UK researchers Melissa Bateson, Daniel Nettle, and Gilbert Roberts found that people are more likely to follow posted rules if the sign includes an image of eyes watching them. I posted this several years ago, and am wondering if any museums or zoos tried it?
I'm frequently asked for ideas on how to word "rules" signs so that visitors follow them. This innovative study, which you can find on Daniel Nettle's Web site, studied whether people were more likely to donate money to an office coffee fund if the poster design changed--from a header of flowers to human eyes. They studied several different versions of the poster, with and without eyes, and found that people were three times as likely to comply with the posted rules when eyes were present.
Images used on poster (from their paper posted online)
They are guessing that the feeling of being watched, however subtle, influences behavior. It's called "reputational concern" in behaviorist-speak. So, if you work at a zoo, and don't want people pounding on the glass at a primate exhibit, try primate eyes on the sign. In a natural history or archeology museum, try a photograph of a person's eyes that is themed to your exhibits. See their paper for more specifics.