Sickness Cues and Sociality

Humans, as do other social animals, have a behavioral repertoire that acts as a first line of defense against pathogens. A key component is the ability to detect subtle perceptual cues of sick conspecifics. The present study assessed the effects of olfactory and visual sickness cues on liking, as well as potential involved mechanisms. Facial photographs and body odors were sampled from 22 donors twice, when sick (after injection with an endotoxin causing a transient inflammatory response) and when healthy. Later, 77 new participants answered questionnaires on perceived vulnerability to disease, disgust sensitivity and health anxiety. Thereafter, they were exposed to sick and healthy facial pictures and body odors in combination while disgust-related facial electromyography (EMG) was recorded and rated their liking of the person presented. Lower ratings of liking were linked to both facial and body odor sickness cues as main effects. Disgust, as measured by EMG, did not seem to be the mediating mechanism but participants who perceived themselves as more prone to disgust, as well as more vulnerable to disease, liked presented persons less. To conclude, sickness cues that have implications for human sociality appear already a few hours after the induction of systemic inflammation.