What Research Tells Us About the Influence of Lying on the Brain

We all do it, but now lying is a major problem these days. So why do we do it, and what's going on in the brain when we do?

Hiya!

A conversation with my dad while walking in a park when I was around seven or eight years old transformed my understanding of the world. I asked him if he saw the same shade of grass as I saw, and he responded that he didn’t know because we can never truly know for sure what it’s like behind someone else’s eyes. It never occurred to me before then that other people’s minds were different from my own.

And this is why, my dad said, telling the truth is so important. Because telling the truth builds trust, and once the trust is broken by lying, there’s no way anyone can know if you’re telling the truth, even when you are. Your word is all you have.

This is true not just with individuals and personal relationships but within society as a whole. And lately, it seems there’s been a whole lot of lying going on, far more than usual, and it’s causing social instability. There’s no use in discussing specifics. I know you’re likely well aware already.

But it makes me curious about lying. In black-and-white terms, lying is considered bad, while honesty is considered good. But the truth is a little more complicated. Are all lies harmful? Even fibs? Are there instances we lie more often than others? And what happens in the brain when we do it? Thankfully, I’m not the only curious one because there is already some fascinating research out there looking for answers.

Are We Born Liars?

Yes, and we aren’t the only species to do it.

Child development research shows children progress through three primary stages to become adequate liars, beginning as toddlers. Around 2 to 3 years old is when children are first able to lie deliberately, but they’re too young to understand moral reasoning at this point.

A few theories are floating around to explain lying at such a young age, though, which include that toddlers want to present themselves in a more positive light, to avoid punishment, and in response to seeing the other person upset and wanting to make everything okay — rather than intentionally trying to deceive.

Transition to the second stage occurs between ages 3 and 4, when kids begin understanding first-order beliefs — registering their immediate wants and acting on them without considering the consequences of their actions or that other people have thoughts of their own. It’s also when kids develop the ability to regulate their body language to appear honest even when they aren’t.

However, kids at this stage still struggle with “semantic leakage control” before they turn five, meaning that they may tell a lie, but the following sentences they say after it will likely contradict the initial fib — which makes their lies easier to detect by adults.

Kids graduate to the third level of lying at around 7 and 8 years old which is when they gradually become better at controlling their semantic leakage by thinking ahead and providing other answers that don’t contradict their initial statement.

After that point, how well a child lies is just a matter of practice. Like any skill, the more they do it, the better they become. By the time they become pre-teens and teens, their brain development further allows them to create and maintain plausible lies. We become the best liars we can be in our twenties, but we become less proficient as we get older.

There are, of course, social components too. The responses a child receives after lying will influence their future lying habits — although, really, I think this could be said for anyone at any age.

And as I said at the beginning, other animals lie, or at least deceive, too. A study from a couple of years ago even found that dogs can sometimes even tell when their Human lies to them.