This is really cool! Researchers at Newcastle University in the UK conducted an experiment which showed that people are more honest when they feel they are being watched - even if they are not actually being watched. In the experiment, a large black and white poster depicting a person's eyes, when placed in front of an "honor system" contribution box (for the purchase of a drink), caused people to put two and a half times more money in the box than when the poster depicted flowers.
The human brain is programmed at a deep level to care about what others think of our behavior. If cues in our environment make us think we are being watched by other people, we generally will behave more "prosocially."
This is a major issue that we documented in The Visible Employee when discussing employee monitoring. We argued that for monitoring to be effective in its mission of improving information security, employees have to know about it. This flies in the face of what some IT security professionals believe. Some security people think that you can't let your "subjects" know about the ways in which you monitor them, for fear that they will find ways of circumventing the system. No go. If you want your security policies to be effective in influencing behavior, people have to know that you have and use methods of checking up on them.
Note that these ideas beg the question of the ethics of monitoring and surveillance. In the book we do not advocate a willy-nilly approach to setting up a panopticon where everyone is watched all the time. We recommend a thoughtful approach called "transparent security governance" that gets employees involved in the design and deployment of monitoring systems.