There are many kinds of smiles, such as a smile, a sneer, a silly smile, a bitter smile, a cold laugh, a big laugh, and a crazy laugh. But if we classify them into two types, it should be genuine smiles and fake smiles. The former comes from the heart, while the latter is forced for reasons like politeness, social norms, or strategies. So, is there a way to tell if someone is genuinely smiling or faking it?
Professor Michelle Spear of the University of Bristol in the UK wrote on The Conversation website that genuine or fake smiles depend on a combination of facial anatomy, neuroscience, and emotional authenticity.
Spear wrote that not all smiles are the same. From an anatomical perspective, there are at least two types of smiles—Duchenne smiles and non-Duchenne smiles. The former reflects genuine happiness, while the latter is often more social or strategic in nature.
The Duchenne smile is named after the 19th-century French neurologist Guillaume Duchenne de Boulogne. It involves two key sets of muscles. The first set of muscles is related to the corners of the mouth, such as the risorius muscle pulling the corners of the mouth outward, and the zygomaticus major muscle lifting them.
The second and most notable set of muscles is the orbicularis oculi, which tightens the muscles around the eyes, creating the familiar crow’s feet and a slight narrowing associated with warmth and joy.
Fake or polite smiles usually only involve the mouth muscles, with the eyes remaining wide open or unaffected. This type of smile appears stiff and meaningless—it’s an emotional facade.
Spear pointed out that both genuine and fake smiles rely on the seventh cranial nerve (also known as the facial nerve), which transmits signals from the brain to the muscles involved in facial expressions.
However, there is a crucial neurological distinction between the two—Duchenne smiles are often triggered by the brain’s limbic system, especially the amygdala. The amygdala is a group of almond-shaped neurons that process emotional significance.
In contrast, non-Duchenne smiles are typically controlled by the more conscious cortex, originating from the motor cortex. This difference means that genuine, emotion-driven smiles are involuntary and not consciously controlled.
Unless you genuinely feel the emotion behind the expression, you can’t easily contract your orbicularis oculi muscles. Even professional actors must use real memories or method techniques to convincingly achieve this.
Spear stated that humans are very good at perceiving emotional authenticity. Research shows that even 10-month-old infants can distinguish between genuine and fake smiles. From an evolutionary perspective, this ability may help us evaluate others’ credibility, identify true allies, and avoid deception.
In modern life, people’s sensitivity to subtle facial differences remains crucial. Politicians, customer service personnel, and public figures often rely on smiles to navigate complex interpersonal relationships. But observers—whether intentionally or unintentionally—often pick up on these subtle distinctions.
Fake smiles are not necessarily malicious. In fact, they serve important social functions such as easing awkward interactions, expressing politeness and respect, and resolving conflicts. They are an essential component of what sociologists call “emotional labor”—controlling emotions to meet others’ social or professional expectations.
However, if these smiles persist for a long time, they can lead to emotional exhaustion. Research on emotional labor suggests that being required to smile without genuine feelings—especially in a work setting—can result in increased stress, burnout, and even elevated cardiovascular pressure.
Although current artificial intelligence (AI) technology can replicate human smile expressions, many expressions still appear insincere if the muscles around the eyes do not slightly contract. Anatomy provides a standard for judgment.
Spear finally advised that next time you try to interpret someone’s expression, don’t just look at the mouth, pay attention to the eyes. The orbicularis oculi rarely lies.