Oestrogen decline during the menopause leads to decline in cognitive performance because oestrogen receptor sites are found in the prefrontal cortex and hippocampus of the female brain, areas associated with memory and attention functions. Extensive research over the past two decades has tested the effects of administering Hormone Replacement Therapy (HRT) to maintain oestrogen levels. MRI studies have shown improvements in hippocampal volume and frontal functions with HRT, but evidence for associated improvements in verbal memory performance has been mixed. Some studies have even found detrimental effects of HRT, leading to the suggestion of a critical period for HRT administration relative to menopause. Oestrogen receptor sites are found in frontal brain regions associated with working memory (WM) functions including attention. These functions have been researched less than verbal memory, but with similarly mixed findings. The research reported in this thesis tested the critical period hypothesis in relation to WM. Study one tested the prediction that HRT will benefit WM if the therapy is initiated during the peri-menopause, and will harm it if initiated post-menopause. A naturalistic sample of 121 women were recruited, comprising women who varied in the time they had begun taking HRT, and menopausal status-matched controls who had never taken HRT. Participants completed three tests of WM span and the Sustained Attention to Response Task (SART) on two occasions 12 months apart. WM performance supported the critical period hypothesis, with women who had begun the therapy after the menopause displayed worsened WM capacity when compared to peri-menopausal initiators and post-menopausal women with no history of HRT use. At one year follow up, postmenopausal HRT users were still underperforming compared to peri-HRT initiators and those in the post-menopausal stage with no history of HRT use. No significant differences were identified between groups on the SART. The effects of natural supplements on physical symptoms of the menopause have been researched, but there is little research on their effects on cognitive symptoms and none specifically testing the critical period hypothesis. Study two tested the effects of soya isoflavones on WM during peri- and post-menopausal stages. One hundred and twelve peri- and post-menopausal women were randomly allocated to receive either placebo or 100mg soya supplement in capsules daily for three months. Participants and researcher were blind to this allocation. Participants completed two tests of WM span and two Sustained Attention (SA) tasks at baseline, after three months of soya/placebo, and after a further three months without supplement. There was no effect of isoflavones on cognition, regardless of time of initiation of the supplement. This thesis offers a unique contribution to the literature, by establishing empirically that HRT may have long-lasting benefits for WM if administered in the peri-menopause period, and detriments if taken post-menopause. There was no evidence that administration of soya-based phytoestrogens for three months peri- or post-menopause replicated these effects of HRT on cognition.

Previous research done in sociophonetic variation of second language speakers has often looked at constraints of formality affecting degree of foreign accent and how this degree of formality can have effects on what speaking styles speakers choose to employ. Furthermore, other social constraints of convergence and divergence of speech affect speaker speaking style. However, no known previous research has examined interdental fricative /θ ð/ substitution based on each speaker's interlocutor. This study explores second language speakers' English interdental fricative substitution sounds in terms of sociophonetic variation of formality and speaker interlocutor(s). Five native language pairs of Arabic, Cantonese, French, Portuguese, and Vietnamese origin were part of the study, comprising ten participants in total. The study finds age of English onset, as verified by the literature, to be the most determining factor for accurate articulation of these marked fricatives. However, other constraints for substitution choice are at hand including phonological limitations and estimated linguistic experience based on demographic information given by survey participants. The primary aim of the study is to associate some of the interdental fricative substitutions with a social variable. Data for the study include recordings of each participant reading a poem by him/herself, a dialogue with the other same native language participant, and a dialogue with a native speaker of American English. The data analysis examined the replacement sounds in terms of native language background, linguistic experience variables, and phonological constraints. In addition, quantities and ratios of specific replacement sounds for each participant per recording and per native language pair were compared and contrasted to find if speech accommodation theory (SAT), as proposed by Giles et al. (1991), played a role in any of the participants' choices for substitution. The study finds both convergence and divergence of interdental fricative substitutions to be characteristic of speakers with less linguistic experience in English. An additional stronger finding is that most participants' most common sound substitutions for the voiced and voiceless interdental fricatives were independent in place and manner, the voiced most commonly replaced by dental and alveolar plosives [ḏ d] and the voiceless most commonly replaced by labiodental fricative [f], which could be an indication of each fricative's acoustic and phonemic representation in each non-native speaker's phonological component, supported by findings of Brannen (2002). Some literature suggests that varying values of [continuant] in speakers' native languages are the means by which speakers choose the replacement sounds they do. However, such an explanation cannot be the only valid one when inherent variability comes into play and different places and manners of articulation are chosen for both interdental fricatives.

