Previous research has revealed that very young infants discriminate most speech contrasts with which they are presented whether the contrasts are native or non-native while adults have difficulty discriminating non-native speech contrasts but easily discriminate those contrasts holding meaningful (phonemic) status in their native language. Several studies have shown that this reorganization in phonetic perception from language-general perception to language-specific perception occurs at about 10 to 12 months: infants this age attend only to native phonemic contrasts. It is of interest to determine if exposure to a phonetic variant plays an important role in influencing perception. We know from previous research that absence of exposure does not always lead to a lack of discrimination. This thesis was designed to determine if exposure per se maintains discriminability. To this end English-speaking adults and infants were tested using a phonetic distinction that does not hold phonemic status in English but does occur in English. This distinction involves the phonetic variants [da] and the stop produced following /s/ transcribed as [ta]. When tested in an identification procedure, English-speaking adults identify both [da] and (s)[ta] as members of one English phonemic category (i.e. [da]). When tested in a discrimination procedure and a category change procedure, adults discriminate (s) [ta] from [da] (albeit not as well as would be expected for a native phonemic contrast). With respect to infants, 6- to 8-month-olds discriminate this distinction revealing further support for broad-based phonetic perception at this age. However, 10- to 12-month-old infants do not discriminate, suggesting that the native phonemic status of the contrast (but not exposure) is the important factor in the reorganization. Discussion centers around how these results add to the existing literature and why infants of 10- to 12-months would fail to discriminate a native phonetic distinction.

Thesis (Ph. D.)--Lehigh University, 2004. / Includes vita. Includes bibliographical references (leaves 74-85).

Previous research has revealed that very young infants discriminate most speech contrasts with which they are presented whether the contrasts are native or non-native while adults have difficulty discriminating non-native speech contrasts but easily discriminate those contrasts holding meaningful (phonemic) status in their native language. Several studies have shown that this reorganization in phonetic perception from language-general perception to language-specific perception occurs at about 10 to 12 months: infants this age attend only to native phonemic contrasts. It is of interest to determine if exposure to a phonetic variant plays an important role in influencing perception. We know from previous research that absence of exposure does not always lead to a lack of discrimination. This thesis was designed to determine if exposure per se maintains discriminability. To this end English-speaking adults and infants were tested using a phonetic distinction that does not hold phonemic status in English but does occur in English. This distinction involves the phonetic variants [da] and the stop produced following /s/ transcribed as [ta]. When tested in an identification procedure, English-speaking adults identify both [da] and (s)[ta] as members of one English phonemic category (i.e. [da]). When tested in a discrimination procedure and a category change procedure, adults discriminate (s) [ta] from [da] (albeit not as well as would be expected for a native phonemic contrast). With respect to infants, 6- to 8-month-olds discriminate this distinction revealing further support for broad-based phonetic perception at this age. However, 10- to 12-month-old infants do not discriminate, suggesting that the native phonemic status of the contrast (but not exposure) is the important factor in the reorganization. Discussion centers around how these results add to the existing literature and why infants of 10- to 12-months would fail to discriminate a native phonetic distinction. / Arts, Faculty of / Psychology, Department of / Graduate

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

Not available / text

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.

Previous research indicates that for adults and children the perception of speech can be significantly influenced by watching a speaker's mouth movements. For example, hearing the syllable /bi/ while watching a speaker mouth the syllable /vi/ results in reports of a 'heard' /vi/. Some evidence suggests young infants also may be able to integrate heard and seen speech. One theory suggests that an innate link between perception and production (Liberman & Mattingly, 1985) accounts for this phenomenon while another theory suggests that experience (e.g., producing speech sounds) may be necessary into order to develop fully the underlying representation of visible speech (Desjardins, Rogers & Werker, in press; Meltzoff & Kuhl, 1994). My dissertation addresses the above controversy by examining whether the integration of heard and seen speech is obligatory for young infants as it is for adults. In Experiment 1, 4-month-old female infants habituated to audiovisual /bi/ showed renewed visual interest to an auditory /bi/-visual NM suggesting that they may have perceived the auditory /bi/-visual /vi/ as /vi/, as do adults. In Experiment 2, neither male nor female infants showed renewed visual interest to a dishabituation stimulus which represents only a change in mouth movements. In Experiment 3, male infants looked longer to an audiovisual /bi/ than to an audiovisual /vi/ following habituation to an audio /bi/-visual /vi/, while female infants tended to look only slightly longer to an audiovisual /vi/ than to an audiovisual /bi/. Taken together these experiments suggest that at least some infants are able to integrate heard and seen speech, but that they do not do so consistently. Although an innate mechanism may be responsible for integration, a role for experience is suggested as integration does not appear to be obligatory for young infants as it is for adults.

Thesis (M.S.)--University of Texas at Dallas, 2007. / Includes vita. Includes bibliographical references (leaves 38-41)

Thesis (Ph. D.)--University of Washington, 1997. / Vita. Includes bibliographical references (leaves [84]-91).

Previous research indicates that for adults and children the perception of speech can be significantly influenced by watching a speaker's mouth movements. For example, hearing the syllable /bi/ while watching a speaker mouth the syllable /vi/ results in reports of a 'heard' /vi/. Some evidence suggests young infants also may be able to integrate heard and seen speech. One theory suggests that an innate link between perception and production (Liberman & Mattingly, 1985) accounts for this phenomenon while another theory suggests that experience (e.g., producing speech sounds) may be necessary into order to develop fully the underlying representation of visible speech (Desjardins, Rogers & Werker, in press; Meltzoff & Kuhl, 1994). My dissertation addresses the above controversy by examining whether the integration of heard and seen speech is obligatory for young infants as it is for adults. In Experiment 1, 4-month-old female infants habituated to audiovisual /bi/ showed renewed visual interest to an auditory /bi/-visual NM suggesting that they may have perceived the auditory /bi/-visual /vi/ as /vi/, as do adults. In Experiment 2, neither male nor female infants showed renewed visual interest to a dishabituation stimulus which represents only a change in mouth movements. In Experiment 3, male infants looked longer to an audiovisual /bi/ than to an audiovisual /vi/ following habituation to an audio /bi/-visual /vi/, while female infants tended to look only slightly longer to an audiovisual /vi/ than to an audiovisual /bi/. Taken together these experiments suggest that at least some infants are able to integrate heard and seen speech, but that they do not do so consistently. Although an innate mechanism may be responsible for integration, a role for experience is suggested as integration does not appear to be obligatory for young infants as it is for adults. / Arts, Faculty of / Psychology, Department of / Graduate