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Psychological studies in bipolar affective disorder and analogue conditions suggest that mania may be the product of an abnormal defence against depression. In this study, currently manic bipolar individuals, currently depressed bipolar individuals, and normal controls were assessed using explicit and implicit measures of attributional style, an emotional Stroop test with euphoria-related and depression-related words and a recall measure of the selfschema. Manic individuals showed a normal self-serving bias on a version of the explicit attributional style questionnaire, attributing positive events more than negative events to self, in contrast to bipolar-depressed individuals who attributed negative events more than positive events to self. However, on an implicit test of attributional style, both manic and bipolar-depressed individuals attributed negative events more than positive events to self. Both bipolar-manic and bipolar-depressed individuals demonstrated slowed colour naming for depression-related but not euphoriarelated words on an emotional Stroop test. Manic individuals, like normal controls, endorsed primarily positive words as true to self on a self referent questionnaire, but like bipolar-depressed individuals, recalled primarily negative words in a surprise recall test afterwards. Findings from the implicit tests therefore indicate a common form of psychological organisation in manic and depressed individuals, whereas the contrasts between the scores on the implicit and explicit measures are in accord with the hypothesis of a manic-defence. Future avenues for research and implications for treatment are discussed.

A device, utilising the suction produced by a disposable syringe, was developed to restrain a range of very small organisms in flowing seawater. The technique was developed during an investigation of the swimming response of barnacle nauplii to changes in temperature. The combination of beat frequency and the proportion of time spent active was held constant for B. balanoides and B. hameri but steadily increased with temperature for C. montagui and B. amnhitrite. E. modestus showed an intermediate response. Methods for utilising video-tape recordings and a micro-impedance pneumograph for analysing limb beat activity, were developed during an investigation of the feeding behaviour of nauplii. The feeding mechanism was reappraised and an increase in the volume of water handled by the larvae noted in the presence of food organisms. This increase was shown by E. modestus nauplii in response to dissolved organic substances, indicating that the nauplii could determine when to feed, and what was edible, from the shell of dissolved material surrounding food particles. A quantitative study of the grazing of E. modestus nauplii showed that the ingestion rate of algal cells increased up to concentrations of 150 - 200 cells/ul, then remained steady. Larger algal cells were taken from algal mixtures, in preference to smaller ones. Restraint techniques and video-recordings of free-swimming cypris larvae showed them to be prodigeous swimmers, with considerable control over the direction and magnitude of the thrust produced. The close observation of larvae allowed by the restraint technique enabled mechanical stimulation of particular sense organs. The function of these organs had been interpreted from their structure by previous authors. In some instances, a mechano-receptive function was confirmed, but in others, doubt was cast. Restrained cyprids responded to complex sound fields by swimming less often. A dual mode sound chamber was used to differentiate between sound pressure and displacement, but negative results were obtained. The cyprids did, however, respond to substrate vibrations, at low frequencies, by swimming off the substrate. All the developed techniques were further employed to show that the classical copepod feeding swirls were artefacts. Temora produced'only a posteriorly flowing current for feeding and swimming, when restrained in larger volumes of seawater. The amount of water handled by Temora was also shown to increase when food algae were present.

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The unlubricated sliding wear behaviour of gas nitrided, plasma nitrided, and ferritic nitrocarburized BS970,905M39 (EN41B) steels was investigated systematically from an engineering point of view. Commercial nitriding processes were employed, and the wear studies were carried out using a pin-on-disc machine over a wide range of sliding speeds and applied loads. The worn specimens and wear debris were examined by several techniques; including optical and electron microscopy and X-ray analysis. A sharp wear rate transition between mild and severe regimes was identified by varying the load for both untreated and gas nitrided steels. The wear rate was reduced by gas nitriding by up to two orders of magnitude, depending on the sliding condition. Moreover, gas nitriding expanded the mild wear region toward higher loads and sliding speeds. In the mild regime an oxidative wear mechanism operated, contrasting with the metallic wear in the severe regime. Wear maps for untreated and gas nitrided steels have been constructed, which show the dominant regimes of the wear mechanisms. A "wear-face-limited" gas nitrided pin test showed that the benefit of the treatment was lost once the effective surface layer was completely worn away. It is suggested that hardness has a crucial role in determining the wear rate through nitrided diffusion layers. A thick and porous compound layer produced by gas nitriding showed a poor wear behaviour owing to its brittleness, while a thin nitrocarburized E-Fe3N compound layer exhibited a low wear rate. There was no significant difference between the nitride steels in terms of transition load and wear rate. However, the wear lives of the nitrided layers were dependent on their case depth. Severe wear should be avoided in engineering component design, and operating conditions should ensure that only mild wear occurs. Both the hardness profiles and the cost performance of nitriding processes should be considered in the selection of nitriding treatments.

