Do disgusted faces change how we judge moral dilemmas?
Briefly seeing disgusted faces changed how acceptable people found sacrificing one person to save others, but whether it made them more or less accepting depended on how easily disgusted they were.
Source
Moral judgment modulation by disgust is bi-directionally moderated by individual sensitivity
Study at a glance
- Design
- Human experiment — Within-subject blocks of disgust-face vs neutral-face primes before rating 40 moral dilemmas; Experiment 1 used masked subliminal primes (two samples), Experiment 2 used consciously visible primes
- N
- Experiment 1: sample A of 23 and sample B of 28 recruited (three excluded for errors); Experiment 2: 26 participants; disgust sensitivity was measured only in sample B and Experiment 2
- Population
- Singaporean undergraduates at the National University of Singapore
- Outcome
- Rated moral acceptability of the utilitarian action in each dilemma; moderation by Disgust Scale-Revised scores; self-reported emotions
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What they did
Before each of 40 trolley-style dilemmas, participants classified the gender of a face; in one block the face was preceded by a disgusted expression and in the other by a neutral one. In Experiment 1 the emotional face flashed for just 16.66 ms between masks so it could not be consciously seen (two independent samples); in Experiment 2 it was shown openly for several seconds. Participants rated how acceptable the harmful but utilitarian action was, and most also completed a disgust sensitivity questionnaire.
What they found
Contrary to the prediction, subliminal disgust primes made people rate utilitarian actions as more acceptable on average (combined samples 2.63 vs 2.46, d = 0.53), and more dilemmas were judged acceptable (56.47% vs 49.80%). With conscious primes there was no average effect. In both experiments, however, people higher in disgust sensitivity shifted more toward acceptance under disgust primes (r = 0.47 and r = 0.43), and when sensitivity was controlled, subliminal and conscious primes did not differ. Self-reported disgust rose equally in both blocks, so the primes did not seem to work by making people feel more disgusted.
The limits
What it doesn't show
Samples were small and drawn only from Singaporean undergraduates, and the authors note the pattern needs replication in Western samples. Disgust sensitivity was measured after the task and only in some samples, and the key covariate analysis in Experiment 1 only approached significance. The study cannot identify the mechanism: the authors' idea that disgust faces act through social processing or dehumanisation is speculation. Using faces as primes means results may not generalise to disgusting smells, tastes or scenes used in other studies.
Key terms
- Utilitarian judgment
- Judging an action by its outcomes, such as accepting harm to one person to save several.
- Deontological judgment
- Judging an action by moral rules or duties, such as refusing to harm someone regardless of consequences.
- Dual-process theory of moral judgment
- The view that fast emotional intuitions and slower deliberate reasoning jointly shape moral decisions.
- Subliminal priming
- Presenting a stimulus too briefly or masked to be consciously seen, to test whether it still influences behaviour.
- Disgust sensitivity
- A stable individual tendency to react strongly to disgusting stimuli, measured here with the Disgust Scale-Revised.
- Moderator
- A variable that changes the direction or strength of the effect of one variable on another.
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Quiz yourself
On average, how did subliminal disgust primes change ratings of utilitarian actions?
Common questions
Why did disgust make people more utilitarian when earlier studies found harsher judgments?
The authors argue the direction depends on the sample's disgust sensitivity: highly sensitive people became more accepting, so samples differing in average sensitivity could produce opposite average effects.
How do we know participants didn't see the subliminal faces?
The primes lasted 16.66 ms between masks, and at debriefing no participant reported noticing them or guessed the study's purpose.
Did the disgust faces make people feel disgusted?
Not specifically: self-rated disgust rose by a similar amount in both the disgust and neutral blocks, suggesting the dilemmas themselves raised negative feelings.
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