http://www.ted.com/talks/lang/eng/dan_ariely_on_our_buggy_moral_code.html The test variables are very telling. Interesting that people exercised their own restraint in regards to their degree of cheating irrespective of the amount of reward or likelihood of getting caught.
I just realized that the moral questions raised in this video are not unique to human nature. For instance, my dog (who is otherwise very well-behaved) will sneak and steal food out of the trash when I'm not home, but will leave it untouched if he knows I'm around to catch and scold him.
Lots of other great videos on this site. Check it out!