The series of experiments reported in this thesis concern the ability to make perceptual-motor judgements of distance (Ex. 1 to Ex. 7) and size (Ex. 8). Experiments 1 and 2 indicated that visual judgements of maximum step length were effected by; distance from the site of action, the angle at which the obstacle was presented and whether monocular or binocular vision was used. This suggested that perceived maximum ability was not based on a body scaled invariant as suggested by Gibson (1979). Experiments 3 and 4 were designed to investigate the effect of altering the length of distance to-be-remembered, and compared performance across both visual and kinaesthetic conditions. The results suggested that the reproduction of distance is normally based on memory for the location of the end point, rather than the extent of the distance. No support was found for the claim that differences between the accuracy of recall of location and extent was due to the differential rehearsability of visual and kinaesthetic codes. Instead, it was proposed that changes in the procedure may have influenced performance by reducing the usefulness of a 'landmark' based form of coding in the extent trials. Experiments 5 and 6 were designed to investigate predictions arising from one of the dominant models of cross-modal performance (Connolly and Jones, 1970). Connolly and Jones's model postulated that differences between intra- and cross-modal performance could be explained in terms of the characteristics of modality specific short-term storage codes, and that translation between codes occurs prior to short-term storage. In general the results obtained were supportive of the pattern of accuracy reported by Connolly and Jones. However, the effect of delaying until the end of the retention interval knowledge of the reproduction mode was inconsistent with the model, that is, withholding information about the required reproduction mode appeared to increase the accuracy of judgements. One explanation for this effect is that pre-translated information was held in a form which was associated with high levels of both accuracy and attention. This speculative explanation was seen to have parallels with the Working Memory model (Baddeley and Hitch, 1974). Experiments 7 and 8 used an interference task paradigm to investigate whether a separate visuo-spatial store could be demonstrated to exist in relation to perceptual-motor information. The results failed to find conclusive support for such a store. The cumulative findings of Experiments 1 to 8 are discussed in relation general models of perceptual-motor performance.

Objective: It is thought that executive functions (EF) emerge as outcomes of interactions between cognitive and emotional processes. They are an integral component of the growing regulatory abilities of children and adolescents and are important for academic success, attainment of social competence, and psychological development, among others. It is essential to evaluate them during neuropsychological assessment. However, they are difficult to capture with performance-based, neuropsychological assessment tools. These were once considered ‘gold standard’ measurements of EF but have been critiqued for a number of reasons. As such, rating scales have been useful as a complementary, perhaps eventual alternative, to performance-based tests. Behavioural screeners have high replicability, making them practical for use across various populations, and to evaluate everyday behaviours. A four-factor executive function screener derived from the Behavior Assessment System for Children (BASC) was previously developed and validated in a variety of age ranges and groups (Garcia-Barrera et al., 2011). However, with the exception of children with ADHD, the effectiveness of the screener has not been examined in individuals with neurologic disorder. In this population, EF are often impaired, due to delays or disruptions in normal brain development. Given these challenges in this population, this study 1) derived a similar screener for use in adolescents with neurologic disorder, using the second edition of the BASC, and 2) evaluated it against a commonly used EF rating scale [i.e., the Behavior Rating Inventory of Executive Function (BRIEF)] as well as performance-based executive function measures. Thirdly, this study characterized the nature of EFs in this clinical population, given that EF deficits are often central characteristics in many neurological disorders. Participants and Methods: An archival analysis was conducted with 107 neurologically-affected adolescents seen for neuropsychological assessment at Queen Alexandra Centre for Children’s Health. Patients were included in the study if they gave consent, had at least low average intellectual functioning, had a BASC-2 completed by a parent, and were between the ages of 12-18 years. Confirmatory factor analysis was used to evaluate the derived screener. Bivariate correlation analyses were used to evaluate convergent validity. To characterize the nature of this sample’s EF profiles, differences among groups were measured in a profile analysis via multivariate analysis of variance. Results: The four-factor model, as measured by the BASC-2 EF screener, fit the data most optimally, indicating that the structure of EF reflects the four-factor model observed in other studies. Consistent with other studies, convergent validity was observed with the BRIEF but not the performance-based tasks. Profile analysis indicated that there were some overall differences among the neurological groups and their BASC-2 scores as well as individual differences on the various factor scores. Conclusions: These findings support the four factor model measured by the screener in adolescents with neurological disorders. Given the consistency between the factor structure in this population and previous studies measuring this screener in healthy populations, and the convergence of the screener and the BRIEF, these findings contribute to the body of literature supporting this executive functioning screener as a complement to performance-based tasks. / Graduate / 2018-09-18

