What are the adaptive origins of disgust? Evolutionary psychologists have proposed that the key functional benefit of disgust is to serve as a disease-avoidance mechanism. For example, two universal cues that elicit disgust are spoiled food and bodily secretions. This is not surprising given the potential for contracting a pathogenic infection from either of the latter two sources.
Whereas psychologists have established the behavioral and psychological responses that individuals experience upon seeing a disgust-eliciting cue, one issue that had yet to be studied is how an individual's immune system responds when visually exposed to such cues. In a forthcoming paper to be published in Psychological Science, Mark Schaller and his colleagues tackled this exact issue. They showed two groups of participants a set of neutral slides followed by either: (1) a guns slideshow consisting of photos of individuals brandishing a gun; or (2) a disease slideshow consisting of photos of individuals suffering from communicable diseases.
Blood was drawn before and after viewing the neutral slides as well as before and after viewing either one of the two other sets of photos. The goal was to measure changing levels of the proinflammatory cytokine interleukin-6 (IL-6), which is released by white blood cells as part of a concerted immunological response against various trauma and/or pathogenic infestations. The hypothesis was that changes in the levels of IL-6 would be greater subsequent to viewing the disease slide show. Here are the key results:
Pre-post % change for the guns slideshow: 6.62% increase (non-significant)
Pre-post % change for the disease slideshow: 23.62% increase (highly significant; p = .016)
When the changes in IL-6 levels associated with the two experimental conditions were compared to the corresponding changes in the levels of IL-6 of the control neutral slides, the disease slideshow yielded a significantly larger change (p = .003) than that of the guns slideshow.
The bottom line is that simply viewing photos of communicable diseases is sufficient to trigger a concerted immunological response.
Unlike many experiments in the social sciences that are filled with convoluted designs and the associated logical obfuscations, in my opinion this is a exemplary study, as it is elegant in its methodological simplicity whilst documented a novel and highly interesting finding.
Ciao for now.
Source for Images:
http://www.greenairteknowledge.com/greenair/wp-content/uploads/20...
http://www.cruxaustralisgroup.com.au/gallery/091124024556-robber_...
