Previous bilingual studies showed reduced hemispheric asymmetry in visual tasks such as face perception in bilinguals compared with monolinguals, which suggested that hemispheric asymmetry in visual tasks could be modulated by experience in reading one or two languages. Here I examined whether differences in hemispheric asymmetry in visual tasks can also be observed in bilinguals who have different language backgrounds. I compared the behavior of three language groups: (1) English monolinguals, who acquire only one alphabetic language, (2) European-English bilinguals, who know two alphabetic languages, and (3) Chinese-English bilinguals, who master an alphabetic language and a logographic language; in three tachistoscopic tasks: (1) English word sequential matching task, (2) Intact-altered face judgment task, and (3) face sequential matching task. The results showed that European-English bilinguals had a stronger right visual field (RVF)/ left hemispheric (LH) advantage in the English word sequential matching task than English monolinguals and Chinese-English bilinguals, suggesting that different language learning experiences can influence how visual words are processed in the brain. However, the results showed no group difference between the left visual field (LVF)/ right hemisphere (RH) advantage in the intact-altered face judgment task and the face sequential matching task. These results suggested a modulation of language experience on visual word processing but not on face processing. In addition, I showed that the hemispheric asymmetry in visual word processing could be accounted for by a computational model that implements a theory of hemispheric asymmetry in perception (i.e. the Double Filtering by Frequency theory, Ivry & Robertson, 1998); the modeling data suggested that this lateralization difference in visual word processing may be due to both the difference in participants’ vocabulary size and the difference in word-to-sound mapping between alphabetic and logographic languages. / published_or_final_version / Psychology / Master / Master of Philosophy

Speech sounds are typically perceived categorically. The acoustic information in speech sounds is perceptually grouped into phonetic categories. It is widely known that language influences the way speech sounds are categorized. That is, one's native language influences where category boundaries are placed. However, it is less understood how bilingual listeners categorize speech sounds. There is evidence showing that bilinguals have different category boundaries from monolinguals, but there is also evidence suggesting that bilinguals have different category boundaries depending on the language they are using at the moment. This phenomenon has been referred as the double phonetic boundary. The goal of this investigation was to verify the existence of the double phonemic boundary in bilingual listeners. As has been done in other studies, bilingual speakers of Spanish and English were asked to identify the speech sound /ta/ from a 10-token speech continuum ranging in VOT from /da/ to /ta/ in two language contexts. In this study, however, two additional procedures were carried out. First, English monolinguals were asked to identify the continuum in two language contexts. It was expected that bilinguals, but not monolinguals, would show a double phonetic boundary. Second, while participants' behavioral measures were assessed, electrophysiological measures [event-related potentials, (ERPs)] also were recorded. This was done in order to observe how speech sounds are represented in the brain. It as expected that bilinguals, but not monolinguals, would show different ERP amplitudes across language contexts. The behavioral results showed that phonemic boundaries did not differ across language contexts for either bilinguals or monolinguals. Further analyses showed bilinguals, but not monolinguals, perceived specific speech sounds--in the "ambiguous zone"--differently across language contexts. The electrophysiological results showed that the ERPs of bilinguals, but not monolinguals, differed across language contexts. Interestingly, behavioral measures correlated significantly with electrophysiological measures only in bilinguals. This result showed that the ERP amplitude was in accordance with the number of sounds perceived as 'ta' across language contexts. The challenges of testing the double phonemic boundary are discussed, along with the limitations of the methodology used in this study. / text

