How to spot a fake smile from the real thing

You've probably heard the claim that it takes more muscles to frown than to smile.

- Michelle Spear, The Independent

It's usually framed as a feel-good reason to turn your frown upside down — less effort, more joy. But anatomically, the numbers don't quite add up. We've all seen it — the smile that doesn't quite reach the eyes. From awkward family photos to strained workplace pleasantries, our brains often detect that something is off long before we consciously realise why.

But what is it about a smile that makes it feel sincere — or fake? The answer lies in a surprising blend of facial anatomy, neurology and emotional authenticity. Not all smiles are created equal, and anatomically speaking, there are at least two distinct kinds: the Duchenne smile, which reflects genuine happiness, and the non-Duchenne smile, which tends to be more social or strategic.

Named after 19th-century French neurologist Guillaume Duchenne de Boulogne, the Duchenne smile activates two key muscle groups. The first group is associated with the corners of the mouth — where, for example, the risorius (from the Latin to smile) draws the corners outward and the zygomaticus major muscle lifts them.