Aiming for the stomach and hitting the heart: dissociable triggers and sources for disgust reactions

Disgust reactions can be elicited using stimuli that engender orogastric rejection (e.g., pus and vomit; core disgust stimuli) but also using images of bloody injuries or medical procedures (e.g., surgeries; blood [body] boundary violation [B-BV] disgust stimuli). These two types of disgust reaction are presumed to be connected by a common evolutionary function of avoiding either food- or blood-borne contaminants. However, reactions to bloody injuries are typically conflated with reactions to the potential pain being experienced by the victim. This may explain why the two forms of "disgust", although similarly communicated (through self-report and facial expressions), evince different patterns of physiological reactivity. Therefore, we tested whether the communicative similarities and physiological dissimilarities would hold when markers of potential contamination in the latter category are removed, leaving only painful injuries that lack blood or explicit body-envelope violations. Participants viewed films that depicted imagery associated with (a) core disgust, (b) painful injuries, or (c) neutral scenes while we measured facial, cardiovascular, and gastric reactivity. Whereas communicative measures (self-report and facial muscles) suggested that participants experienced increased disgust for core disgust and painful injuries, peripheral physiology dissociated the two: core disgust decreased normal gastric activity and painful-injury disgust decelerated heart rate and increased heart rate variability. These findings suggest that expressions of disgust toward bodily injuries may reflect a fundamentally different affective response than those evoked by core disgust and that this (cardiovascularly mediated) response may in fact be more closely tied to pain perceptions (or empathy) rather than contaminant-laden stimuli.