This thesis examines phonological awareness and literacy in monolingual and bilingual children. Experiment 1 shows that 5-6 year old Spanish-monolingual, English-monolingual and Spanish-English-bilingual children show the same pattern of development of phonological awareness. However, the degree of awareness of each unit is influenced by linguistic background. Spanish children are more aware of vowels and rimes than English children. English children are more aware of syllables than Spanish children. Bilingual children are more aware of syllables in Spanish than Spanish-monolinguals and more aware of vowels in English than English-monolinguals. Hence they show transfer of phonological awareness across languages. All three groups also show a different relationship between phonological awareness and reading. Experiment 2 shows that bilinguals are more aware than English monolinguals of vowels that exist in both languages (tense-vowels). Moreover, this enhanced awareness extends to vowels that do not exist in Spanish (lax-vowels). It is concluded that exposure to two languages enhances analysis of phonology as well as encouraging transfer of awareness. Experiment 2 also shows that Spanish-speakers read and spell vowels more accurately than English-speakers. Bilingual children read English vowels more accurately than English-monolinguals. This suggests they understand the orthographic representations of English vowels at least as well as monolinguals. However, they spell vowels less accurately. This may be because bilinguals misapply Spanish phoneme-to-graphemecorrespondences when spelling English vowels. The English and Spanish vowel systems differ more than their consonant systems. Experiment 3 shows that sensitivity to the four consonant types (stops, fricatives, nasals and liquids) is similar, and correlates with reading ability, in all groups. This suggests that bilinguals may only transfer awareness between English and Spanish of units that are linguistically dissimilar in each. Experiment 4 compared the awareness of the two consonants in word-medial double-consonants (e.g. the 'c' and 't' in mactan). Although only Spanish-speakers used syllable boundaries to analyse these consonants they made a similar number of errors to English-speakers. However, all groups used syllable boundaries to read and spell wordmedial double-consonants. Collectively, these results suggest that differences in phonological and orthographic structure between languages encourage different approaches to the acquisition of literacy. Future research should investigate how these differences may be exploited to facilitate literacy acquisition in each group.

Purpose: The aim of this research was to examine the relationship between stuttering and bilingualism to hemispheric asymmetry for the processing and production of language. Methods: A total of 80 native speakers of German were recruited for the study, ranging in age from 15 to 58 years. Out of those 80 participants, 40 participants were also proficient speakers of English as a second language (L2). The participants were organised into four speaker groups (20 per group) according to language ability and speech status, consisting of monolinguals who stutter (MWS), monolinguals who do not stutter (MWNS), bilinguals who stutter (BWS), and bilinguals who do not stutter (BWNS). Each of the four groups comprised 12 males and 8 females. All participants completed a battery of behavioural assessments measuring functional cerebral hemispheric asymmetry during language processing and production. The behavioural tests included (1) a dichotic listening paradigm, (2) a visual hemifield paradigm, and (3) a dual-task paradigm. Results: Overall, the results showed no significant differences in language lateralisation between participant groups on the three behavioural tests. However group differences were identified in regard to executive functions on the visual hemifield and dual-task paradigms. Both bilingual groups showed significantly faster reaction times and fewer errors than the two monolingual groups on the visual hemifield paradigm. The bilingual groups also performed similarly on the dual-task paradigm, while the MWS group tended to show greater task disruption. No meaningful relationship was found between stuttering severity and the majority of results obtained for the test conditions. However, all four language modalities were found to correlate significantly with results obtained for the visual hemifield and dual-task paradigms, suggesting that performance on these tests increased with higher L2 proficiency. Conclusion: Although no differences in language lateralisation were found, it appears that bilingualism had a greater influence on functional cerebral hemispheric processing than stuttering. A prevailing finding was that bilingualism seems to be able to offset deficits in executive functioning associated with stuttering. Brain reserve and cognitive reserve are thought to have a close interrelationship with the executive control system. Cognitive reserve may have been reflected in the present study, resulting in a bilingual cognitive advantage. Hence, the results of the present study lend support to previous findings implicating the benefits of bilingualism.

published_or_final_version / abstract / Linguistics / Master / Master of Arts

published_or_final_version / Psychology / Doctoral / Doctor of Philosophy

published_or_final_version / Psychology / Doctoral / Doctor of Philosophy

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