Instead of exposing test subjects to actual sick people, psychologists at the University of British Columbia exposed their test subjects to a slide show of photos of sick people. After exposure to the slide show, they found that their test subjects' immune systems became significantly stronger than before. For comparison, they also exposed subjects to slide shows of furniture and to slide shows of guns, neither of which produced significant increases in immune system activity.
The immunes system's response to the sight of sick people may help, in part, to explain why nurses stay as healthy as they do despite their constant exposure to disease.
This study will be published by Psychological Science (preprint as PDF). You can read more about the study at Boing Boing and Psychology Today.
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