Item Open AccessAn investigation into the political psychology of attitudes towards immigration in the UK: What drives these attitudes, can they be predicted, and can they be changed?Buchanan, TeresaThis thesis investigates British attitudes towards immigration, a key issue in the 2016 EU referendum. As its primary contribution to the literature, it demonstrates that British people can become more positive about immigration after exposure to a short text. The thesis draws on literature relating to political psychology, notably as regards authoritarianism and the Dual Process Model. It touches on behavioural science, the study of individual differences (including Moral Foundations Theory, Social Dominance Theory and personality traits) and the literature on framing. In the initial pre-registered survey experiment, over 11,000 British people were exposed to short pro-immigration texts reflecting different theoretical approaches in an “intervention tournament.” The experiment showed that attitudes towards EU immigration could become more positive but failed to identify the most effective approach. A study was then carried out (total N>30,000) to investigate the underlying drivers of immigration attitudes, establishing that authoritarianism is one of the best predictors of anti-immigration attitudes in the UK. An additional literature review then considers the literature on authoritarianism, including research by Adorno et al. (1950), Allport (1954), Altemeyer (1981), and Feldman & Stenner (1997). It also discusses Social Dominance Theory (Pratto et al., 1994) in the context of the Dual Process Model (Duckitt, Sibley, 2009). The next pre-registered experiment tests how these characteristics fit together. It establishes that a sub-dimension identified as Authoritarian Aggression is of particular interest. In the final pre-registered experiment (N>9,000), texts framed to reflect authoritarian values are tested. Those exposed to an authoritarianism compatible text were significantly more positive about immigration than those exposed to a control. The thesis includes a published paper which shows how this research and its associated methodologies can be relevant in other fields and outside of the UK. A framing experiment about attitudes towards climate change was carried out in seven countries (N>14,000) in collaboration with the Foreign, Commonwealth and Development Office and the Economic and Social Research Council (ESRC). Item EmbargoGender Stereotypes and Interventions Targeting Gender StereotypesDrabot, KarlyWomen continue to be underrepresented in STEM (science, technology, engineering, and mathematics), despite scientific evidence indicating STEM aptitude is not gender differentiated. Various policy and institutional efforts have been made to improve gender diversity in STEM, yet little progress has been made. As psychological research indicates the gender gap in STEM is perpetuated by gender stereotypes, psychological interventions targeting gender stereotypes may be an important and effective approach. Thus, this doctoral research (1) examines the effectiveness of novel interventions designed to increase discernment of gender stereotypes in STEM and (2) aims to improve understanding and measurement of current gender stereotypes. Using a multi-dimensional approach to gender-STEM stereotyping, I explore my research questions through online studies (Chapters 2, 3, and 5) as well as a field study with university engineering students (Chapter 4). Specifically, I designed and evaluated theory-driven psychological interventions based on optimised debunking and inoculation theory (Chapter 2, 3, and 4). Additionally, I examined the psychological mechanisms involved in improving gender-STEM stereotype discernment (Chapter 3 and Chapter 4). Finally, I address methodological issues in gender-trait stereotype research (Chapter 5). As the conclusions we draw in research can only be as robust as the methods we use to quantify them, I aimed to improve how we conceptualise, define, and measure gender stereotyping and the psychological processes involved. To the best of my knowledge, this is the first research programme to examine inoculation theory in the context of stereotyping. Findings demonstrate some intervention effectiveness in improving discernment of gender stereotypes in STEM, but not endorsement of gender-trait stereotypes, application of gender stereotypes in decisionmaking, or gender-related attitudes. Additionally, participants in the inoculation conditions did not demonstrate levels of discernment to the same extent as those in the debunking conditions. This suggests that exposure to persuasive misinformation about gender stereotypes after the intervention treatment neutralised some of the treatment effects. However, findings show support for the cognitive and affective mechanisms theorised in inoculation theory (counterarguing and threat), but do not show clear support for the cognitive and affective mechanisms typically associated with stereotype interventions (logical thinking, perspective taking, and empathic concern). Finally, findings indicate that current conceptualisation and measurement of gender-trait stereotypes need to be updated. While the female-communal stereotype persists, it appears the male-agentic stereotype may have reduced in size and shifted in content. Implications, limitations, and suggested future directions are discussed. Item EmbargoFactors Affecting Episodic Memory DevelopmentGuo, PanyuanThe present thesis investigated the development of episodic memory through middle and late childhood, and how individual differences in health and lifestyle impact this development. The first study (Chapter 2) explored the developmental patterns of episodic memory including individual content elements (what, where and when) and integrated what-where-when (WWW) representation on British children aged 6-12. Results suggest that episodic memory continues to develop during this period, with item, spatial, temporal and WWW memory all improving relatively linearly with age. These improvements are driven by both associative binding and strategic control abilities. The second study (Chapter 3) extended this work by additionally exploring how variation in encoding and strategy use influences memory development in a slightly older age range of 8-13. While associative and strategic retrieval abilities showed improvement with age, strategic encoding ability seemed to stay relatively stable across this period of late childhood. Regarding the effect of strategy use, older children produced and noticed more strategies than younger children, but only the younger children benefitted more from noticing the strategies. The third study (Chapter 4) extended the developmental pattern to a diverse population by replicating the experiment with a sample of Chinese children aged 8-10. Results from Chapters 3 and 4 also indicate that executive function is likely to play a critical role in memory development. The fourth study (Chapter 5) investigated the influences of health and lifestyle factors, with particular emphasis on diet and physical activity, on memory development. The fifth study (Chapter 6) went further in trying to understand how cross-cultural differences in lifestyle may contribute to different patterns of memory development. Results from Chapters 5 and 6 suggest that individual differences in diet and exercise are linked with detectable differences in memory development, and that these effects may not be mediated by executive function. Collectively, the findings of this thesis shed light on a general pattern of episodic memory development over diverse populations across different cultures, and highlight the importance of a healthy lifestyle in promoting children’s cognitive and memory development. Item Open AccessCross-Modality Profiling of High-Content Microscopy Images with Deep LearningCross-Zamirski, Jan; Cross-Zamirski, Jan [0000-0002-0404-7725]In this thesis we investigate the use of deep learning for cross-modality and multi-modal image-based profiling applications. In particular, we explore the utility of the brightfield image modality with deep generative models, and also propose new methods to integrate metadata labels freely obtained in high-content screening into deep learning architectures. The use of automated microscopy in high-content phenotypic screening of cells treated with compounds or genetic perturbations produces a large amount of high-dimensional data. One example which we focus on in this thesis is Cell Painting, a standardized pipeline used to capture rich cell morphology. Typically, fluorescent stained images are the focus of image-based profiling, where