Psycho boffins say that when mum told you to wash your mouth out with soap, she was right.
Apparently when we commit a bad deed, we feel a desire to clean up.
Scientists at Michigan University have published a study that proves we tend to reach for the mouthwash after swearing or being rude.
"Not only do people want to clean up after a dirty deed, they want to clean the specific body part involved," said one of the authors.
"No shit, Sherlock!" says Gloria Drainpipe, celebrated National Theatre director. "Any actress could've told you that.
"Lady Macbeth's been doing it for hundreds of years!"