How the Brain Senses a Smile

(Credit: Djomas/Shutterstock) When you see a great big smile, you know that someone is happy. Pretty simple, right? Such an inference is less a product of deductive reasoning and more like an instinctual reaction — we just know what certain facial expressions mean, we don't have to think about it. And researchers from Ohio State University say they've pinpointed the region of the brain that goes to work whenever we are confronted with raised eyebrows, wrinkled noses, taut lips and other facial contortions. Located in the back, right-hand side of the brain, the small area is called the posterior superior temporal sulsus (pSTS), and researchers say it helps us process facial expressions.