If you don't trust that smile on the faces of your friends, you might want to keep a close left eye on them.
Research suggests that the brain's right hemisphere can read emotions on the upper half of people's faces better than the left hemisphere can. Past research suggests that one's upper face displays inborn emotions, while the lower face exhibits learned emotions. "You can always put a smile on your face," says lead researcher Calin Prodan, Ph.D., a University of Oklahoma neurology resident—but the eyebrows, forehead and eye creases often reveal true feelings.
In a study, Prodan presented drawings of faces displaying conflicting emotions on their upper and lower halves so that the images registered in only the left or right visual fields of the study's participants. Initially, the subjects only recognized emotions on the lower face. "We tend to focus on the lower half of the face since eye-to-eye contact is pretty aggressive," he says.
But when subjects focused on the upper half of the face, there were almost twice as many accurate readings of emotions for the right brain—or the left visual field—as for the left brain. So if you think you're being handed a line, make sure to keep good eye contact.