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Long before the publication of Darwin's theory of evolution by natural selection and Mendel's work on genes, horses were being selectively bred for improved racing performance. This resulted in the creation of a highly specialised breed of racing horse, known as the thoroughbred. Throughout the 19th century the winning times of the most elite thoroughbred races in Great Britain declined, suggesting genetic evolution of faster speed was ongoing in response to selective breeding. However, several studies have reported a slowing of the rate of improvement since early in the 20th century, leading to a consensus amongst scientists and industry experts that thoroughbred speed has reached a selection limit. The broad aims of my PhD thesis are to understand the genetic basis of variation in racehorse speed, and in doing so, to determine if thoroughbreds have indeed reached a genetic limit for how fast they can run. If so, what is constraining further improvement? Moreover, can a better understanding of the factors that determine the rate of improvement in thoroughbred speed allow us to design breeding programmes that would overcome this supposed limit? To do this, I apply quantitative genetic tools, developed for improving livestock since the mid-19th century but largely passed over by thoroughbred breeders, to a vast pedigreed dataset of thoroughbred performances in Great Britain. Firstly, addressing limitations of previous studies, I set out to characterise more accurately the current and historical rate of phenotypic improvement in thoroughbred speed. Secondly, I apply quantitative genetic analysis to determine the extent of heritable variation for this trait and assess whether phenotypic rates of improvement in speed - if still ongoing - are underpinned by a genetic response to selection. Next, I investigate the possibility that maternal and/or paternal age at conception may affect offspring racehorse speed and examine whether parental identity is an important source of variation in offspring performance. If so, is there any genetic basis of maternal or paternal variation identified, and what are the implications for selection response? Finally, in an essay I explore the history of equine (and jockey) welfare concerns in the sport, and consider the role quantitative genetics could play in reducing equine injury susceptibility alongside improving performance. Lastly, I discuss my findings and consider future directions for this research.

Digital integrated circuits were initially developed to meet the critical needs of aerospace applications for reduced weight and power consumption and increased reliability. Because of the continued refinement of manufacturing processes and techniques, integrated circuits are now available at prices which make their usage very attractive even in the most competitive segments of the commercial and industrial systems field. By examining specification-sheets for various digital integrated circuits that have been marketed, one can deduce that many have been designed to meet particular requirements, and that in the effort to achieve the ultimate in one characteristic, one or more of the other performance characteristics have been sacrificed. For example, circuits which have been designed for low power consumption often exhibit long propagation delays, and conversely those that were designed for primarily for high speed, consume the most power. Other characteristics such as noise margin, and production yield are important design considerations. This study is concerned with the use of integrated logic gates as the active devices in sinusoidal oscillators. Most of them are relaxation type oscillators, and are used as square wave generators for clock pulse generation. In addition to the basic gate circuits, some frequency-determining components are used, such as crystals, resistors, capacitors, and inductors. Gate oscillators without any external passive components have also been developed.

When people first encounter a potential partner, they derive a wealth of objective and subjective impressions simply from their faces (e.g., age, gender, attractiveness, trustworthiness). Facial first impressions are consequential, for instance, impacting on decisions to approach a potential partner. Hence, it is relevant to have a solid theoretical understanding of how first impressions relate to ideal partner preferences, particularly as romantic relationship researchers primarily use verbal measures. The current research revealed that individuals can perceive traits and factors related to their ideal partner preferences in highly variable everyday face images, and these factors overlapped largely (although not completely) with those identified by face perception researchers. Partner preferences for face images were dominated by attractiveness-related concerns in both sexes. Further, a minimum-exposure paradigm revealed that, even in some non-romantic contexts, attractiveness is particularly salient in face images. Yet, these findings could not be attributed to an attractiveness halo effect, given that attractiveness did not dominate all non-romantic first impressions of face images (e.g., evaluations of faces in terms of occupations). There are multiple potential reasons why individuals might prioritise facial attractiveness (e.g., from an evolutionary perspective, attractiveness is a cue to fertility and resistance to environmental and genetic stressors). Of note, though, a verbal measure of partner preferences revealed that individuals prioritised warmth-trustworthiness, suggesting that face images and verbal measures may capture different elements of preferences. Therefore, these findings attest the relevance of using face images to complement verbal measures of partner preferences.