the aim is to extract meaningful features from the images which can be used to represent the biology of the cells, and compare the effects of the treatments. Image-based profiling is central to screening in drug discovery, and is used to guide the selection of drug candidates to take to clinical trials. With an abundance of large databases of high-dimensional images, deep learning for image-based profiling has risen as its own sub-field, and there are now entire drug discovery pipelines selecting drugs to take to clinical trials built upon deep learning foundations. This is possible due to advances in deep learning in computer vision. In this thesis we explore and adapt recent and powerful deep learning approaches including the generative adversarial network, self-supervised vision transformers, and the diffusion denoising probabilistic model. A major challenge in this space is to use state-of-the-art frameworks from computer vision in a way which is sensitive to the challenges of drug discovery. Image-based profiling, and particularly deep learning in image-based profiling, is a new and maturing field. In this thesis we tackle the unaddressed challenge of incorporating the cheaper, easier to obtain but classically less informative brightfield modality, as well as using underutilised but freely available metadata alongside the images to guide the training of deep neural networks. As we are working in interdisciplinary science, we do this while making models which are visually interpretable to the many people working in drug discovery who are not familiar with, or potentially sceptical of deep learning. This thesis presents the first study to predict all five fluorescent Cell Painting channels from brightfield images. We explore the potential, benefits and limitations of this new approach. Next, we introduce a weakly-self supervised learning framework to learn feature representations which are guided by informative metadata. Finally, we present the first study to use a diffusion model with high-content microscopy images. We generate entire plates of synthetic Cell Painting images of exceptional image quality to make predictions about the information these models are capable of capturing, and investigate if this can also be guided by labels. Item Open AccessNeural and Behavioural Effects of Bilingualism on Selective AttentionPhelps, JacquelineBilingualism has been shown to modulate the neural mechanisms of selective attention, with differences between monolinguals and bilinguals observed even when they display equivalent behavioural performance in a selective attention task. This suggests that the crucial consequence of learning and using multiple languages might be that it triggers neuroplastic adaptation that allows bilinguals to achieve optimal performance under increased processing demands. This functional plasticity yielding equivalent outcomes (also known as degeneracy) is a common feature in biological systems, allowing flexible adaptation to changing environments. Yet the exact mechanism by which bilingualism affects selective attention is still not entirely clear. While the currently dominant view suggests that the need for constant management of competing languages in bilinguals increases attentional capacity; another possibility is that this language control may be drawing on the available attentional resources such that they need to be economised to support optimal task performance. Another question concerns the development of this adaptation over time, where the demands of competition and inhibition between co-activated languages might be reconfiguring the patterns of attentional processes right from the onset, such that the effects can be seen by the time children can respond to selective attention tasks. Alternatively, these modifications might have a protracted maturation dependent on the length and intensity of exposure to the demands of bilingualism, in which case they would manifest differently in adults and in children, as well as in speakers with different levels of exposure to L2. Finally, another aspect is to establish the extent to which these modifications might affect attentional processing beyond the language domain, extending to auditory processing more generally. Here I present a series of behavioural and neuroimaging experiments that address these questions. To investigate whether bilingualism enhances attentional processing or triggers redistribution of the existing capacity, I used EEG to track the neural encoding of attended continuous speech in monolingual and bilingual children aged 7-12, in the context of different types of acoustic and linguistic interference. Participants attended to a narrative in English while four different types of interference were presented to the unattended ear. The neural encoding of attended and unattended streams was assessed by reconstructing their speech envelopes from the EEG data in each condition, using the mTRF toolbox. Results showed more accurate reconstruction of the attended envelopes than ignored ones across all conditions for both bilinguals and monolinguals. Critically however, there was no evidence of enhanced attentional processing in bilinguals; instead data showed a pattern consistent with redistribution of the available capacity, economised to achieve optimal performance on the selective attention task. The follow up behavioural experiments tested the limits of this adaptation by using a dual task (dichotic listening + visual attention) to further increase processing load. The results over three experiments (on children, and adults with different levels of exposure to L2) showed consistently comparable performance on both tasks for monolingual and bilingual adults, suggesting that bilingual adaptation can accommodate high processing loads. However there were also subtle differences in performance on the secondary (visual) task between the monolingual and bilingual children, and across the two groups of bilingual adults, suggesting that maturation and exposure do exert influence on this functional adaptation. The findings of the final EEG study on auditory processing beyond language domain indicate comparable but attenuated modification of attentional processing in bilinguals, compared to the first EEG study using linguistic interference. Findings from all experiments are explored in the context of theories of selective attention and bilingualism. Item EmbargoBehavioural and Neural Investigation of the Subjective Experience of RememberingSiena, MichaelThe ability to recollect personal events in vivid multisensory detail from a first-person perspective is thought to be critical to the subjective experience of episodic memory. This PhD thesis comprises three experiments investigating these memory qualities and their parietal neural bases in different populations. The experiment presented in Chapter 2 used transcranial magnetic stimulation (TMS) in healthy younger adults and a novel associative memory task that manipulated stimulus modality to causally test whether the left angular gyrus (AnG) supports multimodal feature integration during episodic and semantic memory retrieval. Left AnG stimulation was found to selectively modulate response times in multimodal versus unimodal trials of both episodic associative recognition and semantic relatedness tasks, indicating AnG involvement in multiple forms of multimodal declarative memory retrieval. However, this stimulation effect was unexpectedly facilitatory rather than inhibitory, and no objective or subjective measures of episodic memory were modulated by AnG stimulation. The experiment in Chapter 3 investigated the parietal neuroanatomical correlates of first-person versus third-person episodic recall in normal ageing using voxel-based morphometry and a custom 3D object location memory task that manipulated visual perspective during both encoding and retrieval. Compared to healthy younger adults, older adults showed a general deficit in first-person recall of object locations, irrespective of the original encoding perspective. Third-person recall was also impaired with age to a lesser extent and only when objects were encoded from the same third-person perspective. In older adults, left AnG and precuneus grey matter volume positively correlated with the adoption of a first-person recall perspective, but not first-person recall more generally. These parietal volumes were further shown to decline with age. Finally, the experiment in Chapter 4 investigated whether individuals with self-reported mental imagery deficits (i.e., aphantasics) are impaired at first-person episodic recall. This was tested using a modified version of the task used in the previous