pattern of development.

The emergence of language is a phenomenon that lies at the core of higher human cognition and which continues to be the source of controversy and debate. In a series of three studies, the present thesis examined issues pertaining to language acquisition, (i) providing insight into the origins of language by addressing the question of whether the basis of babbling is fundamentally motoric or linguistic, (ii) positing new properties of babbling in order to discriminate between the linguistic and non-linguistic behaviors produced by babies, and (iii) describing the processes underlying babies' transition from babbles to first words. In Manuscript 1, using Optotrak, the manual activity of six hearing babies was examined (at ages 6, 10 and 12 months; 3 babies were exposed to a signed language and 3 to a spoken language). Analyses revealed that only the sign-exposed babies produced linguistic activity (manual babbling) at a frequency of approximately 1 Hz and subsequent videotape analyses revealed that babbling was produced in the linguistic signing space. Non-linguistic activity was produced by both groups of babies at approximately 2.5 Hz and fell outside the signing space. In Manuscript 2, the oral activity of ten hearing babies acquiring a spoken language was examined for evidence of mouth asymmetry (between ages 5 and 12 months). Right mouth opening was observed only while the babies were babbling (reflecting left hemisphere language specialization), as contrasted with equal or left mouth opening for non-linguistic oral activity. In Manuscript 3, a combination of sources (videotapes, parental reports, interviews, and experimenter notes) was used to examine how six hearing bilingual babies acquired the meanings of words/signs across their two languages (from ages 7 to 26 months; 3 babies were exposed to a signed and a spoken language and 3 to two spoken languages). The babies constrained, organized, and used their first words/signs in simila

Fourteen-month-old infants raised in a monolingual English environment confuse phonetically similar words in a word-object association task (Stager & Werker, 1997); however, older infants, who are more proficient at word learning, do not (Werker, Corcoran, Fennell, & Stager, 2000). This temporary confusion of phonetic detail occurs despite the fact that 14- month-old infants still have the ability to discriminate native language phonemes in speech perception tasks not involving word learning. Therefore, it has been hypothesized that 14- month-olds fail because linking words to objects is difficult at the beginning stages of word learning, leaving infants with insufficient attentional resources to listen closely to the words. Extending this hypothesis to infants raised in a bilingual environment generates two possibilities. (1) Bilingual infants will not show the temporary deficit at 14 months. As a function of growing up with two languages, they will have already developed a greater awareness of the sounds of words because more detail is needed to discriminate words in two languages. (2) Bilingual infants will perform at least as poorly as infants being raised with only English because of the cognitive load of learning two languages. Bilingual infants of 14 months were tested in the word-object association task using the phonetically similar labels 'bih' and 'dih' paired with two distinct and colourful moving objects. Following habituation, infants were tested on their ability to detect a 'switch' in the word-object pairing. Bilingual language exposure was assessed with a structured parental interview. The 16 infants included in the sample had been exposed to two languages from birth and had at least 30% exposure to one language and no more than 70% to the other. The results showed that, like the monolingual-learning infants of the same age, the 14-month-old bilingual-learning infants confused similar sounding words. These data are consistent with the cognitive load hypothesis, and argue against the proposition that early bilingual exposure facilitates metalinguistic awareness. Future research with slightly older bilingual word learners who have reached the age at which monolingual infants can successfully learn phonetically similar words will help to clarify if these bilingual infants maintain, or diverge from, a monolingual pattern of development. / Arts, Faculty of / Psychology, Department of / Graduate

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Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI/Dissertation Abstracts International.

In speech perception tasks young infants show remarkable sensitivity to fine phonetic detail. Despite this impressive ability demonstrated at early ages, studies of word learning in young toddlers indicate that they have difficulty learning similar-sounding words. This evidence suggests that infants may not be using this speech-perception ability as they begin to learn words. The studies in this thesis were designed to test how infants' speech-perception skills are used in the early stages of word learning. Using a simple habituation procedure, we have shown in earlier work that 14-month-old infants, but not younger infants, are able to learn the association between novel nonsense words and objects (Werker, Cohen, Lloyd, Casasola, & Stager, 1998). The current series of experiments used this simple habituation procedure to test whether infants use minimally contrastive phonetic detail in the very early stages of word learning. In this thesis, I show that 14-month-old infants, who are on the cusp of word learning, while still able to discriminate phonetically-similar words in a speech perception task, do not incorporate minimally contrastive phonetic detail when first forming word-object associations. Infants of 8 months of age do, however, appear to use fine phonetic detail in a similar task. Taken together, these results suggest a decline in the phonetic detail used by infants as they move from processing speech to learning words. I hypothesize that this decline may occur as infants move from treating the task as one of speech perception to treating the task as one of word learning.

In speech perception tasks young infants show remarkable sensitivity to fine phonetic detail. Despite this impressive ability demonstrated at early ages, studies of word learning in young toddlers indicate that they have difficulty learning similar-sounding words. This evidence suggests that infants may not be using this speech-perception ability as they begin to learn words. The studies in this thesis were designed to test how infants' speech-perception skills are used in the early stages of word learning. Using a simple habituation procedure, we have shown in earlier work that 14-month-old infants, but not younger infants, are able to learn the association between novel nonsense words and objects (Werker, Cohen, Lloyd, Casasola, & Stager, 1998). The current series of experiments used this simple habituation procedure to test whether infants use minimally contrastive phonetic detail in the very early stages of word learning. In this thesis, I show that 14-month-old infants, who are on the cusp of word learning, while still able to discriminate phonetically-similar words in a speech perception task, do not incorporate minimally contrastive phonetic detail when first forming word-object associations. Infants of 8 months of age do, however, appear to use fine phonetic detail in a similar task. Taken together, these results suggest a decline in the phonetic detail used by infants as they move from processing speech to learning words. I hypothesize that this decline may occur as infants move from treating the task as one of speech perception to treating the task as one of word learning. / Arts, Faculty of / Psychology, Department of / Graduate

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (B.Sc)--University of Hong Kong, 2005. / "A dissertation submitted in partial fulfilment of the requirements for the Bachelor of Science (Speech and Hearing Sciences), The University of Hong Kong, June 30, 2005." Also available in print.

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 187-207).