While putting on my best smile, I started thinking about a session I attended at the Allied Social Science Meetings earlier in the month, where Erin Giffin gave a terrific presentation on some experimental results regarding gender differences in altruism.
In general, it seems that women are more likely than men to share resources with others in a stylized laboratory experiment, and their decisions are not strongly affected by the likelihood of public scrutiny.
Men, on the other hand, are fairly sensitive to scrutiny, and if their decisions in early rounds of a repeated experiment are open to observation, they tend to be more generous, even in later rounds where they are less likely to be observed.
This is a thought-provoking finding. I wanted to ask the waitresses if they thought the sign had a bigger effect on men than on women customers, but I was afraid this question might not be considered very nice.