How they know when you lie

A trip  through the land of functional neuro-imaging and how they 'know' when you lie.

When you lie your brain has to work a little harder, because you are doing two different things: First, you're stopping yourself from telling the truth, and second, you're constructing a lie. 

The brain is more active when lying, and this can be  activity can with visualised with MRI. brain scanning.