Depicted above is Pinocchio, in this case, from the 1940 Disney movie. Pinocchio, if you're somehow not familiar with him, is a sentient marionette made of wood, paint, and love. His one dream is to become a "real boy" and to get there, he believes he has to be a moral, upstanding citizen of the world who is worthy of such transformation. And to make it easier for him to do that -- in a roundabout sort of way -- Pinocchio comes with a little feature: if he lies, his nose grows, as seen above. And it's hard to lie when your nose grows when you do.

For those of us in the real world, that doesn't happen -- you can lie without anyone noticing a change in your nose. But that's probably because they don't have the right equipment. Because it turns out, when you lie, your nose likely knows it.

There is no perfect lie detection device. The polygraph, which is most often called a "lie detector," has been around for decades, but doesn't detect lies directly, if at all. Polygraphs measure changes in blood pressure, breathing rates, pulse, and other physiological factors. In theory, lying causes many of us to feel some degree of anxiety, and that anxiety should (again theoretically) be reflected in subconscious changes that can be picked up by such a device. That's certainly possible, but it's not something that you can rely upon when determining truth from lies is critical. So the science community has kept on looking for better ways to tell if someone is fibbing. About twenty years ago, researchers developed test using Functional magnetic resonance imaging (an "fMRI") to look at people's brains as they were lying. Scientific American explains:

An fMRI machine tracks blood flow to activated brain areas. The assumption in lie detection is that the brain must exert extra effort when telling a lie and that the regions that do more work get more blood. Such areas light up in scans; during the lie studies, the illuminated regions are primarily involved in decision-making.

By monitoring people's skin temperature with a special heat-sensing camera (think Predator vision) and asking them questions about subjective experiences, feelings, and emotions, the psychologists were able to discern the truthiness of people's responses. It turns out that when we lie, blood rushes to the center of our faces. If you're behind the lens of a thermography camera, the lies light up our noses and the inside corners of our eyes.