Doctor of Philosophy in Psychology (PhD)
Coping with Stress: The Contribution of Cognitive Biases to Rumination
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.
Loneliness is a recognized risk factor for numerous adverse health outcomes, including early death. However, state loneliness may also be evolutionarily adaptive by signaling our social connection to others is at risk and motivating social reaffiliation. Long-term and short-term changes in vagal parasympathetic functioning may represent a mechanism by which both detrimental and beneficial effects of loneliness impact human physiology. The present study investigates the differential influences of trait loneliness and state loneliness on high-frequency heart rate variability (HF-HRV), an index of vagal parasympathetic activity. In controlled laboratory settings, HF-HRV in young women (N = 148) was monitored before, during, and after a cognitive challenge task, as well as before, during, and after an induction of state loneliness. Replicating and extending prior research, higher trait loneliness predicted blunted HF-HRV reactivity to cognitive demand, controlling for covariates. Higher trait loneliness also predicted blunted HF-HRV recovery following cognitive demand, although this appeared to be a function of initial blunted HF-HRV reactivity among the chronically lonely. Consistent with the evolutionary theory of loneliness, acute state loneliness was associated with increased HF-HRV above baseline levels, regardless of self-reported trait loneliness. During recovery from state loneliness, trait loneliness predicted change in HF-HRV, such that HF-HRV decreased in high trait-lonely women, whereas HF-HRV increased in low trait-lonely women. The current findings indicate that trait loneliness is associated with a potentially maladaptive physiological response to cognitive demand. The study also provides the first evidence of increased vagal parasympathetic activity during acute state loneliness, a potential indication of a physiological state conducive to social engagement behaviours. The findings further suggest that physiological capacity for social engagement may differ as a function of trait loneliness, immediately following an acute experience of loneliness. Finally, the utility of a robust loneliness induction paradigm developed from existing methods was demonstrated, supporting its application in future research seeking to disentangle trait and state loneliness.
It is well established that the presence of other people affects how much people eat and the types of food they choose. Past research on food choice modeling has focused on snack foods and has primarily been conducted in controlled laboratory situations. The current research examines modeling of meal choice in a real-life context across two studies. Study 1 (N = 231 café patrons) tested whether meal choice modeling occurs, whether people are aware of being influenced, and whether knowing the model affects whether modeling occurs. The lunch orders of café patrons were surreptitiously tracked and participants were recruited after they paid for their lunch. Participants were asked whether they were influenced by the prior order, and what their relationship was to the person ahead of them in line. As hypothesized, participants modeled the lunch choice of the person ordering ahead of them in line above rates expected by chance. Contrary to predictions about the role of relationship, participants did not model at different rates following a stranger compared to a non-stranger. Hypotheses about modeling awareness were supported with a significant modeling effect observed even among participants who reported that their order was not influenced by the prior order. Study 2 (N = 69 students) tested familiarity to the café or social environment as a moderator. To increase variability in familiarity with the café, participants were students brought into the café for the study. Study 2 yielded inconclusive findings, possibly due to low statistical power. This research provided evidence of meal choice modeling occurring in real-life eating situations and outside of conscious awareness - demonstrating a powerful social influence on health behaviours.