Doctor of Philosophy in Psychology (PhD) 
University of Bristol
Research projects that examine specific evolved human motivational systems and their implications for human social cognition and social interaction. Research projects that examine specific aspects of human social cognition and social interaction that have implications for social norms and collective beliefs.
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Close contact with loved ones is essential for both mental and physical health. Social support provided by loved ones can reduce stress, improve sleep quality, promote positive health behaviors, and increase resilience to adversity. In everyday life, however, people commonly experience periods of separation from their loved ones. Can the benefits of social support occur even when loved ones are physically distant? The study reported in Chapter 2 collected data from 96 women who were randomly assigned to smell one of three scents (their romantic partner’s, a stranger’s, or a neutral scent) and exposed to an acute social stressor (Trier Social Stress Test). Perceived stress and cortisol were measured continuously throughout the study. Perceived stress was reduced in women who were exposed to their partner’s scent. Cortisol levels were elevated in women who were exposed to a stranger’s scent. Cortisol levels were also reduced in women who were exposed to their partner’s scent, but only in a subset of women who were able to identify their partner’s scent. These results suggest that the scent of a partner improves the psychological experience of stress and improves cortisol levels in a subset of women who correctly identified the scent to be their partner’s. The study reported in Chapter 3 collected data from 155 participants who spent two nights with their partner’s scent and two nights with a control scent (order randomized). Sleep efficiency (via actigraphy) and perceived sleep quality (via self-report) were measured each night. Sleep efficiency was higher when participants were exposed to their partner’s scent. Exposure to a partner’s scent led sleep efficiency to increase by over two percent on average, an improvement similar in magnitude to the effect of melatonin on sleep. Perceived sleep quality was higher when participants believed they were smelling their partner’s scent. These results suggest that the scent of a partner improves the physiological state of sleep and that believing you are exposed to the scent of your partner improves the psychological recollection of sleep quality. This research adds to our understanding of the role of olfactory cues in the communication of social support.
According to the biological principles of life history theory, there is a fundamental trade-off between mating effort and parenting effort. The five studies reported here (N = 3,439) tested two conceptually distinct ways in which that trade-off might manifest at a psychological level of analysis. Studies 1 and 2 focus on developmental processes and individual differences in the chronic activation of the mate acquisition and parenting motivational systems. Studies 3, 4, and 5 focus on temporary activation and inhibition of the mate acquisition and parenting motivational systems. The primary results of Study 1 (n = 305) suggest that men who express a greater desire to engage in short-term mating behavior have a less intense nurturant parental response to infants; Study 2 (n = 2252) revealed similar inverse relations, this time among both men and women (as well as parents and nonparents). Study 2 additionally noted a positive correlation between short-term mating orientation and chronic protective parental tendencies. Results from Study 3 (n = 92) indicate that the temporary arousal of a parental care-giving motivational state consequently inhibits self-reported inclinations toward short-term mating; this effect was only found in women. Results from Studies 4 (n = 308) and 5 (n = 482) suggest that temporary arousal of a mate acquisition motivational state consequently inhibits self-reported tender emotional responses towards infants. No consistent sex differences were noted in this latter result. Results of Study 5 additionally suggest that the temporary arousal of a disease- and predator-avoidance motivational states consequently inhibit self-reported nurturant emotional responses towards infants as well. No consistent sex differences were noted in these effects. Taken together, the present research yields results consistent with hypothesized psychological manifestations of the mating/parenting trade-off. But the present research also yields additional results that pose a challenge to these seemingly straightforward hypotheses, suggesting that a more nuanced approach must be taken to understand how the mating/parenting trade-off might manifest psychologically.
Disease threat has posed one of the greatest threats to human survival throughout history. However, only recently has research begun to elucidate humans’ psychological, behavioral, and cultural adaptations to the threat posed by infectious disease. Across a set of empirical studies using both individuals and cultures as units of analysis, this thesis investigates the implications of disease threat for attitudes, behavior, and cultural value systems. Chapter Two reports results from an experiment which show that perceived threat of disease is linked to more sexually restrictive attitudes across three measures. These results emerged most clearly for women. Chapter Three reports results from an experiment which show that temporary disease salience leads to relatively higher behavioral and attitudinal conformity (across four diverse measures). Further analyses show that dispositional worry about disease transmission is also positively associated with conformity. Chapter Four introduces a tool—an historical disease index—for investigating the origins of cross-cultural differences. Analyses reveal that this historical disease index is a better predictor of cross-cultural differences than are contemporary measures of disease. Chapter Five reports two studies which investigate the relationship between regional variation in disease prevalence and cross-cultural variation in authoritarianism. Results from Study 1 show that country-level mean authoritarian personality scores largely mediate the previously-documented relationship between pathogen prevalence and institutional authoritarianism. Using a sample of traditional societies (from the Standard Cross-Cultural sample), results from Study 2 reveal a link between historical pathogen prevalence and twelve measures of authoritarian governance. These relationships cannot be accounted for by controlling for other threats to human welfare. Chapter Six reports results from a cross-national analysis showing that historical disease prevalence positively predicts five measures of scientific and technological innovation. This relationship cannot be accounted for by variation in wealth, education, or life expectancy. Further analyses reveal that this relationship is largely mediated by cross-national variation in individualism and collectivism. Chapter Seven considers the possible causal mechanisms by which disease influences these individual and cultural differences, and considers the implications of this set of results.