In cooperatively breeding societies, where individuals (termed ‘helpers’) provide care to young which are not their own, group members can vary substantially in their contributions to cooperative activities. Individuals are expected to exhibit higher levels of cooperative investment if the benefit of performing that behaviour greatly outweighs the cost of performing that behaviour. This may be achieved by directing investment towards kin (thereby maximising indirect fitness benefits) and/or attaining large direct fitness benefits. In this thesis, I explore whether direct fitness benefits shape patterns of helping behaviour in the cooperatively breeding white-browed sparrow weaver (Plocepasser mahali). White-browed sparrow weavers live in year round territorial groups with high reproductive skew, comprising a dominant pair and subordinates of both sexes. Although all group members contribute to a wide range of highly conspicuous cooperative activities, there is large inter-individual variation in investment. In chapter 2, I use simulated territorial intrusions to show that sexually-selected direct benefits shape the expression of sentinel behaviour. In chapter 4, I provide evidence that the direct benefits associated with either the pay-to-stay or social prestige hypotheses are unlikely to modulate patterns of provisioning in male white-browed sparrow weavers. Evidence of marked individual differences in contributions to offspring care in cooperative societies is also generating increased interest in the proximate causes of such variation. In chapter 5, I use within-individual measurements to demonstrate that variation in provisioning effort is not directly regulated by variation in circulating levels of prolactin (a pituitary hormone). The evidence does suggest, however, that provisioning behaviour may be induced by exceeding a threshold hormone level. Individual contributions to parental behaviours (as opposed to alloparental) may be shaped by constraints associated with life-history traits. In chapter 3, I show that parents in white-browed sparrow weaver societies perform different provisioning rates yet employ similar food allocation tactics, and that these patterns are expected in tropical living bird species. Combined, these findings provide insights into the selection pressures that may shape individual contributions to cooperative activities.

Faces provide information critical for effective social interactions. A face can be used to determine who someone is, where they are looking and how they are feeling. How these different aspects of a face are processed has proved a popular topic of research over the last 25 years. However, much of this research has focused on the perception of facial identity and as a result less is known about how facial expression is represented in the brain. For this reason, the primary aim of this thesis was to explore the neural representation of facial expression. First, this thesis investigated which regions of the brain are sensitive to expression and how these regions represent facial expression. Two regions of the brain, the posterior superior temporal sulcus (pSTS) and the amygdala, were more sensitive to changes in facial expression than identity. There was, however, a dissociation between how these regions represented information about facial expression. The pSTS was sensitive to any change in facial expression, consistent with a continuous representation of expression. In comparison, the amygdala was only sensitive to changes in expression that resulted in a change in the emotion category. This reflects a more categorical response in which expressions are assigned into discrete categories of emotion. Next, the representation of expression was further explored by asking what information from a face is used in the perception of expression. Photographic negation was used to disrupt the surface-based facial cues (i.e. pattern of light and dark across the face) while preserving the shape-based information carried by the features of the face. This manipulation had a minimal effect on judgements of expression, highlighting the important role of the shape-based information in judgements of expression. Furthermore, combining the photo negation technique with fMRI demonstrated that the representation of faces in the pSTS was predominately based on feature shape information. Finally, the influence of facial identity on the neural representation of facial expression was measured. The pSTS, but not the amygdala, was most responsive to changes in facial expression when the identity of the face remained the same. It was found that this sensitivity to facial identity in the pSTS was a result of interactions with regions thought to be involved in the processing of facial identity. In this way identity information can be used to process expression in a socially meaningful way.

Two critical issues concerning serious disorders of interpersonal behaviour following brain injury were investigated over four studies. For the first time, verbal aggression, physical aggression and inappropriate sexual behaviour were shown to be better conceptualised as distinct forms of disordered behaviour, rather than reflecting a single dimension of behavioural dyscontrol. Study 1 demonstrated the psychometric reliability and validity of the BIRT Aggression Rating Scale (BARS) – a new observational tool with which to systematically and contemporaneously record aggressive behaviours. Study 2 used data from the BARS and measures of inappropriate sexual behaviour exhibited by 152 participants with brain injury undergoing residential neurobehavioural rehabilitation. Principal component analysis revealed a clear separation between aggression and inappropriate sexual behaviour. Furthermore, a distinction between verbal and physical aggression was also justified. These results were replicated in study 3 using observed behavioural recordings on the BARS and the St Andrew’s Sexual Behaviour Assessment (SASBA) in a separate larger sample. It is recommended that these distinctions be reflected in future research. The second critical issue was addressed across the four studies and concerned the neurocognitive correlates of each type of behaviour. Males showed an increased risk for all three behaviours, while poorer verbal skills, impaired self-awareness and poorer social participation were consistently associated with both types of aggression only. Other measures of neurocognitive function and emotional status were not significant predictors within multivariate analyses. Study 4 addressed potential links to executive function in a subsample of 86 participants. Excessive rule violations on the D-KEFS Tower Test were associated with the presence of verbal aggression and inappropriate sexual behaviour. Scores on the D-KEFS Verbal Fluency Test had an unexpectedly positive relationship with the presence of all three behavioural conditions, perhaps indicating the importance of behavioural drive. The implications for clinical work and further research are discussed.