Who benefits from a little white lie?

Telling a friend that their new mullet looks fantastic might seem like a generous move, but according to Korean researchers, that little white lie might have selfish motives.

White lies, also known as Pareto lies, are fibs where the dishonesty is thought to be mutually beneficial for the liar and others. But not much is known about the neural processes behind them.

“As Pareto lies are both self-serving and altruistic, recognising the exact mechanisms engaged from the dishonest behavior alone poses a challenge,” the researchers from Korea University write in their paper, published in the journal JNeurosci. “True motivation for dishonesty serving both self and others cannot be accurately discerned from observed behaviours.”

Instead, the team scanned the brains of fibbing participants to see whether the true motives of lies can be indicated by activity in the medial prefrontal cortex (MPFC).

The prefrontal cortex of the brain performs many of our higher-level cognitive processes, including decision-making, planning, problem-solving, self-control and long-term thinking. The MPFC is more specifically involved in computing the value of different social behaviours, with sub-regions serving a role in moral judgement and dishonest behaviour.

In the study, the team asked 43 participants to tell lies for three different purposes: to earn a reward for themselves (selfish lie), an unknown person (white/altruistic lie), or both (selfish white lie). They used functional magnetic resonance imaging (fMRI) to see what was happening in the MPFC and compare patterns of brain activity for each type of lie.

Different types of lies elicited activity in different parts of the sub-regions. For example, selfish white lies triggered greater activity in the underside and upper regions of the MPFC, while activity patterns in the underside was similar to that of selfish lies, and patterns in the upper sub-region were dissimilar to patterns observed for altruistic lies.

The results suggest that brain activity in the MPFC sub-regions could illuminate the hidden motives behind white lies, and possibly even predict when lies are selfish.

Though the sample size was small, the researchers “believe that this study will provide a novel and powerful research method and theoretical contributions to the current efforts of understanding complex motivations underlying moral behaviours”.

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