Washington, July 14 - Is honesty or truthfulness a by-product of lack of temptation? In a recent study, Harvard psychologists looked at the brain activity of people given the chance to gain money dishonestly by lying.

The study was designed to test the 'Will' theory that postulates honesty is a by-product of active resistance to temptation, and 'Grace' theory in which honesty stems from a lack of temptation.

Using neuroimaging, the researchers found that honest people showed no additional activity when telling the truth. However, those who behaved dishonestly, even while telling the truth, showed additional activity in brain regions that involve control and attention.

The results suggest that the 'Grace' theory is true, because the honest participants did not show any additional brain activity when telling the truth.

'Being honest is not so much a matter of exercising willpower as it is being disposed to behave honestly in a more effortless kind of way,' said Joshua Greene, psychologist at Harvard University.

To prompt participants to lie, they created a cover story about the focus of their study -- paranormal ability to predict the future.