Clean People Are Less Judgmental

A vigorous hand wash or shower could cause a person to be less judgmental.

A new study, set for publication in the December issue of the journal Psychological Science, reveals that when a person feels physically clean, he or she cuts others more moral slack.

The findings add to past research that has shown a link between physical warmth and generosity as well as physical chill and social isolation. Other past research has shown that sins seem to nudge people to clean themselves, a phenomenon the researchers dubbed the "Macbeth effect" after the dramatized murderess who tried scrubbing her hands to clean off imaginary blood.

"When we exercise moral judgment, we believe we are making a conscious, rational decision, but this research shows that we are subconsciously influenced by how clean or 'pure' we feel," said lead researcher of the new study Simone Schnall, a psychologist at the University of Plymouth in England. "Take for example the situation of a jury member or voting in an election — if the jury member had washed their hands prior to delivering their verdict, they may judge the crime less harshly."

She added, "Similarly, someone may find it easier to overlook a political misdemeanor had they performed an action that made them feel 'clean' prior to casting their vote."

The results come from two experiments with university students. In the first one, 40 students had to complete 40 scrambled sentence tasks, each involving four words. By underlining any three words, a sentence could be formed. One group of students worked on sentences that included some "clean" words, such as "pure," "washed," "immaculate" and "pristine," while another group read neutral words. 

The participants then rated a series of moral dilemmas on a scale ranging from "perfectly OK" to "extremely wrong." The dilemmas included keeping money found inside a wallet, putting false information on a resume, killing a terminally ill plane crash survivor in order to avoid starvation and using a kitten for sexual arousal.

The students who read the clean-word sentences judged such transgressions to be less wrong compared with the other students in the experiment.

In the second experiment, students watched a three-minute clip from the dark drug film "Trainspotting," which had been shown to elicit feelings of disgust. Then, half of the students washed their hands while the others didn't. The students rated the same six moral vignettes as had students in the first experiment. The hand-washers gave less severe ratings to the vignettes than did those who didn't wash their hands.

Schnall said the students who had washed their hands or read about cleanliness likely misinterpreted their physically pure feelings as being about the moral vignette. Her past research showed the same link between disgust and moral judgments.

"If I feel disgusted because I sit at a dirty disgust, and I think about how wrong it is to not return a lost wallet, then I mistakenly think the feeling of disgust is about 'oh that's a disgusting thing to do,' whereas in reality it's coming from the desk," Schnall told LiveScience.

She added, "If I feel clean because I've washed my hands, I think 'well it's not such a bad thing to do,' but that's only because my physical sensation is of the sort."

She hopes to test out the finding with real-life scenarios to see how well it applies.

Jeanna Bryner
Live Science Editor-in-Chief

Jeanna served as editor-in-chief of Live Science. Previously, she was an assistant editor at Scholastic's Science World magazine. Jeanna has an English degree from Salisbury University, a master's degree in biogeochemistry and environmental sciences from the University of Maryland, and a graduate science journalism degree from New York University. She has worked as a biologist in Florida, where she monitored wetlands and did field surveys for endangered species. She also received an ocean sciences journalism fellowship from Woods Hole Oceanographic Institution.