Disgust serves to defend the body from the entry of toxins and disease. Central to this function is a strong relationship with the proximate senses of smell, taste, and touch. Theory suggests that distinct and reflexive facial movements should be evoked by gustatory and olfactory disgusts, serving to impede bodily entry. While this hypothesis has received some support from facial recognition studies, whether smell and taste disgusts actually produce distinct facial responses, is unknown. Moreover, there has been no assessment of the facial response evoked by contact with disgusting objects. To address these issues, this study compared facial responses to touch, smell, and taste disgusts. Sixty-four participants were asked to touch, smell, and taste disgust-evoking and neutral control stimuli, and rate them on disgust, on two occasions-first, while they were video recorded and second, with facial electromyography (EMG) applied (measuring levator labii and corrugator supercilii activity). Videos were coded for facial expressions by humans and for facial action units (FAUs) by machines. Self-report data confirmed the disgust stimuli as highly disgusting. Comparison of the overall pattern of FAUs evoked by touch, smell, and taste disgusts, indicated two distinct facial disgusts for the proximate senses-a chemosensory and a tactile-disgust face. The nose wrinkle and upper lip raise were central to all facial disgusts, indicating their centrality to the disgust face. Several facial disgusts appear to exist, each with different functional goals.

The theory of the behavioral immune system (BIS) describes a set of behaviors that protect the individual from infectious diseases and that are motivated by disgust and the perceived vulnerability to disease. As interpersonal touch is one of the most common situations of potential transmission of infectious diseases in our everyday life, it seems likely that being touched by an apparently sick individual activates disgust. Our aim was to determine if risk of contamination from interpersonal touch alters the pleasantness of interpersonal touch and modulates facially expressed emotions. In total, 64 participants received interpersonal stroking by either a healthy or by sick-appearing experimenter. Half the strokes were performed at a slow velocity of 3 cm/s and half at a faster velocity of 30 cm/s, to modulate the degree of C-tactile fiber activation in the touch perceiver. While the experimental sickness manipulation did not influence the reported touch pleasantness, there was a tendency for a diminished expression of happiness in the slow stroking condition. In addition, the desire to clean the arm after stroking correlated positively to disgust sensitivity and to germ aversion, which is a subscale of the perceived vulnerability to disease. Contrary to previous studies, participants did not prefer the slow over the fast stroking velocity, irrespective of sickness induction. Our results lead us to assume that disgust in interpersonal touch depends especially on the touch receiver and we speculate that a rather conservative reactivity of the BIS allows for an adaptive behavioral balance in interpersonal relations. This balance may be needed to weight the risks of contamination against the benefits of interpersonal touch for social interaction.