chapter so that both object and spatial memory features, studied in first or third person, could be assessed via subjective vividness ratings and objective feature reproduction tasks. The visual perspective of spatial memory recall was additionally varied between the same and alternative studied perspectives to test whether aphantasics are impaired at manipulating visuospatial representations. Despite globally lower vividness ratings relative to controls, aphantasics unexpectedly showed no deficits in object or spatial memory in either visual perspective. Together, these results further understanding of parietal contributions to memory and suggest investigation of those with atypical imagery as a promising line of future inquiry into the factors necessary for its subjective reliving. Item Open AccessElectroencephalographic and Cognitive Underpinnings of Inhibitory Control in Obsessive-Compulsive Disorder: From Actions to ThoughtsFrota Lisboa Pereira de Souza, Ana MariaThis thesis aimed to investigate cognitive and neural underpinnings of cognitive control in obsessive-compulsive disorder (OCD), focusing on suppression of thoughts and actions, cognitive flexibility, and habitual behaviour. Four experiments addressed hypotheses that, in comparison with appropriate control groups: (i) Patients with OCD are impaired in their ability to control actions as measured by the Stop-Signal/Go No-Go task; (ii) They also present deficits in attentional set-shifting in an extra-dimensional set-shifting task; (iii) OCD is marked by difficulties in the ability to control thoughts, as demonstrated by a Retrieval-Induced Forgetting (RIF) paradigm; (iv) Deficits in inhibitory control correlate with electroencephalographic markers, especially error monitoring and action tendencies; (v) Habitual and ritualistic actions in OCD are driven by both motor deficits and intolerance of uncertainty; (vi) Learning and practising a finger tapping sequence on a smartphone application (app) can have clinical benefits as a 'habit-reversal' treatment; and (vii) Metacognitive functions such as memory confidence and vividness are impaired in OCD, prompting the need to repeat actions. The thesis is structured in seven chapters, with experiments presented in chapters 3, 4, 5 and 6. Chapter 3 reports inhibitory deficits in a large group of OCD patients, showing impairments in action cancellation in this sample. These results are discussed alongside neural EEG markers and self-report measures, highlighting roles of error monitoring and enhanced action tendencies in the maintenance of OCD symptoms. Chapter 4 presents the results of a clinical trial conducted in collaboration with the NHS Highly Specialised OCD Clinic in Hertfordshire, where patients were randomised to either Treatment as Usual (TAU), a combination of Cognitive-Behaviour Therapy (CBT) and Exposure-Response Prevention (ERP), or Habit-Reversal Treatment (HRT). The latter consisted of a mobile phone application, and participants were asked to practise sequences of finger tapping movements. Participants were assessed at 3 timepoints (Baseline, Midterm and Endpoint). Results showed that HRT was equivalent to TAU in reducing symptoms, and indeed superior at enhancing quality of life in OCD. These results are discussed alongside neural markers and cognitive deficits in inhibitory control and extra-dimensional set-shifting. Chapter 5 presents data on a second group of patients with OCD and a matched control group, aiming to further clarify neural and cognitive dynamics of inhibitory control, error monitoring, and motor learning in OCD. For that end, both patient and control group were further separated into app and no-app training, enabling assessment of how the mobile application affects healthy participants, and whether the changes in OCD symptomatology seen in Chapter 4 were related to app training or to the passage of time. Electroencephalographic and behavioural data were collected at two different timepoints, separated by a month, to parallel the previous study and allow for comparisons. Chapter 6 further investigates inhibitory control deficits in OCD in an online study with yet another group of patients and control participants. The comparison between ability to control actions, as measured by the Stop-Signal Task, and thoughts, as per the RIF paradigm, showed significant RIF effects on controls, but not on patients, suggesting impaired thought inhibition in OCD. These results are discussed alongside a metacognitive memory test, which reveals the role of memory confidence as a possible cause of repetitive actions in OCD. A final Discussion (Chapter 7) brings together the findings of this thesis and considers their implications for the neuropsychological basis of OCD and its future treatment. Item EmbargoThe role of parents in the emergence of sex differences in children’s play: Interrelations among parental attitudes, parental toy choices, and children’s toy preferences.Beneda, MartaGirls and boys tend to play with different toys. In general, girls prefer dolls, domestic toys, and beauty sets more than boys do, whereas boys prefer toy vehicles, construction toys, toy weapons, and sports-related toys more than girls do. Several mechanisms have been suggested to contribute to the development of these sex differences. Much research has focused on the role of parental socialisation finding that parents provide their sons and daughters with access to, and encourage them to play with, different toys. However, although studies consistently find evidence for this differential treatment of sons and daughters, it is unclear what factors might be influencing these parental behaviours. Moreover, although many scholars believe that parental gender-typed socialisation contributes to sex differences in toy preferences, few studies have examined the actual link between parents’ behaviours and their children’s sex-typed play. This dissertation sought to address these gaps. Specifically, it examined the role of parental attitudes in parents’ choices of gender-typed toys for their children. It also explored the link between parental provision of gender-typed toys and children’s sex-typed play. Lastly, it examined sex differences in children’s toy and play behaviours in new cultural contexts. The research was conducted online among primary caregivers of children aged between one and three years in four countries: the United Kingdom (N = 721; 695 mothers, 25 fathers, 1 other relative), Poland (N = 553; 505 mothers, 45 fathers), North Macedonia (N = 267; 250 mothers, 15 fathers, 2 other relatives), and Egypt (N = 196; 165 mothers, 27 fathers, 4 other relatives). Results indicated that parents’ egalitarian/liberal attitudes were significant negative predictors of the extent to which parents’ toy choices (real-life and hypothetical) were gender-typed. However, their predictive power was rather low, especially in the case of real-life choices. Some differences between contexts were observed. Regarding child behaviour, gender-typing in parents’ toy choices was positively predictive of children’s sex-typed toy preferences and play behaviours. The predictive power of toy choice variables was high in the case of toy preferences and low-to-moderate in the case of play behaviours. Few differences between contexts were found. Finally, in all countries, boys and girls differed significantly in their toy and play preferences. Girls had more feminine (or less masculine) toy preferences than boys did, and this effect was very large in all samples. Further, boys displayed more masculine (or less feminine) play behaviours than girls did, and this effect varied from large to very large. Theoretical and methodological implications of these results are discussed. Item Open AccessZero-Sum Mindset & Its DiscontentsAndrews Fearon, PatriciaAcross a wide range of pressing global challenges from democratic erosion, pandemics, climate change and economic development, there is an underlying psychological feature that presents a barrier to progress: zero-sum thinking. Zero-sum thinking is a tendency to perceive a situation as a zero-sum game, where for one player to win, another must lose. In a zero-sum game, winnings exist in a fixed amount. Therefore, any gain for one party must come at the expense of others, rendering mutual gain, or mutual loss, impossible. Though purely zero-sum situations are extremely rare in lived reality, zero-sum beliefs are not. That is, people often perceive relationships to be zero-sum even when they are explicitly not so. Such zero-sum beliefs undermine potential cooperation towards achieving shared goals and overcoming shared challenges. While a small, but growing, literature