Significant research has been done regarding the influence of age of acquisition (i.e., the age at which one is exposed to a second language (L2)) on L2 learning (e.g., Johnson & Newport, 1989; Bialystock & Hakuta, 1999). Some researchers have shown that bilinguals who have learned their second language early in life may differ in their fluency from bilinguals who learned their second language later in life (White & Genesee, 1996; Flege, 1999). Specifically, studies have suggested that bilinguals who have not acquired their L2 by puberty will never acquire native-like proficiency (Lenneberg, 1967); however, others claim that there is not one particular age after which native-like language proficiency cannot be achieved (Birdsong and Molis, 1998; Flege; 1999). However, little research has been done regarding the effect that age of acquisition has on how bilinguals code switch and what rules govern this code-switching. Early research by Poplack (1980) found that late (i.e., those who learned the L2 in adulthood), less fluent bilinguals had different code switching tendencies than early (i.e., those who learned L2 in childhood), more fluent bilinguals. Lipski (1985) suggested that early bilinguals will engage in intrasentential switching while late bilinguals will rarely do so. In the present study, 26 early and late Spanish-English bilingual speakers made acceptability judgments on intra- and intersentential switches. Results indicate that there is no statistical difference between early and late bilinguals when responding to whether a mix was good or bad, and how good or bad a mix was. There were, however, trends in the results which indicate that early bilinguals may respond faster to code switches than late bilinguals, suggesting that early and late bilinguals may process language differently. Further research is needed to confirm this finding.

The question of the asset of early foreign language learning is a frequently discussed topic. Following prevailing opinion in society, that ‚the sooner, the better ', the beginning of compulsory foreign language learning is continually shifting in lower grades at primary school. A lot of children have already started with foreign language learning in kindergarten. Researches, which support the benefits of the approach, focus on a very narrow aspect of foreign language acquisition (pronunciation) or survey these facts with a specific group of inhabitants (immigrants). As experts point out, there is no significant benefit of early instructions ascertained in the Czech Republic. However, the research focused only on adults. We do not have any further evidence of the advantages of starting to learn a foreign language early. Therefore, the author focused on comparing the level of foreign language competences of two groups of pupils after their two-year compulsory instructions of English at primary school. The aim was to compare the level of their language competence in English and the learners' potential difficulties by the learners with early learning experience and by the learners without previous experience of foreign language learning before the beginning of compulsory learning at primary school....

Text in English / One of the critical challenges associated with migration is a need to acquire a destination language, which has never been an easy experience for immigrants. This study aims at exploring and analysing experiences of Malawian immigrant labourers in their process of acquiring spoken skills of isiZulu in Durban. In order to understand the phenomenon under investigation better, this study used a qualitative research approach and adopted a phenomenological research design. The data for this study was collected using semi structured one-to-one interviews. The data were analysed using content analysis method and was approached and discussed in light of Schumann‟s (1986) Acculturation Model and frame works and a destination–language acquisition model of Chiswick and Miller (2001). Empirical findings from this study have shown that adults; just like children, are also capable of mastering a second language if they can manage both social and psychological factors that impede acquisition. / Linguistics and Modern Languages / M.A. (Linguistics)

Text in English / One of the critical challenges associated with migration is a need to acquire a destination language, which has never been an easy experience for immigrants. This study aims at exploring and analysing experiences of Malawian immigrant labourers in their process of acquiring spoken skills of isiZulu in Durban. In order to understand the phenomenon under investigation better, this study used a qualitative research approach and adopted a phenomenological research design. The data for this study was collected using semi structured one-to-one interviews. The data were analysed using content analysis method and was approached and discussed in light of Schumann‟s (1986) Acculturation Model and frame works and a destination–language acquisition model of Chiswick and Miller (2001). Empirical findings from this study have shown that adults; just like children, are also capable of mastering a second language if they can manage both social and psychological factors that impede acquisition. / Linguistics and Modern Languages / M. A. (Linguistics)