Telling small fibs may not be as harmless as we've all been led to believe, according to a new study.
Scientists at University College London have found that carrying out small acts of deception causes the brain to become desensitised to telling bigger lies.
Through scanning the brains of 80 people who were asked to make dishonest statements, they found that the amygdala, an area of our grey matter that responds to sensory information with emotional responses, issues a weaker adverse reaction with each lie we tell.
In the study, the amygdala's declining response was so pronounced with every lie that researchers were able to accurately predict how dishonest participants would be in the next trials.
“When we lie for personal gain, our amygdala produces a negative feeling that limits the extent to which we are prepared to lie," experimental psychologist Dr Tali Sharot explains.
"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."
Commenting in the journal Nature Neuroscience, the UCL researchers said the results correspond with common situations involving deception, with everyone from tax-evaders, adulterers and sports cheats often recalling how "small acts of dishonesty snowballed over time".
The same principle "may also apply to escalations in other actions such as risk-taking or violent behaviour," lead author Dr Neil Garrett adds.
Previous studies have suggested that in the brains of psychopaths, the amygdala shows reduced activity in response to graphic images of murder scenes.