examines the causes and effects of zero-sum beliefs within particular situations and domains, this research investigates whether people might hold an implicit belief that relationships in general are like a zero-sum game. I propose that such a belief, which I call zero-sum mindset, predisposes one towards zero-sum thinking and its consequences across a wide variety of situations and domains. At the crossroads of social psychology, which emphasizes the “power of the situation,” and personality psychology, which emphasizes the importance of “individual differences,” this research examines individual differences in perceptions of one’s general situation. My research demonstrates that when one holds a generalized construal of social interactions as a zero-sum game, the power of the perceived zero-sum situation forms a stable pattern of perceptual tendencies, motivations, and strategies. Using a multi-method approach (including experiments, economic games, panel data, and large-scale multi-national surveys), I have examined the effects of zero-sum mindset in more than 10,000 unique participants across six countries and three continents. In the research presented here, I refine the concept and measurement of a zero-sum mindset. I also examine its breadth and stability, presenting evidence that a zero-sum mindset predicts zero-sum thinking and its cognitive and strategic corollaries across time and a variety of domains and situations. Finally, after demonstrating the consequences of the broader mindset, this research also examines the downstream effects of a zero-sum mindset on specific zero-sum beliefs that impact intragroup and intergroup relationships. Altogether, I find that zero-sum beliefs impair trust and cooperation, and motivate dominance and aggression strategies across a wide variety of situations and domains. Item EmbargoRobust time-varying functional connectivity estimation and its relevance for depressionKampman, Onno; Kampman, Onno Pepijn [0000-0001-8125-2565]This thesis investigates how to robustly estimate time-varying functional con- nectivity (TVFC), a construct in neuroimaging research that looks at changes in functional coupling (correlation between time series) between brain regions during a functional magnetic resonance imaging (fMRI) scan, and how it can be used as a lens through which to study depression as a functional disorder. Unfortunately, the field of TVFC is still riddled with uncertainty, especially regarding its estimation. This is mainly due to the absence of a ground truth. Without resolving this first, the value of any study, including this depression study, is significantly undermined and conclusions made therein less trustworthy. Therefore, I propose a novel and principled method for estimating TVFC, based on the Wishart process (WP), a covariance matrix stochastic process that has recently become computationally tractable, and introduce a comprehensive benchmarking framework based on machine learning principles to make sure it performs better than existing methods in the field. These benchmarks include simulations, subject phenotype prediction, test-retest studies, brain state analyses, external task prediction, and a range of qualitative method comparisons. Furthermore, I introduce a benchmark based on cross-validation, that can be run on any data set. The WP model is found to outperform other common estimation methods, such as sliding-windows (SW) approaches and dynamic conditional correlation (DCC). Returning to the depression study, several differences are found between depressed and healthy control cohorts. The study is run on thousands of participants from the UK Biobank, yielding unprecedented statistical power and robustness. I investigate connectivity between individual brain regions as well as functional networks (FNs). Depressed participants show decreased global connectivity, and increased connectivity instability (as measured by the temporal characteristics of estimated TVFC). By defining multiple depression phenotypes, I find that brain dynamics are affected especially when patients have been professionally diagnosed or indicated to be depressed during their fMRI scan, but were less or not at all affected based on self-reported past instances and genetic predisposition. I show that choosing a different TVFC estimation method would have changed our scientific conclusions. This sensitivity to seemingly arbitrary researcher choices highlights the need for robust method development and the importance of community-approved benchmarking. I wrap up this thesis with a discussion of results and how this style of work fits into the bigger picture of neuroscientific research, reflect on what has been learned about depression, and posit promising directions for future work. Item Open AccessNature, autism, and COVID: Exploring perceptions of nature’s relationship with wellbeing in diverse groupsFriedman, Samantha; Friedman, Samantha [0000-0002-9402-7241]The benefits of time in nature for wellbeing are numerous and well-documented. However, most of this research has focused on neurotypical individuals and was conducted prior to the Covid-19 pandemic. This thesis is comprised of three UK-based studies and has three main aims: to examine the role that nature played in supporting young children’s wellbeing during the Covid-19 pandemic; to capture the perspectives of autistic adults regarding how their relationships with nature changed during the Covid-19 pandemic and, more generally, how nature supports wellbeing across the life course; and to understand how autistic children experience nature-based learning when led by experienced practitioners amongst autistic peers. The first study, published in People and Nature, adopts a mixed-methods design to examine open-text responses gathered from 376 UK families who participated in a survey of families with young children conducted in response to the first Covid-19 lockdown in 2020. While psychological connection to nature is known to be associated with both pro-environmental behaviours and wellbeing, there is an urgent need to extend this research to consider impacts from the Covid-19 lockdown period. The aim of this study is to examine whether and how children’s connection to nature changed during this period, to identify the drivers of these changes, and to determine the links between connection to nature and child wellbeing. Qualitative content analysis and quantitative analysis yielded three main findings. First, nearly two thirds of parents reported a change (most typical, an increase) in their child’s connection to nature. Explanations for this increase included having more time, increased enjoyment of nature, and increased awareness or interest in nature. Second, the third of children whose connection to nature decreased during the pandemic displayed increased problems of wellbeing – manifest as either ‘acting out’ or sadness/anxiety. Third, an increase in connection to nature during the pandemic was more evident for children from affluent families than for their less affluent peers. While connecting to nature may be an effective means of promoting child wellbeing, the divergent findings for children from different family backgrounds indicate that efforts to enhance connection to nature should focus on the barriers experienced by children from less affluent families. Taking advantage of the unique context provided by the Covid-19 pandemic, the second study in the thesis is a qualitative survey study of 127 autistic adults in the UK. Participants were asked to report, through open-text responses, about how nature is related to their wellbeing, how the Covid-19 pandemic changed their relationship with nature, and about their childhood nature experiences. Using reflexive thematic analysis and influenced by both stress reduction theory (Ulrich, 1981) and self-determination theory (Ryan & Deci, 2000), I developed three thematic findings that were pervasive across the life course: nature doesn’t judge, nature to connect, and nature to escape. These themes illustrate the cyclical relationship that many of the autistic participants had with nature: nature was used in childhood to connect with family and friends and in adulthood for social interaction and to relate to the environment; it was also used to escape from unpleasant situations and from the frenzy of modern life. Nature might be an easier space through which to build connection because it is a less judgemental environment – that is, while other people might make nature feel inhospitable through their misunderstandings of autism, nature itself is accepting of autistic people as they are. Two of these themes, nature to connect and nature to escape, were