Telling small lies desensitises your brain to the associated negative emotions and may encourage you to tell bigger lies in the future, suggests new research at University College London.

The research provides the first empirical evidence that self-serving lies gradually escalate and shows how this happens in our brains.

The team scanned volunteers' brains while they took part in tasks where they could lie for personal gain. They found that the amygdala, a part of the brain associated with emotion, was most active when people first lied for personal gain. The amygdala’s response to lying declined with every lie while the magnitude of the lies escalated.

Slippery Lies Slope

Crucially, the researchers found that larger drops in amygdala activity predicted bigger lies in future. Senior author Dr Tali Sharot, of UCL Experimental Psychology, explains:

“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 more significant lies."

The study 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. This took place in several different scenarios.

In the baseline scenario, participants were told that aiming for the most accurate estimate would benefit them and their partner.

In various other scenarios, over- or under-estimating the amount would either benefit them at their partner’s expense, benefit both of them, benefit their partner at their own expense, or only benefit one of them with no effect on the other.

Reduced Emotional Response

When over-estimating the amount would benefit the volunteer at their partner’s expense, 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.

Lead author Dr Neil Garrett said:

“It is likely the brain’s blunted response to repeated acts of dishonesty reflects a reduced emotional response to these acts. This is in line with suggestions that our amygdala signals aversion to acts that we consider wrong or immoral.

We only tested dishonesty in this experiment, but the same principle may also apply to escalations in other actions such as risk taking or violent behavior."

The work was funded by Wellcome and the Center for Advanced Hindsight.

Neil Garrett, Stephanie C Lazzaro, Dan Ariely & Tali Sharot The brain adapts to dishonesty Nature Neuroscience (2016) doi:10.1038/nn.4426

Image: Eric Imthorn CC BY

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