Practicing Moral Hygiene

By Ben Harder
Special to The Washington Post
Tuesday, October 10, 2006

After she and her husband staged a cold-blooded murder, Lady Macbeth became famously obsessed with washing her hands. Pontius Pilate cleansed his paws, too, even as he sentenced Jesus.

Perhaps it's no coincidence that a guilty conscience seeks hygienic hands. The "Macbeth effect" can be seen in everyday Americans, too, said Chen-Bo Zhong.

"When people feel morally challenged, they feel literally as if they are dirty," said Zhong, a behavioral researcher at the University of Toronto.

In a recent study, he and Katie Liljenquist of Northwestern University found that college students, after contemplating old misdeeds, tend to dwell on thoughts of cleaning. And those who get a chance to wash up act as if they have been relieved of guilt.

The researchers undertook the study because several observations about washing, including how refreshing it can be to take a shower, intrigued them. Cultural phenomena also stoked their curiosity.

"All of the major religions of the world incorporate physical cleansing at the core of their religious ceremonies," he noted. "To approach God, you have to cleanse yourself physically."

And diverse tongues describe grubbiness and moral corruption in analogous terms, added Zhong, whose first language is Mandarin. "In Chinese, we describe a person who steals as 'a pair of dirty hands,' " he said.

A deep psychological link between hygiene and moral purity could explain the similarities across cultures, Zhong said.

Jonathan Haidt, a social psychologist at the University of Virginia, thinks it's all part of our evolutionary heritage. He theorizes that our ancient ancestors first developed an instinct to avoid contaminated objects, which might spread disease, and then extended the avoidance behavior to their moral lives, perhaps in order to avoid untrustworthy people.

Filthy Mind?

It wasn't until the 19th century that scientists developed germ theory, the idea that poor hygiene spreads germs and thus disease. But even the unenlightened mind develops a fundamental notion of contagion, Haidt said.

It's called disgust.

Animals don't show disgust when their food comes into contact with something that could be contaminated. Neither do infants. Toddlers don't object, for instance, to drinking a glass of juice into which they have seen a scientist dip a cockroach. (In the experiment proving that, scientists first sterilized the roach.)

But older children come to avoid foods and beverages that have contacted repugnant substances. Kids also grow to recognize, and avoid, abstract contagions. "Cooties," said Haidt, "is an invisible moral essence."

In their recent study, Zhong and Liljenquist first asked some volunteers to recall unethical behaviors in their pasts. Other students, following different instructions, recalled an instance in which they'd acted altruistically.

Through a series of experiments, the researchers then tested each group's propensity to wash their hands or to express a preference for items associated with cleanliness, including toothpaste, detergent and Windex.

In one round, for example, they asked volunteers to fill in blanks to complete words, such as W _ _ H and S _ _ P. Volunteers who'd just thought badly of their past behavior were more disposed than others to spell out WASH and SOAP rather than WISH and SOUP, the researchers reported last month in the journal Science.

In another experiment, students who had been asked to think about immoral acts tended to pick an antiseptic wipe over a pencil when offered a choice of either as a gift. Other volunteers expressed no consistent preference.

Clean and Mean?

Could a moist towelette have removed that damned spot of blood from Lady Macbeth's conscience? Probably not. After all, great Neptune's entire ocean couldn't do the trick for her husband.

But for people whose transgressions are more minor -- Zhong's volunteers owned up to lying and stealing, but not killing -- washing seemingly can substitute for atonement.

In their final experiment, Zhong and Liljenquist set out to determine how people reacted after they had been cleansed. Volunteers were seated in front of a computer and asked to type out a description of a past moral error. When done, some were offered an antiseptic wipe, ostensibly because they had just used a public keyboard. All who were given a towelette used it.

The researchers then told each person that a colleague of theirs was desperately seeking unpaid volunteers for an unrelated study. That fib was designed to determine who would donate their time for someone in need. Would being "clean" affect their altruistic behaviors?

It did, but not in the way one might expect. Seventy-five percent of those in the uncleansed group volunteered to pitch in. But only 41 percent of those who had just used a towelette were willing to do so.

Once someone has washed his hands of the matter, it seems, all bets are off. ยท

Ben Harder covers health, medicine and the environment for Science News.

© 2006 The Washington Post Company