A team in the United States asked volunteers to lie about whether they owned a particular playing card.
They found that among those tested, the same parts of the brain became active when someone was trying to conceal the truth.
The study could lead to brain scans being used instead of traditional lie detector tests.
These look for signs of stress such as a faster heart beat.
But don't worry - there's no sign of the new lie detector test being developed for use in schools or at home!