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.

University and government authorities in Zimbabwe, and indeed in many African countries, have tended to downplay the presence of HIV and AIDS on university campuses. The general belief seems to be that university students’ high levels of schooling somehow protect them from HIV infection, even though existing evidence suggests otherwise. Consequently, very little is known about university students’ specific vulnerabilities to HIV infection. The few interventions that are being implemented in university campuses are often based on generic models of ‘youth sexual behaviour’ that fail to take into account the many ways that university students’ experiences are different from those of other young people. Through the use of ethnography, the thesis examines how institutional factors and ‘campus cultures’ shape students sexual behaviour at the University of Zimbabwe, as well as students’ expectations from intimate relationships and the meanings that they attach to sex, sexuality, love and romance. A key point I make throughout the thesis is that where individuals are located - both spatially and temporally - is just as important for understanding youth sexuality and the HIV epidemic as are other ‘risk’ factors, such as socio-cultural beliefs and poverty. The thesis also explores how ‘HIV risk’ is constituted, understood, deployed and avoided by university students. I argue here that ‘HIV risk’ behaviours such as transactional sex, multiple and concurrent partnerships and the non-use of condoms take on vastly different meanings when they are practiced by university students and within the context of a university campus. It is therefore incorrect to abstract ‘HIV risk’ behaviours from their immediate contexts as many interventions do. / Thesis (DPhil)--University of Pretoria, 2011. / Anthropology and Archaeology / unrestricted

Transition dairy cows are vulnerable to negative consequences of depressed feed intake due to a transient state of negative energy balance that predisposes them to disease after calving. Competition has been identified as one factor that can decrease feeding activity in mid-lactation cows, but the effects of competition on the transition cow are less well understood. The objective of this study was to test the effect of a competition on the behaviour and feed intake of transition cows. Standing behaviour, feeding behaviour and dry matter intake (DMI) was monitored from 1 wk before to 2 wk after calving for 110 Holstein dairy cows. Social behaviour was recorded in the week before calving. Cows were assigned to a competitive (2:1 cows:bin) or non-competitive (1:1 cow:bin) treatment at the start of the study. Treatment groups were balanced for parity and baseline feeding data, resulting in 8 primiparous and 10 multiparous cows per treatment. Competition dramatically increased the number of agonistic behaviours between cows at the feeder. Primiparous cows showed no change in either feeding or standing behaviour when fed in a competitive environment; however, they increased their total meal duration and within-meal intervals in the wk -1 before and wk +1 after calving. In wk -1 before calving, competitively fed multiparous cows increased the frequency of visits to the feeder but consumed less feed at each visit, resulting in decreased daily DMI. Throughout the experiment, multiparous cows fed competitively spent less time eating at each visit and ate at a faster rate, particularly during the 2 wk after calving. Multiparous cows on the competitive treatment also increased the time they spent standing (without eating) compared to cows on the non-competitive treatment. Feeding rate was negatively correlated with social status in multiparous cows. In summary, the results of this study indicate that restricting access to the feeder increases agonistic behaviours regardless of parity, and cows of different parity and social status respond differently in terms of feeding and standing behaviour. / Land and Food Systems, Faculty of / Graduate