London: Telling self-serving lies may gradually lead people to a bigger one and finally push them down a slippery slope where their brains may start to adapt to the dishonesty, making deceit look much easier, an interesting study has revealed.

The findings showed that telling small lies desensitises our brains to the associated negative emotions and may encourage us to tell bigger lies in future.

Further, amygdala -- a part of the brain associated with emotion -- was found to be most active when people first lied for their personal gain. 

The amygdala's response to lying declined with every lie while the magnitude of the lies escalated. 

Larger drops in amygdala activity predicted bigger lies in future, the researchers said.

"When we lie for personal gain, our amygdala produces a negative feeling that limits the extent to which we are prepared to lie," said Tali Sharot from University College London (UCL).

"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 more significant lies," Sharot observed.

For the study, the team included 80 volunteers who took part in a team estimation task that involved guessing the number of pennies in a jar and sending their estimates to unseen partners using a computer. 

Participants were told that aiming for the most accurate estimate would benefit them and their partner and over-estimating the amount would benefit the volunteer at their partner's expense. 

The results revealed that people started by slightly exaggerating their estimates which elicited strong amygdala responses. 

Their exaggerations escalated as the experiment went on while their amygdala responses declined.

The researchers only tested dishonesty in this experiment, but the same principle may also apply to escalations in other actions such as risk taking or violent behaviour, they stated, in the study published in the journal Nature Neuroscience.