Fessler et al. (2005)

Evidence that disgust evolved to protect from risk of disease.

Background information: Disgust, the emotion motivating avoidance of contact and refusal to eat something, is elicited by many stimuli associated with pathogen transmission, suggesting that disgust is an adaptation that serves to guard against disease. The more vulnerable the individual is to infection, the greater the importance of disease avoidance and being careful about what you eat. Therefore we would expect people with lowered immune systems to be the most sensitive to disgust and therefore the most protected from accidental infection.

Relative to later stages, the first trimester (first three months) of pregnancy involves substantial suppression of the maternal immune response, and both maternal and foetal vulnerability to pathogens are greatest during this phase; food-borne illnesses, in particular, pose a threat during the first trimester. Consistent with the notion that disgust is an adaptation that regulates disease exposure by preventing the eating of harmful food, disgust is intimately linked to nausea, a subjective state associated with a loss of appetite. Feelings of nausea are often strong in the first trimester of pregnancy.

Aim: To investigate whether disgust sensitivity is adjusted as a function of the immune system, by testing the hypothesis that disgust sensitivity varies across pregnancy in a manner that compensates for changes in the vulnerability to disease.

Method: Using a web-based survey of 496 pregnant women, with an average age of 28 years old, the researchers compared the disgust sensitivity of participants in their first trimester with those in later stages of pregnancy. 155 participants were in the first trimester, 183 in the second trimester and 158 in the third trimester. Responses from women who were in the second and third trimesters at the time of participation were pooled and compared with the responses from women who were in the first trimester.

Results: Analysis revealed that participants in the first trimester reported greater overall disgust sensitivity than did participants in the second and third trimesters, and they also experienced more nausea. A simple correlational analysis revealed that overall disgust sensitivity was positively related to the current level of nausea throughout pregnancy.

Conclusion: These results provide support forthe hypothesis that disgust sensitivity varies during pregnancy in a manner that compensates for maternal and foetal vulnerability to disease.

Evaluation:

Strengths: Although there was a correlation between disgust and nausea, the researchers also measured each independently and found that the phase of the pregnancy and feelings of nausea contributed separately to disgust sensitivity. In other words, it was possible to feel nausea without disgust and the level of disgust felt decreased considerably throughout the pregnancy. This was a methodological strength of the study.

Limitations: Self-report studies, especially a written questionnaire conducted online, are not the best ways to gain valid responses, as people often approach them thoughtlessly and in a hurry.

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