UBC Theses and Dissertations

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UBC Theses and Dissertations

An examination of the influence of threat on judgments of contaminant spread Herba, Joanna Karoline


Concern about the spread of infectious agents and associated washing and avoidance behaviour vary widely across individuals. Extremes on either end of the spectrum can have negative consequences: overconcern can lead to undue distress and excessive cautionary behaviour, and underconcern can lead to the contraction and spread of disease. The purpose of this series of four studies was to examine variables that contribute to individual differences in judgments of contaminant spread. Specifically, I examined whether threat influenced judgments of spread. Studies 1 and 2 were conducted with a general (unselected) sample of participants recruited from a university campus (N = 75 and N = 77 respectively), while Studies 3 and 4 extended the research to two specific populations of interest (49 nursing students in Study 3 and 21 participants with contamination-related OCD in Study 4). Participants were randomly assigned to judge the spread of either a: threatening contaminant (disease-causing bacteria), non-threatening contaminant (harmless bacteria) or non-contaminant (vegetable juice in Study 1, yogurt containing probiotic bacteria in Studies 2, 3 and 4). To ensure participants’ safety, these substances were not actually present—rather participants were led to believe that one of these substances was placed on a cutting board and then spread to a series of objects. Findings varied depending on the specific facet of spread examined and the population under study. Among the general university sample and participants with OCD, identification as a contaminant increased judgments of physical spread, but threat did not. Among nursing students, there was a trend for threat to increase judgments of physical spread. With regard to danger along the chain of contagion, threat increased danger ratings for the general university sample and nursing students, but not for participants with OCD. Rather, the OCD group viewed danger as elevated along the chain of contagion for both contaminants. Threat also increased avoidance for the general university sample and nursing students, but not the OCD group. Participants with OCD tended to engage in high levels of avoidance regardless of which condition they were in. Discussion focuses on the studies’ implications for understanding fear of contamination and hygiene behaviour.

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