Germs may not be the only things you're washing away at the sink.
Washing one's hands may also give the feeling of washing away your sins or cleansing a dirty conscience, reveals a new report in the journal Science.
Physical cleanliness is linked to moral or spiritual cleanliness in religions and cultures worldwide.
Scientists have finally put that concept to the test and have found that physical and moral purity are indeed psychologically intertwined -- and sometimes even interchangeable.
"Showering -- a simple everyday activity -- is linked to morality in a way we never knew," said study co-author Katie Liljenquist of Northwestern University.
Liljenquist and her colleagues were inspired to research the phenomenon of the sense of linkage between physical cleanliness and morality after remarking that movie characters almost always showered after committing a heinous crime.
"Showering can feel so good," Liljenquist said, "like it's more than something physical. We wondered if there was something more to that."
The researchers first asked a group of 60 college students to concentrate on either something ethical or unethical that they had done in the past.
Students who remembered their own unethical behavior were more likely to act as if they felt unclean.
For example, the "unethical memory" students were more likely to say that the unfinished word "W _ _ H" was "WASH" instead of "WISH."
And they were more likely to see "S _ _ P" as "SOAP" instead of "SOUP" or "STEP."
In another similar experiment, 32 other students also were asked to remember some ethical or unethical action from their past.
Each student then got a choice of two free gifts: a pencil or an antiseptic wipe.
Sixty-six percent of the students who said they had recalled an unethical memory took the antiseptic wipe, as if they wanted to wipe their hands -- and perhaps their conscience -- clean.
Only 33 percent of the students who said they had conjured up an ethical memory took the wipe.
Just like committing murder drove Lady Macbeth to wash her hands compulsively in William Shakespeare's play, unethical acts or even unethical thoughts give us "a dirty feeling. … We need to get that feeling off of us. Get that grime away," Liljenquist said.
"It's interesting that [showering or washing] can compensate for moral indiscretion," she said.
"Washing our hands can change the way we behave and the way we perceive ourselves and the world around us," said study co-author Chen-Bo Zhong, a behavioral researcher at the University of Toronto, Canada.
Bad deeds made students feel dirty, but researchers found that the reverse was also true.
Feeling dirty made students feel bad.
Students who felt physically dirty were more likely to help another student in need.
It was as if they were trying to behave morally in an effort to get physically clean, the researchers said.
In this experiment, students first remembered an unethical deed, and then either washed their hands or did not.
Finally they were asked to help out a desperate graduate student -- by volunteering for another research study without pay.
Those who had been unable to "wash their sins away" with water were more likely to volunteer to help the needy student, the study found.
Seventy-four percent of those who had not washed their hands offered to help, while only 41 percent of the participants who had washed their hands did.