We express fear when we feel physically or psychologically threatened.

The facial expression of fear is often confused with surprise. But when we’re surprised, our eyes open wider than when we’re afraid, and our mouth isn’t pulled sideways, like it is here; instead, our jaw drops and the mouth hangs open. Plus, our eyebrows are relatively flat when we’re afraid; they arch more when we’re surprised.

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This is a classic display of a genuine smile, called a Duchenne smile, which signals happiness.

It’s defined by two muscle movements. The movement common to all smiles is the zygomatic major muscle pulling the lip corners up. But, critically, what reveals this as a genuine smile is what happens around the eyes: The muscles tighten, making those wrinkles, or crow’s feet, around the sides of the eyes and creating that pouching of the lower eyelid. When you see these signs, the person isn’t just smiling politely; he’s feeling genuine happiness.

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You see these muscle movements—in the lips, around the eyes, and in the brow—when people are feeling aggressive, threatened, or frustrated. Researchers think we make this expression when we’re angry because it could protect the face in a physical conflict—for example, the furrowed eyebrows could protect the eyes.

People often confuse anger and disgust, but disgust involves a raised upper lip and a wrinkle in the nose that you don’t see here.

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When people are embarrassed, they avert their gaze, which means they move their head down and to the side, exposing their neck. And the embarrassed smile is different from other smiles: The lips press together tightly, reflecting feelings of restraint or inhibition.

Embarrassment can look like shame, but when we’re ashamed, our head moves straight down, not to the side, and we don’t smile.

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Pride involves signs of dominance. The corners of the lips rise slightly, signaling that the person is happy. But what distinguishes this from happiness is that the head tilts back, with a slight jaw-thrust. Those are classic signs of power and dominance—they suggest that we’re feeling strong.

The expression of pride is also close to the expression of contempt. They both involve a backward head tilt, but contempt doesn’t involve a slight smile like pride does; instead, with contempt the lip movement is asymmetrical—only one side tightens.

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Surprise is often confused with fear. But when we’re afraid, our lower eyelids tighten and our eyebrows look flat and tense; with surprise, our upper eyelids rise up and our eyebrows arch. Also, our jaws drop when we’re surprised, but our lip corners go sideways when we’re afraid, making the mouth look tighter.

Some experts believe our eyes open wide like this because when we’re confronted with something surprising—a long-lost friend, an unexpected award—we try to absorb as much of this new information as possible.

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Contempt is when you look down on somebody derisively or suspiciously. What’s important about the expression of contempt is that the lips tighten on one side of the face but not the other. If the tightening were on both sides of the face, the person could be swallowing or salivating.

People often confuse contempt with disgust. But disgust involves the raising of the upper lip, and the bridge of the nose wrinkles. We express disgust about noxious things, not those about which we’re derisive or suspicious.

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When we feel disgust, the muscles above the upper lip pull up, raising the upper lip, wrinkling the nose, and narrowing the eyes.

People often confuse disgust and anger. But anger tightens the mouth and lowers the eyebrows more significantly, and raises the upper eyelid. With disgust, the mouth opens and the tongue comes out, just in case you need to throw up.

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This is a coy, flirtatious smile. What conveys flirtatiousness is when someone turns his or her head away to signal ‘I’m not interested in you,’ but simultaneously makes eye contact. That’s a universal display that reflects the ambivalence of flirtation—the flirter avoids and approaches someone at the same time.

Someone flirting gives off signals of pleasure, as indicated by the zygomatic major muscle pulling the lip corners up, which also raises the cheeks slightly. Plus, the eyes are narrower than in a neutral state because the orbicularis oculi muscles around the eyes contract, suggesting feelings of happiness.

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When we feel pain, our facial muscles move in ways that contract the face and protect us from harm. In the upper half of the face, the orbicularis oculi muscles around the eyes contract, closing the eyes tightly, and the corrugator muscle lowers our eyebrows. In the lower half of the face, our lips tighten and press upwards.

