This PhD thesis contributes new empirical knowledge to the question of what paths bilingual acquisition of sound structure can take in early simultaneous bilinguals. The issues of language differentiation and interaction are considered in their relationship to language input, crosslinguistic structure and longitudinal effects. Two Russian-Scottish English subjects aged between 3;4 and 4;5 were recorded longitudinally. Russian was spoken in their families, and Scottish English in the community (Edinburgh, UK). The family environments were similar, but one subject had received substantially more input in Russian than the other one. We addressed the detail of their production of prominent syllable-nuclear vowels in Scottish English and in Russian with regard to their vowel quality, duration and vocal effort. Language differentiation and interaction patterns were derived by accounting for the language mode, and by statistical comparison of the crosslinguistic structures to the speech of monolingual peers (n=7) and adults (n=14). Subjects' bilingual results revealed both substantial language differentiation and systematic language interaction patterns. The extent of language differentiation and directionality of interaction depended on the amount of language exposure. Its directionality did not necessarily depend on the markedness of the crosslinguistic structures, and could be bi-directional for the same properties. Longitudinally, language differentiation increased, while interaction reduced. The amount of reduction depended on both language input and the structural complexity of the languages with segmental tense/lax contract and complex postvocalic vowel duration conditioning showing more persistent language interaction effects. The results confirmed the importance of language input. We showed that in bilingual phonological development language interaction should be considered as a normal but non-obligatory process. Besides, some structurally complex processes potentially explainable by 'markedness' (applied to isolated segments) could rather be explained by lexical and phonotactic factors.

Language impairment is a key characteristic of many developmental disorders, with the relationship between linguistic and cognitive ability a critical topic for research in this field. Speech (articulation and phonology) and prosody have largely been absent from these discussions, perhaps because they are not universally impaired. The portfolio of published research critically appraised here addresses the relationships between speech and prosody and other domains, such as language and cognition, in two conditions in which disordered speech is common: primarily at the suprasegmental level in autism and at the segmental level in Down’s syndrome. Speech disorders were found in both conditions, though speech was much more severely impaired in Down’s syndrome. Errors were typically categorised as delayed phonological processes, implying a linguistic cause. However, through fine phonetic transcription and instrumental techniques it was shown that both conditions also presented with distortions that were more phonetic in nature and with non-developmental errors. Severity of speech disorder was not related to cognitive or linguistic ability as measured by standardised assessments, suggesting that a generalised delay in language or cognition was not the cause of disordered speech. In autism minor delays and distortions may be due to a lack of ability to identify with peers and impaired theory of mind, whereas in Down’s syndrome anatomical differences and difficulty with motor planning are likely causes. Both linguistic and paralinguistic prosody were found to be disordered in children with autism and correlations with linguistic ability were found. However, disordered prosody is more likely to be due to impaired theory of mind or weak central coherence than a result of delayed language. Both autism and Down’s syndrome present with speech that is disordered rather than simply delayed and this is unlikely to be due to delayed language, suggesting that specific, targeted intervention may be warranted.

This thesis is concerned with two different accounts of how speakers coordinate conversation. In both accounts it is suggested that aspects of the manner in which speech is performed (its disfluency and its rate) are integral to the smooth performance of conversation. In the first strand, we address Clark's (1996) suggestion that speakers design hesitations, such as filled pauses (e.g. uh and um), repetitions and prolongations, to signal to their audience that they are experiencing difficulties during language production. Such signals allow speakers to account for their use of time, particularly when they experience disruptions during production. The account is tested against three criteria, proposed by Kraljic and Brennan (2005), for evaluating whether a feature of speech is being designed: That it be produced with regularity, that it be interpretable by listeners, and that its production varies according to the speaker's communicative intention. While existing literature offers support for the first two criteria, neither an experiment with dyads nor analyses of dialogue in the Map Task Corpus (MTC; Anderson et al., 1991) found support for the third criterion. We conclude that, rather than being signals of difficulty, hesitations are merely symptoms which listeners may exploit to aid comprehension. In the second strand, we tested Wilson and Wilson's (2005) oscillator theory of the timing of turn-taking. This suggests that entrainment between conversational partners' rates of speech allow them to make precise predictions about when each others' turns are going to end, and, subsequently, when they can begin a turn of their own. As a critical test of the theory, we predicted that speakers who were more tightly entrained would produce more seamless turn-taking. Again using the MTC, we found no evidence of a relationship between how closely entrained speakers were and how precisely they timed the beginning of their turns relative to the ends of each others' turns.

