People are more likely to wash their hands in the bathroom when they feel someone else is watching them at the sink, according to a study by the London School of Hygiene & Tropical Medicine.

The study, published in October in the American Journal of Public Health, looked at responses to electronic hand-washing messages displayed in gas station toilets in the United Kingdom.

Sixteen messages, such as, "Water doesn't kill germs, soap does," were flashed onto LED screens at the entrance of the toilets. But it was "Is the person next to you washing with soap?" which seemed to prompt the largest increase in hand-washing among men and women over the no-message control group.