You’ll see this particular expression especially when people are experiencing psychological pain, such as when they see other people suffer. It’s an expression closely related to sadness. But rather than suffering in their own sadness, they experience the pain and suffering of others through empathy.

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When people feel sympathy or compassion, the corrugator muscles pull the eyebrows in and up, their lips press together, and their head tilts forward slightly—a sign of social engagement.

The expression of compassion is most often confused with sadness. The eyebrow movements are similar in sadness and compassion, but with compassion the lips press together; when we feel sad, our lips pull down.

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The tell-tale signs of genuine amusement are the open mouth and the backwards head movement. And like a genuine smile, you can tell a genuine laugh when you see the muscles contracting around the eyes, making crow’s feet.

Genuine laughter often relaxes all muscle movements in the body because of shifts in our respiration patterns that happen when we laugh. This rapid shift to a state of relaxation shuts off feelings of aggression or frustration—we’re cooperating with other people, not competing.

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When we’re interested in something, the frontalis muscles raise our eyebrows straight up, and our lip corners turn up in a slight smile, suggesting we’re feeling pleasure.

The expression of interest is related to the expression of happiness. But when we’re happy, we’ll show more exaggerated upward movements of our lip corners, and the muscles around the eyes will contract more, without the eyebrow raising straight up.

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Sadness is characterized by oblique eyebrows, where the corrugator muscles pull the eyebrows in, but the inner part of the frontalis muscle pulls them up. There’s also a little pouching in the inner part of the forehead, and people will often look down. Plus, the corners of the lips are pulled straight down, giving the mouth a curved look.

The expression of sadness is often confused with shame, and it shares the oblique eyebrow muscle movements of compassion.

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Desire is signaled through the mouth, with lip bites, puckers, or (as in this case) lip licks. The mouth is probably so strongly linked to desire because of the connection to kissing. People often make this facial expression when they’re interested in someone else sexually, but not necessarily romantically.

Desire is obviously a relative of love, but when people feel loving and trusting and devoted to someone else, as opposed to sexually aroused, they won’t necessarily make this kind of gesture with their mouth. Instead, they’ll often smile in a way that suggests happiness, with a head tilt to the side.

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Shame is a very simple display but a powerful one. It simply involves gaze aversion, with the head moving down so that the chin tucks into the neck. It’s the opposite of pride: Whereas with pride our head tilts back and our chin goes up, shame often constricts our posture as a sign of submissiveness.

This expression is frequently confused with sadness. But shame doesn’t involve the muscle movements of the sad face—the eyebrows pulled in and partly up, with the lip corners moving down.

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This is a non-Duchenne smile—a smile that doesn’t signal true happiness. It suggests that the person is trying to seem polite and cooperative, but they don’t genuinely feel happy.

The zygomatic major muscle is pulling the lip corners up, but there are no signs of real joy around the eyes—no crow’s feet around the sides, no pouching of the lower eyelid, no raising of the cheek.

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With about 30 percent of embarrassment episodes, people touch their face, which is happening here. Some experts believe the face touch is a defensive movement, to protect the face after the person violated some social rule.

In some parts of the world, people make a similar hand gesture when they’re ashamed. But with shame, the head moves straight down, not to the side, and there’s no slight smile.

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When we feel pain, our facial muscles contract the face and protect us from harm.

In the upper half of the face, the orbicularis oculi muscles around the eyes contract, closing the eyes tightly, and the corrugator muscle lowers our eyebrows. In the lower half of the face, our lips tighten and press upwards. Especially when experiencing physical pain, people will sometimes contract their neck, as is happening here, making this look even more like a display of self-defense.

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When we feel love, our facial expression often resembles happiness: The zygomatic major muscle pulls the lip corners up, and there’s a tightening of the lower eyelid.

But the distinct expression of love combines these muscle movements with a tilt of the head to the side. That’s a sign of intimacy and connection beyond just happiness.

Finished!