A new study by Joshua Greene and Joseph Paxton investigates the mental processes behind honest behavior:

They recruited 35 people and asked them to predict the result of computerised coin-flips while sitting in an fMRI scanner. They were paid in proportion to their accuracy. In some ‘No-Opportunity trials’, they had to make their predictions beforehand, giving them no room for cheating. In other ‘Opportunity trials’, they simply had say whether they had guessed correctly after the fact, opening the door to dishonesty.

Those who were honest showed little activity in the areas of the brain which exert mental control, wheras those who were dishonest apparently strugged with the decision. The inference being that:

…honest moral decisions depend more on the absence of temptation in the first place than on people wilfully resisting these lures.

So if the honest person isn’t tempted, the question is why. Has he or she been socially conditioned such that moral behavior becomes second nature? Is the behavior in some way innate to certain personality traits?