Speech production in children with Down’s syndrome (DS) has been found to be variable and inconsistent. Errors are concentrated in consonants that are typically late developing, such as fricatives. It has been suggested that inconsistency in speech production in DS is a result of a motor speech deficit but there is little detailed articulatory evidence to support this claim. This study (with data from MRC grant ‘Assessment and Treatment of Impaired Speech Motor Control in Children with Down's syndrome’ (G0401388)) provides a detailed phonetic analysis of the voiceless sibilants /s/ and /ʃ/, in a group of young people with DS, by means of auditory and articulatory analysis. The aim of the study is to assess fine motor ability and articulation variability at word level production in a group of speakers with well-established difficulties in speech articulation. The study analysed data from 25 children with DS, 10 typically developing children and 8 adult speakers, recorded using EPG. Perceptual measures were compared with quantitative analyses of EPG data, along with visual analysis of articulation patterns based on a new set of articulation taxonomies. The data is presented by group and in the form of 5 case studies. The case studies provide a means to analyse the relationship between articulation and auditory information in detail and to compare these with supplementary motor control measures. The results show presence of atypical articulation patterns for speakers with DS for both perceptually acceptable tokens, and those in error. Higher levels of within-speaker articulation variability are presented in comparison to the TD control group. Further findings suggest presence of articulation patterns in the TD speakers previously unidentified in EPG studies. Similar to previous studies, the results find that speakers with DS are a highly variable group and that speakers display a combination of typical and atypical speech patterns, influenced by speech motor control difficulties.

Acquired hearing impairment affects one in six people in the United Kingdom. The process of becoming hearing impaired and seeking help is different for each individual and consequently very little is known about their personal experience of this journey. The aim of this thesis was to explore the essence of the experience of acquiring hearing impairment from the individual’s perspective, in order to better understand and meet the needs of clients seeking aural rehabilitation. Data was generated in the Phenomenological tradition using unstructured interviews and analysed using a constant comparison method drawn from Grounded Theory. Participants were recruited from the UK and the USA. Individual participant’s experience ranged from those who had not yet approached services, to those who had worn hearing aid/s for several years. Data is comprised of 24 recorded interviews, reflective journals, field notes and memos. Each interview, journal, field note and memo was coded and analysed to identify a core category. The results produced categories that identified stages the individual experiences when acquiring hearing impairment, and a core category, “Preserving the social identity” emerged. Most of the data was generated from interviews and focus groups but additionally a comprehensive audiological assessment was carried out with ten of the participants in order to compare their perception of their hearing before and after assessment. The assessment included taking a detailed medical and social history, performing otoscopy, pure tone audiometry, tympanometry, speech testing and the random gap detection test. This thesis adds to the body of knowledge about the personal experience of acquiring hearing impairment within the framework of Social Identity Theory. It proposes a theory of how individuals experience and adapt to changes in their social identity, and proposes that rehabilitation needs to be available at a much earlier stage than hearing aid fitting. It must also be multifaceted and multidisciplinary in order to meet the needs of the individual and their significant others at various stages in their journey. Finally it identifies an unmet need within Audiology provision and suggestions are made for service development and further areas of research.

Background: Voice quality in Down’s syndrome (DS) is accepted as unusual, often perceived as harsh and whispery with lower pitch and altered nasal resonance. Less is known about the resulting impact, particularly in relation to how children and young people with DS are accepted by their peers. Method: This is a quantitative study of the voice quality of children and young people with DS compared to age-matched typically-developing (TD) controls. Expert raters use the Vocal Profile Analysis Scheme to perceptually rate voice, which is compared to instrumental analysis of fundamental frequency, perturbation measures and spectral tilt. The impact of typical and atypical voice quality is evaluated in a study of listener judgments of character, ability, age, gender and social desirability using a specially designed semantic-differential questionnaire completed by special-needs and mainstream education staff and TD peers based on audio-recordings. Results: Perceptually, a number of features, including lip, tongue and jaw settings, pharyngeal constriction and respiratory support were found to be atypical compared to controls, whilst other features, notably phonation type and nasality, echoed typical patterns but were more severe in presentation in the speakers with DS. Contrary to hypotheses only spectral tilt differed significantly in instrumental analysis. All groups of raters judged the speakers with DS significantly more negatively than controls across all questionnaire parameters. TD peers showed a strong preference for the company of TD children over those with DS. Conclusions: Perceptual differences are evident in the voices of children with DS, but these are not always supported by instrumental findings, perhaps indicating that the constellation of differences give rise to more negative perception. Close agreement between education staff groups suggests that children with DS are no more disadvantaged by the perception of teachers in mainstream than in special-schools; however particular difficulties are highlighted for the development of friendships with TD peers.