also relevant during the Covid-19 pandemic as people connected with nature during a time of widespread disconnection and used nature to find respite from crowded homes. These results have implications for local governments designing inclusive green spaces, for practitioners who work with autistic people, and for autistic people and their families and carers who may want to seek out nature-based activities to support wellbeing. One theme from the survey study with autistic adults indicated that a lack of understanding about autism made nature experiences difficult, something that many respondents wished had been different in their childhoods. The third study, published in the Journal of Adventure Education & Outdoor Learning, expands on this and adopts a case study design to investigate the experiences of autistic children participating in Forest School at an autism specialist provision with practitioners trained in working with autistic children. Triangulating data from three months of participant observation, interviews with 10 parents, and interviews with nine autistic children and deductively guided by the framework of self-determination theory, I used reflexive thematic analysis to develop findings to reflect the experiences of these children at Forest School. I found that Forest School provided an exciting opportunity to experience freedom and autonomy while at school. Additionally, children developed relationships with others and with their physical space, used practical skills like fire-building and wood chopping, and engaged with nature, something that was not possible for some of the children at home. Despite these benefits, children’s feelings about Forest School varied with factors like mood and weather. The attitude of adults and the adherence to weekly rituals related to fire, food, and play showed a strong influence over how smoothly sessions ran. These findings should inform the training required of Forest School practitioners to ensure they are able to provide autonomy, competence, and relatedness-supportive environments for autistic learners. Taken together, these three studies provide a clearer picture of how nature can be used to support wellbeing in diverse groups. Theoretically, the findings of this thesis provide support for the extension of stress reduction theory to help explain how nature might be related to young children’s and autistic adults’ wellbeing. Additionally, the findings lend support for the application of self-determination theory to the Forest School ethos, particularly when working with autistic children. This thesis has implications for practice as well, illustrating a clear need to provide updated training about autism to nature-based practitioners who may interact with autistic children and to address the inequalities in opportunities available to connect to nature for less affluent children. Empirically, this thesis contributes much-needed evidence around the understanding of autistic experiences in nature and addresses the gap that exists at the intersection of these topics. It also capitalises on the novel context of the Covid-19 pandemic to demonstrate the beneficial relationship that nature has with child wellbeing while illustrating the decreased likelihood that children from less affluent families will experience these benefits. Item Open AccessThe Long-Term Effectiveness of Inoculation Against Misinformation: An Integrated Theory of Memory, Threat, and MotivationMaertens, Rakoen; Maertens, Rakoen [0000-0001-8507-5359]For over 60 years, inoculation theory has been a key framework to understand resistance to persuasion, yet many critical questions have remained unanswered. This dissertation aims to provide a theoretical and empirical understanding of how resistance to persuasion effects decay over time. In the context of resistance to persuasion by misinformation, I offer 10 empirical experiments that shed new light on this question, including several methodological innovations. In Chapter 2, I propose a new model that integrates memory theories with motivation theories on inoculation. In Chapters 3–6, I evaluate the long-term effectiveness of inoculation in message-based, gamified, and video-based inoculation interventions, unveiling the underlying mechanisms of decay. In Chapter 7, I address methodological issues, including the effects of repeated testing, and unstandardised items, and the development of a new misinformation susceptibility test. In summary, this thesis advances our understanding of the mechanisms of decay in resistance to persuasion, and sheds light on the role of and interplay between memory and motivation. The new memory-motivation model brings a significant advancement to the field, as it taps into the memory literature of forgetting—a domain in cognitive psychology—to shed new light on a concept in social psychology, and enables a new approach to modelling the longevity of inoculation effects. In addition, I offer novel insights into limitations with current methodological paradigms, and demonstrate how new standardised measurement tools can be developed to more accurately map inoculation effects in future research. Finally, I discuss how the findings of this dissertation can inform not only inoculation scholarship, but also intervention designers, evaluators, and policy makers, on how to address the problem of misinformation, and demonstrate how to extend the long-term effects of inoculation in applied interventions. Item Open AccessBehavioural, immunological, and neurobiological effects of early life stress in ratsDutcher, EthanEarly life stress (ELS), primarily encompassing childhood neglect and abuse, is associated with many adverse psychiatric and physical health outcomes in later life. What remains unclear, however, is precisely how these links are mediated. Answering this question is challenging, partly because there are many other exposures that may accompany childhood maltreatment or neglect, but also because there are many physical, social, and other life events that occur between childhood and adulthood which could interact with the effects of early life stress to together result in adulthood pathology. Here, I conducted a large, controlled experiment in rats that sought to isolate key behavioural, immunological, and neurobiological effects into adulthood of early life stress itself. To do this, I used the repeated maternal separation (RMS) model of chronic early life stress, and I focused particularly on those effects of possible relevance to anxiety, depression, and inflammation-related physical disease. In Chapter 3, I describe the long-term effects of RMS on commonly used measures of anxiety- and depression-like behaviour, as well as on comparatively sophisticated tasks capable of providing detailed insights into reward and punishment sensitivity, as well as attentional control. The probabilistic reversal learning task revealed long-lasting effects of RMS on the degree to which negative outcomes shaped animals’ future decisions, as well as evidence suggesting that RMS animals were comparatively inefficient at directing their attention, even where they were equally accurate. Further, RMS animals exhibited a long-lasting sensitization to later-life stress on several behavioural metrics. These effects all persisted into late adulthood despite RMS having no effects on conventional measures of anxiety- or depression-like behaviour, even in early adulthood. In Chapter 4, I present findings from my experiment and from a systematic review examining the short-term and long-term effects of RMS on cytokine levels in blood and non-blood tissue, as well as on microglial activation and density. I show that RMS causes short-term increases in pro-inflammatory signalling, but only causes long-term increases in pro-inflammatory signalling if animals are subjected to a later-life stress. Thus, I demonstrate that RMS causes a long-lasting sensitisation of the neuroimmune pathway that links stressor perception ultimately to pro-inflammatory cytokine release. However, these effects were largely limited to non-blood tissue such as brain tissue: in plasma, serum, or whole blood, studies generally found no effect of RMS on cytokine levels in the short- or long-term, even following later-life stress. In Chapter 5, I present analyses of regional brain volumes determined from 9.4 Tesla structural magnetic resonance imaging scans at three timepoints following RMS. I show that RMS had no effect on the volume of any of six regions examined at post-natal day (PND) 20 or 62, but resulted in a larger amygdala during the scan at PND 285, which occurred after 9-13 days of adult stress. Given that the PND 62 and PND 285 scans