It’s official: The more we practice a lie, the better we get at convincing people it’s the truth.

That’s the conclusion of a new study in the journal Frontiers in Cognitive Science.  And while I know it sounds obvious, it helps explain why most children are terrible at lying – while con artists can make a career out of it.

In the study, researchers asked people to play an espionage game, where they had to memorize a false identity – including a fake name, date of birth, and hometown. Then, researchers quizzed each participant about both their fake and real identities – while measuring their response time and accuracy.

The result? The more time people had to practice their “cover story,” the less likely they were to slip up and tell the truth. And after just 20 minutes, researchers say most “liars” were indistinguishable from “truth-tellers!”

Psychologists say, lying takes work – and burns up a lot of brainpower. That’s because it requires memorizing two sets of information – the lie and the truth.  That’s why experts say you can usually spot a liar by listening for a pause.  Because people take longer to tell a lie than the truth.

It’s also why researchers hope this new study changes the way police investigate crimes. Because in the real world, experts say there’s usually a long delay between the crime and the interrogation, which potentially gives criminals more time to practice and perfect their alibi.