Jun 02, 2025 12:30:00

What is the scientific method to spot a 'fake smile'?

In human society, there are many occasions when we have to smile as a matter of courtesy, even if we are not genuinely enjoying or amused.

Michelle Speer , a professor of anatomy at the University of Bristol in the UK, explained the scientific method of identifying such 'fake smiles.'

The anatomy of a smile: how to spot a fake from the real thing
https://theconversation.com/the-anatomy-of-a-smile-how-to-spot-a-fake-from-the-real-thing-256481

'We've all seen a smile that doesn't reach the eyes. From an awkward family photo to a forced office greeting, our brains know something's wrong long before we consciously realize why,' says Speer, pointing out that humans have the instinct to spot a fake smile.

Anatomically, there are at least two types of smiles. One is the ' Duchenne smile,' which is said to be a genuine smile, and the other is the 'non-Duchenne smile,' which tends to be more social. People intuitively detect the difference between these and judge whether a smile is fake or not .

Named after the 19th-century French neurologist

Duchenne de Boulogne , the Duchenne smile activates two main muscle groups : the risorius (Latin for 'smile') , located on the side of the mouth, pulls the corners of the mouth outward, and the zygomatic major muscle , which runs from the top of the cheek to the corners of the mouth, lifts them.

The second muscle group that's important for creating a genuine smile is the orbicularis oculi , located around the eyes. This tightens the muscles around the eyes, creating the crow's feet and narrowing of the eyes that we associate with warmth and joy when we smile.

On the other hand, most fake smiles are produced only by the muscles around the mouth, and the orbicularis oculi is not used properly. As a result, the eyes remain wide open or static, making the smile look emotionless and robotic, Speer explains.

Although both real and fake smiles are produced by

the cranial nerve VII (facial nerve) , there is a neurological difference between them: real smiles are generated by the limbic system, the emotional core of the brain , specifically the amygdala , which processes the manifestation of emotions.

On the other hand, fake smiles are often generated in the motor cortex , which is under more conscious cortical control, making genuine smiles, which are driven by emotions, more involuntary.

Speer points out that it's hard to convincingly contract the orbicularis oculi unless you truly feel the emotion, which is why professional actors use method acting techniques to convincingly smile, such as recalling happy memories from the past or reliving the emotions of the character.

Humans have a good ability to distinguish between real and fake smiles, with a 2007

study showing that even 10-month-old babies can tell the difference between real and fake smiles. Speer believes that our ability to tell the difference between real and fake smiles has helped us assess the trustworthiness of others and distinguish between genuine peers.

In modern society, politicians, customer service representatives, and celebrities frequently use social smiles to navigate complex interpersonal expectations, but fake smiles aren't necessarily bad; they can smooth over awkward interactions, convey politeness, defuse conflict, and provide context.

On the other hand, it has been pointed out that emotional labor , which requires controlling facial expressions to meet social and professional expectations, is mentally taxing. Studies of emotional workers and workers who use emotions as part of their service have suggested that smiling without genuine emotion can lead to increased stress, burnout , and cardiovascular strain.

Many chatbots and virtual assistants these days have synthetic facial expressions programmed to mimic human expressions, but without the microscopic muscle contractions around the eyes, smiles would look unnatural.

'The next time you're trying to decipher someone's facial expression, don't just look at their mouth -- look at their eyes. The orbicularis oculi rarely lies,' advises Speer.