After the signs were posted, women opted less often for the ineffective strategy of hand rinsing--using only water and no soap--and washed with soap more often.
But the signs had no effect on men's tendencies to either wash or rinse their hands after using the restroom, Johnson and his colleagues reported last week during the Annual Meeting of the Eastern Psychological Association in Baltimore, Maryland.
"Female hand rinsing went down once the sign was placed, and their hand washing went up," Johnson said in an interview with Reuters Health.
But men, he added, "relatively stayed the same, regardless of the situation."
Johnson explained that simple signs reminding people to wash their hands may be more effective in women than in men because women have been taught from early in life to accept and follow social norms.
Seeing a sign that tells them to wash their hands may remind women that this is the socially accepted behavior, he said.
In contrast, many men may have been raised to be "more autonomous in their decision-making," to do what they want to do even if it goes against what is socially acceptable, Johnson added.
"If it's something they want to do, they're going to do it anyway," he said.
Johnson noted that the study likely overestimates how often people washed their hands because the participants knew someone else was in the restroom with them, and may have washed their hands--or pretended to have done so using hand rinsing--to avoid shame.