Infection, Incest, and Iniquity: Investigating the Neural Correlates of Disgust and Morality

Abstract

Disgust, an emotion related to avoiding harmful substances, has been linked to moral judgments in many behavioral studies. However, the fact that participants report feelings of disgust when thinking about feces and a heinous crime does not necessarily indicate that the same mechanisms mediate these reactions. Humans might instead have separate neural and physiological systems guiding aversive behaviors and judgments across different domains. The present interdisciplinary study used functional magnetic resonance imaging (n = 50) and behavioral assessment to investigate the biological homology of pathogen-related and moral disgust. We provide evidence that pathogen-related and sociomoral acts entrain many common as well as unique brain networks. We also investigated whether morality itself is composed of distinct neural and behavioral subdomains. We provide evidence that, despite their tendency to elicit similar ratings of moral wrongness, incestuous and nonsexual immoral acts entrain dramatically separate, while still overlapping, brain networks. These results (i) provide support for the view that the biological response of disgust is intimately tied to immorality, (ii) demonstrate that there are at least three separate domains of disgust, and (iii) suggest strongly that morality, like disgust, is not a unified psychological or neurological phenomenon.

“Yuck, you disgust me!” Affective bias against interracial couples

“…This is consistent with literature indicating that the insula is preferentially active when people experience disgust (e.g., Chen et al, 2009;Jabbi, Bastiaansen, & Keysers, 2008;Parkinson et al, 2011), particularly so when it is sex-related (e.g., Borg et al, 2008). Moreover, there were no significant within condition differences in insula activation.…”

“…The anterior insula (BA 13) is generally involved in the experience of disgust (e.g., Chen et al, 2009;Jabbi et al, 2008;Parkinson et al, 2011). Moreover, some evidence suggests that the insula is particularly sensitive to sex-related disgust (Borg et al, 2008), which is pertinent to our participants' task of viewing and judging newlywed couples. Consistent with this literature, Study 2 participants showed significantly more right insula activation while viewing images of interracial couples relative to same-race couples.…”

“…Considerable evidence indicates that the insula is preferentially active when participants experience disgust (e.g., Borg, Lieberman, & Kiehl, 2008); in fact, some evidence indicates that damage to the insula can actually impair disgust processing (Calder, Keane, Manes, Antoun, & Young, 2000). Although insula activation is not exclusively indicative of disgust (e.g., it has also been associated with empathy and uncertainty; Singer, Critchley, & Preuschoff, 2009), it is often thought of as a neural marker of disgust (Chapman & Anderson, 2012).…”

Bodily moral disgust: What it is, how it is different from anger, and why it is an unreasoned emotion.

“…For example, there are differences in the brain systems that respond to sexual and non-sexual moral norms, as well as to anger and disgust (Moll et al, 2005;Schaich Borg, Lieberman, & Kiehl, 2008). In Schaich Borg et al's (2008) research, pathogen disgust (similar to core disgust) and socio-moral disgust acts were rated as more disgusting than neutral behaviors.…”

On Disgust and Moral Judgments: A Review

“…Furthermore, both moral and physical disgust trigger shared features of the classical disgust expression (e.g., Cannon et al, 2011;Chapman et al, 2009). Lastly, evidence from neuro-scientific studies (although not reviewed here since they are outside of the three claims) suggests that both share some overlapping brain networks (e.g., Moll et al, 2005;Parkinson et al, 2011;Schaich Borg, Lieberman, & Kiehl, 2008).…”