both occurred in adulthood, this suggests that RMS may have interacted with later-life stress to increase amygdala volume. In the General Discussion, I describe how these findings are concordant and together provide valuable insight into how early life stress can alter physiology and behaviour in such a way that may directly increase risk for mental and physical pathology. Item Open AccessAccuracy and Social Motivations Shape Judgements of (Mis)InformationRathje, StevenWhy do people believe in and share misinformation? Some theories focus on social identity and politically motivated reasoning, arguing that people are motivated to believe and share identity-congruent news. Other theories suggest that belief in misinformation is not shaped by motivated reasoning, but is instead shaped by other factors, such as prior knowledge, lack of reflection, or inattention to accuracy. Integrating multiple perspectives, this thesis argues that the spread of (mis)information is shaped by two (often competing) motivations: accuracy and social motivations, in combination with other factors, such as personality variables and information exposure. Through a variety of methods, including analyses of large-scale social media datasets, online experiments, network analysis, and a digital field experiment, this thesis illustrates how accuracy motivations, social motivations, and other variables shape the belief and spread of (mis)information. Chapter 2 takes a big data approach to test whether online content that fulfills political identity motivations, such as out-group derogation and in-group favoritism, tends to receive more engagement online across eight large-scale datasets containing a total of 2.7 million tweets and Facebook posts. Chapter 3 experimentally manipulates accuracy and social motivations for believing in and sharing true and false news headlines in a series of four online experiments with 3,364 participants. Chapter 4 examines partisan asymmetries in the effectiveness of a popular misinformation intervention, the accuracy nudge. Chapter 5 links survey data to the Twitter data of 2,064 participants to examine how beliefs about the COVID-19 vaccine and politics are associated with following political elites online and interacting with low-quality news sources. Finally, Chapter 6 examines how manipulating participants’ online social networks in a naturalistic setting (e.g., incentivizing people to follow and unfollow specific accounts on Twitter in a randomized controlled trial) influences beliefs about the opposing political party and the sharing of misinformation. Item Open AccessInvestigating reinforcement learning processes in depression and substance use disorder: translational, computational and neuroimaging approaches.Zuhlsdorff, Katharina; Zuhlsdorff, Katharina [0000-0002-8501-4529]Reinforcement learning (RL) is the process by which an animal utilises its previous experience to improve outcomes of future choices by maximising reward and minimising punishment. This thesis investigates how RL processes are altered in psychiatric disorders such as major depressive disorder (MDD) and substance use disorder (SUD). The neural basis underlying RL is investigated using brain neuroimaging techniques and translational approaches in both rats and humans. Given the importance of RL and implicated cognitive impairments in psychiatric disorders such as cognitive inflexibility, this PhD thesis sets out to integrate relevant computational and neurobiological substrates, an objective that hitherto has not been widely researched. Chapter 3 presents the findings of a longitudinal study to investigate the behavioural and neural consequences of early-life maternal separation in rats as a way of simulating early life stress (ELS) in humans. The question addressed was whether early stress is necessary and sufficient for the development of stress-related behaviours relevant to depression. Animals underwent behavioural testing, including probabilistic reversal learning (PRL) to assess behavioural flexibility, and sequential fMRI to evaluate resting-state functional connectivity. Computational analyses revealed differences in reward and punishment learning rates in males arising from maternal separation (MS) and adulthood stress. In contrast, MS female rats showed differences in the 'stickiness' parameter, a latent variable aligned with a loss of flexibility and habit-like behaviour. Finally, MS females and MS males have opposite directional changes in connectivity, as females show lower functional connectivity from the amygdala to the anterior cingulate cortex, infralimbic cortex and insular cortex compared to males. The subsequent chapter uses a computational approach to investigate latent vulnerability variables in cocaine addiction. A longitudinal dataset acquired in rats was analysed, which involved behavioural phenotyping for several addiction vulnerability traits, including behavioural inflexibility, together with high-resolution MRI brain scans. It was found that future drug-related compulsivity was predicted by higher values of the stickiness parameter, reflecting an increase in perseverative responding commonly found in stimulant-dependent individuals. Structurally, a positive correlation between the volume of the anterior insular cortex and a parameter relating to how subjects explore versus exploit reward options was found. The remaining results chapters involve the analysis of three datasets collected from human participants. Chapter 5 includes data from a study involving PRL run concurrently with fMRI scanning. The participants in this study included healthy controls (HCs), as well as individuals with cocaine use disorder (CUD) and gambling disorder (GD). Contrary to previously published findings, no significant differences in alpha, beta or kappa were observed between controls and the CUD group. However, in pathological gamblers, a significant increase in side stickiness was found, showing that gamblers tend to repeat responding in the same spatial location regardless of the outcome on previous trials. Neurally, there is an altered balance in the tracking of reward and punishment expected value (EV) in GD, as well as a shifted balance in processing positive and negative punishment prediction errors (PPE) in CUD. Reward EV tracking in GD involved greater activity in the middle temporal gyrus, cingulate gyrus, precuneus cortex and amygdala, whereas during punishment EV tracking there was lower activity in the postcentral gyrus, superior parietal lobule and precuneus cortex compared to HCs. In response to positive PPEs, the frontal pole, superior frontal gyrus and cingulate gyrus showed lower activity in patients with CUD than controls, but the same group showed greater activity following negative PPEs in the superior and middle frontal gyrus. Chapter 6 includes behavioural and clinical data from samples of patients with SUD and/or MDD as well as healthy individuals. The main findings of this chapter were that patients with SUD have reduced reinforcement sensitivity and increased stimulus stickiness, as do patients diagnosed with both disorders. No evidence for an association between computationally derived variables and clinical measures (e.g., the Inventory of Depressive Symptomatology – IDS) was found. The final results chapter presents a novel behavioural task that measures a different subtype of proactive cognitive flexibility, specifically, how healthy participants make decisions in the face of uncertainty and whether they shift their response when they are given the opportunity to repeat their choice following presentation of unreliable feedback. Participants changed their response more frequently following negative than positive feedback. Significant fMRI activations in the frontal pole, anterior cingulate cortex, frontal orbital cortex, and superior frontal gyrus were found when the response was changed rather than repeated. Furthermore, stronger connectivity between the anterior insula and parts of the occipital cortex was found during repeat trials. Finally, it was shown using a multivariate pattern fMRI analysis that behavioural responses on the next trial could be successfully predicted. The results in this thesis demonstrate the importance of RL in preclinical and clinical psychiatric cohorts. The parameter kappa is identified as a key behavioural marker across species. This parameter is altered as a result of ELS in rodents and can help predict rats that show high-compulsive behaviours on cocaine self-administration paradigms. In humans, kappa is affected in individuals with GD as well as SUD. Brain regions underlying RL parameters, including kappa, in both rodents and humans are