I attend a course at Coursera by Dan Ariely on Behavior Economics, and he talks about the effect of signing an honor code. Interestingly, his experiments showed

I attend a course at Coursera by Dan Ariely on Behavior Economics, and he talks about the effect of signing an honor code. Interestingly, his experiments showed that people stopped cheating when signing a honor-code, even if no such code really existed at their university. Being reminded of moral seems to be enough. [http://www.researchgate.net/publication/228263998_The_Dishonesty_of_Honest_People_A_Theory_of_Self-Concept_Maintenance/file/32bfe50eae8e0f1554.pdf http://www.researchgate.net/publication/228263998_The_Dishon...]