Telling little fibs can set off whoppers

They may be considered harmless by many, but little white lies apparently condition the brain to tell bigger fibs, new research has shown.

Brain scans of people telling lies have shown it becomes easier with practice as they seem to overcome guilt pangs.

A moral "policeman" in the brain called the amygdala becomes increasingly likely to look the other way the more we lie, the study led by scientists at University College London suggests.

Researchers believe the same principle may also explain how violence can escalate, leading to horrific crimes or a willingness to inflict torture.

The team tested 80 volunteers working in pairs who were asked to guess the number of pennies in a jar. To start with, participants were told both they and their partners would secure financial rewards for accurate estimates.

The scenarios were then repeatedly changed so that, in some cases, participants benefited if they deliberately overestimated the number of pennies.

When told that lying about the amount would benefit them, volunteers initially exaggerated only slightly. This prompted a strong amygdala response.

But over several runs the exaggerations became more and more pronounced, while amygdala responses declined.

Larger drops in amygdala activity predicted bigger future lies, the study found.

Tali Sharot, an experimental psychologist at UCL, said: "When we lie for personal gain, our amygdala produces a negative feeling that limits the extent to which we are prepared to lie.

"However, this response fades as we continue to lie, and the more it falls, the bigger our lies become. This may lead to a 'slippery slope', where small acts of dishonesty escalate into significant lies."