identified, particularly highlighting the involvement of the cingulate gyrus in reinforcement learning across species. The results from the reversal learning task studies are then compared with findings from the behavioural and fMRI analyses of a new flexibility task, which extend our knowledge of cognitive flexibility beyond our current understanding of this construct. Item Open AccessPhysical and Social Threats Fortify Moral JudgementsHenderson, RobertMoral judgements are often believed to be firmly grounded in rational thought. However, scholars have discovered that moral considerations are responsive to individual and contextual factors, such as contamination and disease threats. Indeed, the role of disgust and disease threats on amplifying judgements of moral wrongdoing has been widely investigated. Likewise, there may be other forms of threat that similarly fortify condemnation across multiple domains of morality. To explore this possibility, I conducted three lines of research, as reported in Chapters 2 through 4 of this thesis. I hypothesized that worry about contracting an illness in the midst of an ongoing pandemic, heightened risk perception as a consequence of senescence, and the presence or prospect of social exclusion would lead individuals to rate moral transgressions as more objectionable. In Chapter 2, I examined whether individual differences in concern about the ongoing COVID-19 pandemic were associated with stricter judgements of moral wrongdoing across the five moral foundations of harm/care, fairness/reciprocity, ingroup/loyalty, authority/respect, and purity/degradation. Results showed that from March-May of 2020, individuals who were more worried about a previously unknown type of coronavirus (SARS-CoV-2) and contracting the associated COVID-19 disease were harsher in their evaluations of unrelated moral wrongdoing, relative to individuals who were less worried. Results held when controlling for political orientation, suggesting fear of illness was driving the effect, rather than ideological beliefs. Moreover, there was suggestive evidence that moral condemnation intensified across the time periods tested, perhaps as a function of prolonged exposure to the risk of contracting a potentially deadly communicable illness. Building on these findings concerning the relationship between physical threats and moral verdicts, Chapter 3 reports results from multiple large cross-sectional panel surveys, namely nine rounds European Social Survey and seven waves of the World Values Survey, which suggest that relative to younger adults, older adults hold stricter views about the moral domains of authority, purity, and fairness. Results held after controlling for political orientation and income. In a follow-up study on the online testing platform Prolific, older adults rated moral violations to be more objectionable than younger adults. This relationship between age and moral condemnation was mediated by risk perception, such that older adults reported higher sensitivity to risk across a number of domains, which in turn was associated with stricter moral judgements. In sum, findings were consistent with the hypothesis that threats, in this case in the form of older age and senescence, are associated with stricter moral judgements. Shifting to a different form of threat, in Chapter 4 I report findings from three studies investigating how the presence of, and sensitivity to, social exclusion is tied to stricter moral judgements. In two studies, findings revealed an indirect effect: social exclusion reduced the fundamental social needs of belonging, self-esteem, sense of control, and meaningful existence, which in turn was associated with fortified moral judgements. The indirect effect was especially pronounced for harm violations, suggesting a heightened fear of immediate personal danger in response to social exclusion. Alongside these experimental findings, a correlational study revealed a striking effect size for the relationship between social anxiety and moral condemnation, with similar associations across each of five moral content domains. Taken together, results suggest that both the experience of, and sensitivity to, social threat is associated with heightened condemnation of moral infractions. Consistent results from these three lines of work suggest that physical and social threats help to explain and predict moral judgements in response to subjective considerations of safety and well-being. Item Open AccessMemory Fidelity in Healthy Ageing and Risk for Cognitive DeclineGellersen, Helena; Gellersen, Helena [0000-0001-7544-2311]Memory decline is characteristic of cognitive ageing and it has been suggested that one important factor underpinning the magnitude of age deficits is a reduction in the fidelity or quality of perceptual and mnemonic representations. This thesis examined cognitive and neural underpinnings of individual differences in representational quality in healthy ageing and individuals at increased risk for cognitive decline to evaluate the potential of fidelity metrics for the early detection of memory impairment. Chapters 2 and 3 demonstrate that the ability to discriminate targets from highly similar lures in memory generally declines with age and in non-clinical older adults at risk for mild cognitive impairment. Importantly, the contribution of executive functions and the quality of perceptual representations to individual differences in mnemonic discrimination depends on the degree to which tasks provide retrieval support. Even when familiarity-based responding can be relied upon, memory deficits remain in both cognitively normal and at-risk older adults, suggesting that demands on complex stimulus representations are a key determinant of age-dependent memory deficits. Structural markers of medial temporal lobe regions contributed little to individual differences in mnemonic discrimination and complex perception. Chapter 4 shows that age-related declines are already present in midlife provided a task requires complex, precise stimulus representations. In contrast, ageing may spare the accessibility of coarse-grained representations, suggesting that memory decline was not due to forgetting but due to a decline in the availability of stimulus details. These age-related declines in high-quality representations were ubiquitous across tasks of perception, short- term and long-term memory. Chapters 5 and 6 tested whether tasks of mnemonic discrimination of highly similar objects and precision for object-location relational binding are sensitive to risk for Alzheimer’s disease and resilience against memory decline. Neither family history nor genetic risk for late-onset Alzheimer’s disease were associated with a decline in representational fidelity among cognitively unimpaired middle-aged and older adults. Cognitive reserve as measured based on a socially engaged and cognitively active lifestyle was associated with better long- term memory regardless of demands on representational quality. These findings demonstrate that ageing is associated with cognitive decline in any task that indexes the fidelity of complex stimulus representations. This reduction in representational quality is already present at midlife. The results also underscore the utility of representational fidelity measures for future investigations into individual differences in memory decline in both healthy and at-risk ageing. Item EmbargoPlacing Psychology: A Psychometric and Econometric Approach to Understanding Spatial Variation in Personality and its Consequential OutcomesGvirtz, AndrésPsychology - and life - do not happen in a vacuum. Every behaviour we study happens in a political, economic, socio-cultural, and physical context that is shaped by geography. Put differently: where we are matters for who we are, whom we meet and whom we identify with. Based on this premise, the geo-psychological literature investigates the composition, causes and consequences of spatial variation in personality. The research presented in this thesis aims to better understand our behaviour by adopting a lens that incorporates information on who we are and where we are. After giving a general introduction in Chapter 1, I will look at methodological barriers hindering the wider adoption of geo-psychological approaches, especially regarding data access and data processing. A novel crosswalk that can alleviate this problem is introduced in Chapter 2. In addition to providing a theoretical framework of how methodological barriers can be overcome, the crosswalk presents a practical tool that allows psychologists, as well as researchers from other disciplines, such as economics and sociology, to merge the