There is evidence of a high incidence of language difficulties (LD) amongst boys with externalising behaviour (EB); however we still have little understanding about why they co-occur. This 3 part study investigates aspects of this relationship framed within a biopsychosocial model and with a focus on pragmatic language skills and social cognition. Firstly, this study seeks to replicate recent research that has indicated a close association between pragmatic language skills and EB. It is the first study to consider the strength of this association while controlling for other variables known to commonly co-occur with LD and EB: aspects of the child’s ability (word decoding and nonverbal cognitive skills), and aspect of their environment (parenting stress, maternal education and family set up). Secondly, this study furthers our understanding of the social cognitive and friendship skills of boys with LD, in both areas through investigating reasons for variance in ability. A better understanding of an LD population feeds into our understanding of EB due to the high proportion of boys with EB who have coexisting LD. Thirdly, this study measures social cognition of boys EB while accounting for the role of LD, thus investigating whether difficulty with these tests is associated with the high rate of LD in this population. Previous studies have not adequately considered this. Method: Boys aged 8 to 11 years receiving additional support in school were assessed for LD and EB and two groups (not mutually exclusive) were identified: boys with LD (n=31) and boys with EB (n=35). A control group of typically developing boys matched for age and SES were also identified (n=42). For part one, participants completed assessments of language skills, word decoding and non-verbal cognitive ability. Teachers completed a checklist to provide a measure of pragmatic language skills. Parents completed questionnaires to provide measures of parenting stress, family set-up and maternal education. For the second and third part of the study participants’ social cognition was assessed and parent and teachers completed a checklist for measurement of emotional and behavioural difficulties including friendship skills. Results and discussion: In the first part of this study, all variables measured were found to be significantly associated with EB, as would be expected within a biopsychosocial model in which many factors interact with each other in the development of EB. However, particularly close associations were found between pragmatic language skills and EB (replicating previous research in this area), followed by language skills. This indicates a close and specific association between communication skills and EB, even when other closely associated variables are accounted for. In part two, amongst boys with LD, different social cognition assessments were found to be associated with different aspects of communication skills. One was most closely associated with structural (particularly expressive) language and the other two with pragmatic language. This indicates that they are tapping different constructs and highlights the difficulty using a proxy to give an indicator of social cognition; it is not easy to assess. Variability in friendship skills of boys with LD was not associated with any aspect of communication skills. Significant correlations were found with two of the social cognition test scores only. This is at variance with research indicating a link between friendship and receptive language skills. In part 3, the EB group scored significantly lower than the Control group in tests of social cognition, however EB was not found to be linked with social cognition score. Only boys with LD (with or without EB) scored significantly lower than the Control group. This has implications for previous research into the social cognition of boys with EB which has not fully considered the high proportion with LD and the extent this may be contributing to their low social cognition scores. Implications for practice and future research are discussed.

This study investigated verbal pragmatic skills in Saudi Arabian children with attention deficit hyperactivity disorder (ADHD). It examined quantitatively the verbal output, turns, topic related skills, and interlocutor impact in the children with ADHD compared to age-matched typically developing (TD) children. Also, a qualitative approach was used to investigate the mother-child interaction in children with ADHD compared to TD children with respect to conversational contributions and repair by the mother and the complexity of responses from the child. Another goal of the study was developing an audio-visual language sample database for Saudi Arabian Arabic speaking children. The participants were twenty 4-5 year old Saudi boys. Ten were typically developing and ten had a diagnosis of ADHD. A 30 minute sample of speech during free play was collected from each child in conversation with an unfamiliar adult interlocutor and a 15 minute sample of speech was collected during free play with a familiar interlocutor (the mother). All sessions were recorded on DVD using two video cameras. Transcription and coding systems were used to analyze the data. Comparisons were made between the TD children and the children with ADHD using quantitative and qualitative techniques. The results of the quantitative study showed that children with ADHD have a reduced verbal output with respect to total number of words, total number of verbal turns and average number of words per turn compared to typically developing children of similar age. Also, participants with ADHD showed a significantly higher topic initiation to topic maintenance ratio compared to TD participants in the sessions with the unfamiliar interlocutor. No significant effect of interlocutor was found. The results of the qualitative study revealed that verbal skills are more challenging for children with ADHD relative to their unaffected peers which is presented by more frequent “no verbal response” than TD participants and use of more single word productions during their interactions with FI. However the incidence of “mazes” did not differentiate the children with ADHD from TD children. The mothers of children with ADHD were found to be more directive in conversation, to use "what" and "yes/no" questions more frequently and they had a greater tendency to use non-verbal cues. The differences were interpreted as evidence of the negative effect of the core behavioural characteristics of ADHD on verbal pragmatic skills and the presence of weak discourse skills in children with ADHD compared to TD age-matched children. The results also reveal the importance of investigating mother-child interaction variables in an attempt to understand the effect of parental style on the verbal skills of the children with ADHD. We have at this stage no means of telling whether the reduced verbal productivity is merely a by-product of non-linguistic core behavioural characteristics of this disorder or whether it stems from a core linguistic pragmatic deficit which is (or can be) an integral part of the disorder itself. The clinical implications are that very careful attention is needed in assessing children with ADHD to determine the nature and the extent of their language-use difficulties. Language-use difficulties exhibited by children with ADHD may be associated with a lack of social competence, which will be reflected in their conversational skills. The analysis provides the speech language pathologist with information that could assist them, by giving them a better understanding of children with ADHD, which would lead to more comprehensive assessments and more effective intervention and parent training programs.

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