Frances Chen

Engaging in prosocial behaviour—voluntary acts to benefit others—may be effective for restoring individuals’ social connections with others. In three studies, I investigated the links between daily loneliness, social contact, and prosocial behaviour. Study 1 examined daily associations between loneliness and prosocial engagement using daily life assessments of 100 middle-aged and older adults in the community. Adults high in chronic loneliness, but not those low in chronic loneliness, exhibited decreased prosocial behaviours on days during which they reported elevated transient loneliness. The findings suggest that chronic loneliness may elicit maladaptive responses to transient loneliness by reducing prosocial engagement. Building on these findings, Studies 2 and 3 investigated whether an intervention designed to increase daily prosocial behaviour would reduce the subjective experience of loneliness and increase the objective number of social contacts among university students (Study 2) and lonely adults in the community (Study 3). In Study 2 (N = 407), the kindness intervention—compared to an active control intervention—increased daily social contact, especially with close others, and reduced daily loneliness for participants who reported high baseline loneliness. In Study 3 (N = 208), participants who completed a modified version of the same kindness intervention showed sustained daily social contact after the intervention, whereas participants who completed an active control intervention showed decreased daily social contact after the intervention. The kindness intervention also reduced daily feelings of loneliness, though not significantly more than the active control intervention. This dissertation contributes to the growing literature on the benefits of prosocial behavior by providing preliminary evidence that it may help to address social disconnection. However, further work will be needed to refine the intervention and confirm the effects documented in these initial studies.

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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.

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