personality data effortlessly into their existing datasets. Next, two geo-psychological applications in the health sector are introduced, which are based on the Big Five personality construct (Chapter 3-4): Chapter 3 adopts a psycho-social model to investigate spatial prescription patterns by analysing England’s largest personality survey and 4.1 billion general, 95 million anxiety-specific, and 178 million depression-specific prescriptions issued in England between 2015 and 2019. Chapter 4 looks at 54 countries’ reactions to the COVID-19 pandemic and shows the influence of personality and government stringency on our behaviour. While the aforementioned empirical projects utilise a geo-psychological lens to understand the influential consequences of differences in Big Five personality traits, Chapter 5 looks at an alternative construct - the Schwartz Human Values. The work is of psychometric nature and shows how values develop throughout the lifespan, across three hierarchical levels. A particular focus is put on predictive power and its limits for practical applications. Chapter 6 finishes with a general discussion of my research, which highlights the interplay between who and where we are and establishes novel frameworks that can be applied in future research to push our understanding of individual differences in the context of the environment we live in. Item Open AccessEssays on resistance against persuasion: Building, strengthening, and spreading attitudinal resistance through inoculation theory.Basol, MelisaThe prevalence of misinformation is a threat to science, society, and the democratic process. Current efforts are mostly reactive and consist of predominantly legislative, algorithmic, and educational interventions. However, growing psychological research emphasises the difficulty of catching up with and undoing the harms of manipulative content once it is out, calling for pre-emptive efforts that could stop harmful information from going viral in first place. Though the efficacy of inoculation theory, often regarded as the “grandfather theory of persuasion”, has been demonstrated across varying contexts, little research exists on its efficacy against online misinformation. The aim of this doctoral research was to examine how inoculation theory may be used to combat misinformation. To do so, I sought to establish how attitudinal resistance to misinformation can be build, strengthened, and spread by designing and testing novel theory-driven interventions using randomized experiments in both the lab and the field. Across several empirical studies, results consistently suggest that generalised and gamified inoculation treatments are effective in reducing the perceived reliability of misinformation, in boosting attitudinal certainty, and in decreasing people’s willingness to share manipulative information. More specifically, in Chapter 1, I test the efficacy of “Bad News” as an inoculation treatment against common manipulation strategies and found that the intervention significantly increases people’s ability to spot misinformation techniques and boosts their level of confidence in their own (correct) judgements. These findings are further extended in Chapter 2, where I demonstrate the efficacy of a new gamified and generalised inoculation treatment within the context of end-to-end encrypted private messaging apps and extend the findings on attitude certainty by identifying it as a significant mediator for sharing intentions of misinformation– emphasising the crucial role of certainty when resisting. Additionally, Chapter 2 finds that inoculated individuals are significantly less likely to share content that includes manipulative content. Chapter 3 further replicates and builds on these findings by providing additional and longitudinal support for new gamified inoculation treatments across three different languages in the context of the COVID-19 pandemic. I evaluated a real-world intervention adopted by the UK government and World Health Organization, empirically demonstrating that it improves reliability assessments of misinformation, improves people’s certainty in their ability to spot and resist misinformation, and reduces self-reported willingness to share misinformation with others in their social network. Chapter 3 also takes a critical look at the role of apprehensive versus motivational threat, one of the theoretical tenants of inoculation theory. In Chapter 4, I explore the effects of post-inoculation talk on the inoculated participants as well as those who vicariously receive second-order inoculation treatments through talk. These findings provide novel contributions to whether it has the potential to keep up with and outpace the speed and depth at which online misinformation travels. Specifically, content analyses provide novel insights into how and when post-inoculation talk occurs and, more importantly, what it is about. Thus, this doctoral research makes novel use of post-inoculation talk by pivoting from intra-individual resistance to inter-individual resistance. By demonstrating the effectiveness of receiving vicarious inoculation treatments, this research contributes to the quest for psychological herd immunity against misinformation. In sum, this doctoral research sheds light on the antecedents that underpin the inoculation process and how resistance against misinformation can be build, strengthened, and ultimately spread from one individual to another. Item Open AccessNeuropsychological and biological mechanisms of checking in OCD and clozapine induced Schizo-OCSBiria, MarjanThe introductory Chapter 1 reviewed several possible explanations of compulsive behaviour as manifested especially in Obsessive Compulsive Disorder (OCD), and schizophrenia, following treatment with the second generation antipsychotic medication clozapine. Particular focus is placed on compulsive checking behaviours and their relationship to current theories of compulsivity based on the hypothesis of imbalance between the goal-directed and habit systems and aberrant prediction-error learning. Chapter 2 describes experimental attempts in this thesis to measure human checking behaviour in the laboratory. Initially, a previously published test of checking was employed which however failed to show significant increases in OCD. I then designed a new testing procedure to measure checking, based on perceptual decision-making under a time constraint. This was administered together with other cognitive tests to patients with OCD, clozapine treated schizophrenia patients without and with obsessive compulsive symptoms, and a healthy volunteer group. In general, there were no major differences compared to controls, although patients with schizophrenia performed worse. In a second study, contingency degradation learning and checking were measured using a second variant of the task in which there was no time constraint. However, significant increases in checking behaviour were shown in another group of OCD patients compared with healthy volunteers. In Chapter 3, after a review of previous findings in OCD using the Magnetic Resonance Spectroscopy (MRS) technique at 7T, the same participants employed in the last checking study, were subjected to MRS scans to measure GABA, Glutamate (Glu), Glutamine (Gln), and NAA in three areas of brain including the Anterior Cingulate Cortex (ACC), Supplementary Motor Area (SMA) and the Visual Cortex. The most important findings were in the ACC, where significantly higher levels of Glu and Gln and lower levels of GABA and GABA:Glu ratio were found in OCD patients compared to the healthy group. In Chapter 4, the relationship between the behavioural results from chapter 2 and the neurometabolites measured with MRS in our OCD and healthy participants in chapter 3 was examined. The major findings were: 1) Higher ACC GABA/Glu ratio was related to superior accuracy of decision-making as well as increased checking on the checking task in OCD patients. 2) Checking was negatively correlated with SMA Glu in the healthy group but not in OCD. Moreover, in a test of goal directed behaviour and habit learning based on contingency degradation, a positive relationship was evident between performance and the ACC GABA/Glu ratios in patients for full degradation of the task contingencies. A similar positive relationship was observed for healthy volunteers for GABA/Glu ratios in SMA for partial degradation of the contingencies. Chapter 5 discusses neuropsychological interpretations of our findings in relation to the symptomatology of OCD and schizophrenia, together with their implications for understanding the role of the anterior cingulate cortex in decision-making and compulsive behaviour.