Pathogens and parasites posed significant fitness threats to our ancestors. As a consequence of these enduring threats, there are likely to have evolved a set of cognitive and affective systems designed to facilitate the behavioral avoidance of disease-causing pathogens and their carriers – including individuals who are already infected. The behavioural immune system is a suite of attentional, affective, cognitive, and behavioural responses which function to decrease the probability of contracting pathogens by activating aversive responses to indirect cues that heuristically connote the presence of infectious agents. These cues, however, are at best probabilistically related to the actual presence of pathogens, because the majority of pathogens are too small to be detected. Specific hypotheses were developed to test the influence of pathogen avoidance motivations on three aspects of social cognition. The first focuses on individual variation in concerns with pathogens. The second topic addressed pertains to the types of physical features that act as triggers to activate the behavioural immune system. The third topic addressed the extent to which pathogen avoidance mechanisms play a role in the way we learn cues which connote pathogen presence. In conclusion, this thesis provides evidence which is consistent with the operation of a psychological system which functions to prevent the transmission of infectious threats. The results reported here represent both a substantial contribution to our understanding of the subtle effects of these processes on early cognitive process and a starting point for the application of our existing knowledge to solving real world problems that have great potential for providing social and theoretical rewards.
Karmic beliefs, centered on the notion of ethical causation within and across lifetimes, appear in religious traditions and spiritual movements around the world, yet they remain an unexplored topic in psychology. I developed and validated a 16-item measure of belief in karma, and used this measure to assess the cultural distribution, cognitive content, and correlates of karmic beliefs among participants from culturally and religiously diverse backgrounds, including Canadian students (Sample 1: N = 3193, Sample 2: N = 3072) and broad national samples of adults from Canada (N = 1000) and India (N = 1006). Belief in karma showed predictable variation based on participant’s cultural (e.g., Indian) and religious (e.g., Hindu and Buddhist) background, but was also surprisingly common among people from cultural groups with no tradition of karmic beliefs (e.g., nonreligious or Christian Canadians). I demonstrate how karmic beliefs are related to, but distinct from, conceptually-similar beliefs, including belief in a just world and belief in a moralizing god. Finally, I provide preliminary evidence of intuitive conceptions of karma, and investigate how karma is related to self-reported prosocial behaviour and moral judgments. Karma is a form of supernatural justice belief, endorsed by many people from diverse cultural and religious backgrounds that lies at the intersection between beliefs about justice and morality, and beliefs about supernatural forces that shape the course of life’s events.
Raising a child requires considerable expenditures of time and energy. In order to motivate these behaviours, humans have developed a rich psychology that motivates parental caregiving. One function of the parental care motivation is to protect children from harm. Since social norms provide protection against various types of harm, a parental care mindset may lead to exaggerated negative reactions toward people who violate social norms. The current research examines both trait and state levels of parental care motivation in nonparents and measures their relationship to moral judgments of social norm violations. Study one determined that high trait levels of parental care are associated with harsher moral judgments of social norm violations. Study two replicated these trait level findings and extended them by revealing that situational state level activation of the parental mindset also caused harsher moral judgements of social norm violations. Together, this research suggests that activation of a parental mindset is possible in non-parents and has wide reaching psychological implications including the formation of moral judgments.
Previous research and theory suggest that religious salience should impact social behaviors. Therefore, it was predicted that making Christianity salient would lead to decreased promiscuity and increased valuation of children. In two experimental studies, results were inconsistent. In study 1, participants were reminded of their religious beliefs in the experimental condition before completing survey measures regarding their sexual attitudes and desire to have children. Results suggested that religious saliency decreased reports of short-term mating desire, but did not affect long-term mating desire. Attitudes towards having children remained unchanged. In study 2, participants underwent a similar manipulation to make their religious beliefs salient before evaluating online dating profiles. Participants viewed four opposite-sex profiles: two depicting a target looking for short-term mating and two looking for long-term mating. Contrary to the hypothesis, participants’ evaluations of the targets did not differ depending on the experimental condition they were in. Implications of these results are discussed.