Moral judgment modulation by disgust priming via altered fronto-temporal functional connectivity

Abstract

Moral judgments are not just the product of conscious reasoning, but also involve the integration of social and emotional information. Irrelevant disgust stimuli modulate moral judgments, with individual sensitivity determining the direction and size of effects across both hypothetical and incentive-compatible experimental designs. We investigated the neural circuitry underlying this modulation using fMRI in 19 individuals performing a moral judgment task with subliminal priming of disgust facial expressions. Our results indicate that individual changes in moral acceptability due to priming covaried with individual differences in activation within the dorsomedial prefrontal cortex (dmPFC). Further, whole-brain analyses identified changes in functional connectivity between the dmPFC and the temporal-parietal junction (TPJ). High sensitivity individuals showed enhanced functional connectivity between the TPJ and dmPFC, corresponding with deactivation in the dmPFC, and rating the moral dilemmas as more acceptable. Low sensitivity individuals showed the opposite pattern of results. Post-hoc, these findings replicated in the dorsal anterior cingulate cortex (daMCC), an adjacent region implicated in converting between objective and subjective valuation. This suggests a specific computational mechanism – that disgust stimuli modulate moral judgments by altering the integration of social information to determine the subjective valuation of the considered moral actions.

Free will without consciousness?

“…In consumer studies, people can typically be biased toward a certain brand or alternative, but only when deprived (e.g., [65][66][67]). Some reported subliminal (and typically small) effects in the political domain: national flags led participants to vote for more central parties [68], pro-social word primes increased donations by socially oriented participants [69], disgusting faces reduced moral ratings of utilitarian decisions [70], and direct-gaze faces primes affected behavior in prisoner's dilemma games [71].…”

Effects of Core Disgust and Moral Disgust on Moral Judgment: An Event-Related Potential Study

“…Purity and non-purity moral processing would induce different ERP components, especially some later ERP components, such as the N450 and LPP, representing conflict detection and resolution ( McCleery et al, 2011 ), might help distinguish them. Additionally, according to the previous studies and models ( Lim et al, 2017 ), disgust can affect moral judgments; we hypothesized that, compared to neutral priming, both moral and core types of disgust priming can induce N2, P2, frontal LPP, and parietal LPP components in moral judgment.…”

“…As a basic emotion, disgust has received particular attention for its putative role in moral judgment ( Landy and Goodwin, 2015 ). Researchers proposed that both unconscious and conscious types of disgust or disgust-induced stimulus activation can change moral judgments ( Lim et al, 2017 ). Many theorists of morality have also considered how disgust might engage in moral judgment.…”

“… Pizarro et al (2011) proposed the amplification hypothesis, which emphasizes that the experience of disgust amplifies moral evaluations; it makes wrong things seem even more wrong ( Pizarro et al, 2011 ). Some studies have demonstrated that individuals induced to feel disgusted can amplify the severity of moral condemnation ( Landy and Goodwin, 2015 ; Lim et al, 2017 ). Other studies concerned with correlational results, which are consistent with a causal link between disgust and moral judgment.…”

“…From the behavioral studies above, it is still a question of whether the amplification effect exists. While recent imaging and neuropsychological studies have appeared to support that emotions can modulate the processes of moral judgments and play an essential role ( Baez et al, 2017 ), until now, only one fMRI study initiated to investigate the neural mechanism underlying moral judgment by disgust priming and found that enhanced functional connectivity between the TPJ and dorsal medial prefrontal cortex (dmPFC), which indicated that disgust stimuli modulate moral judgment by altering the integration of moral reasoning and social information ( Lim et al, 2017 ). However, imaging data are insufficient to determine whether the disgust priming effect is activated in which phase of moral cognition and whether the disgust priming effect occurs upstream, downstream, or even in parallel to moral processing ( Huebner, 2013 ).…”