Researchers gave a questionnaire to college students, in which they are given a scenario and asked to rate how immoral the situation is. Some students just answered the questions. Others had to do it with a secret fart canister nearby! The results? The students who had to smell farts rated scenarios as immoral more often.
The combined ratings were significantly lower -- more immoral -- when the survey was conducted in the presence of fart smell. Schnall's team says that this demonstrates that our moral judgment is affected by disgust: we're harsher in our moral judgments when we're disgusted (a post-test confirmed that those who smelled the fart spray were significantly more disgusted than the others). Interestingly, the quantity of fart spray didn't matter: despite the fact that everyone agreed that more fart spray smelled worse, the moral judgments weren't different depending on how much spray was used.
Warning: Some examples from the questionnaire may be disturbing. Link