“Evolution didn’t shape us to be saints, it shaped us to be adaptable,” says David DeSteno, a psychology professor at Northeastern University. Any time we humans think we can get away with something, he says, the temptation to deceive increases. In “cheating experiments” conducted in 2007-08, DeSteno and collaborator Piercarlo Valdesolo found that 90 percent of subjects will cheat if they think they’re doing it anonymously, won’t be caught, and are certain their misdeed won’t seriously hurt anyone. The vast majority of subjects “know the action was wrong but will create a story to justify it — to make themselves appear, at least to themselves, to be a good person,” he explains. “We have a built-in propensity to rationalize.”