Smiles and Frowns Are Contagious for a Reason


You know what they say: when you’re smiling, the whole world smiles with you. As it turns out, there’s a reason for that. A study published today in the journal Trends in Cognitive Sciences shows that mirroring other people’s facial expressions helps us connect. 

Scientists have known for some time now that our facial expressions can actually change our moods. A 2012 study found that people who held chopsticks in their mouths lengthwise, forcing their faces into fake smiles, felt happier and less stressed than people who maintained neutral expressions. 

We have a lot to gain from connecting with and understanding other humans; at times, that can mean the difference between life and death. As a result, we have evolved mechanisms that make those connections easier.

“Most people are face perception experts,” the authors write. “Faces, especially those expressing emotion, automatically capture our attention, and we extract the emotional meaning of those faces in a matter of a few hundred milliseconds, even subconsciously. Expressions of intense emotion, such as a wide-eyed expression of fear or a toothy grin, may have evolved to be highly distinguishable signals, easily recognizable even from a distance.” 

This study found that humans subconsciously “try on” each other’s expressions in order to understand how others are feeling. The authors reviewed 15 recent journal articles on facial expression mimicking and the role of muscle movements in emotion. There, they found evidence for what they call the sensorimotor simulation model of emotion perception. In plain English, they’re suggesting that we move our facial muscles to mimic the face in front of us, and that this movement triggers the memory of associated emotions, which triggers real emotion in the moment. 

An example: You’re used to frowning when we feel sad or angry. If you’re sitting in a coffee shop with your friend and she is frowning, even a little bit, you might frown too, without even realizing it. As your brain recognizes the frown on your face, it calls up examples of frowning in your own life, and the feelings that went along with them. You begin to feel just a little bummed. Because this is how your friend is feeling, it helps you connect and relate to her. Voila: social success.

The authors note that this skill is dependent on having a clear view of someone else’s face and being able to replicate their expression. Many people with autism avoid making eye contact, which may contribute to their difficulty recognizing others’ emotions. People who have had strokes or experienced Bell’s palsy may have trouble moving their facial muscles, which limits how much they can mimic the faces in front of them. People who were born with facial paralysis, on the other hand, have often developed other ways to tap into that same empathy.

For their next project, the researchers intend to study how humans perceive and identify other people’s facial expressions.

The American Museum of Natural History
10 Surprising Ways Senses Shape Perception
The American Museum of Natural History
The American Museum of Natural History

Every bit of information we know about the world we gathered with one of our five senses. But even with perfect pitch or 20/20 vision, our perceptions don’t always reflect an accurate picture of our surroundings. Our brain is constantly filling in gaps and taking shortcuts, which can result in some pretty wild illusions.

That’s the subject of “Our Senses: An Immersive Experience,” a new exhibition at the American Museum of Natural History in New York City. Mental Floss recently took a tour of the sensory funhouse to learn more about how the brain and the senses interact.


Woman and child looking at pictures on a wall

Under normal lighting, the walls of the first room of “Our Senses” look like abstract art. But when the lights change color, hidden illustrations are revealed. The three lights—blue, red, and green—used in the room activate the three cone cells in our eyes, and each color highlights a different set of animal illustrations, giving the viewers the impression of switching between three separate rooms while standing still.


We can “hear” many different sounds at once, but we can only listen to a couple at a time. The AMNH exhibit demonstrates this with an audio collage of competing recordings. Our ears automatically pick out noises we’re conditioned to react to, like an ambulance siren or a baby’s cry. Other sounds, like individual voices and musical instruments, require more effort to detect.


When looking at a painting, most people’s eyes are drawn to the same spots. The first things we look for in an image are human faces. So after staring at an artwork for five seconds, you may be able to say how many people are in it and what they look like, but would likely come up short when asked to list the inanimate object in the scene.


Our senses often are more suggestible than we would like. Check out the video above. After seeing the first sequence of animal drawings, do you see a rat or a man’s face in the last image? The answer is likely a rat. Now watch the next round—after being shown pictures of faces, you might see a man’s face instead even though the final image hasn’t changed.


Every cooking show you’ve watched is right—presentation really is important. One look at something can dictate your expectations for how it should taste. Researchers have found that we perceive red food and drinks to taste sweeter and green food and drinks to taste less sweet regardless of chemical composition. Even the color of the cup we drink from can influence our perception of taste.


Sight isn’t the only sense that plays a part in how we taste. According to one study, listening to crunching noises while snacking on chips makes them taste fresher. Remember that trick before tossing out a bag of stale junk food.


Have you ever been so focused on something that the world around you seemed to disappear? If you can’t recall the feeling, watch the video above. The instructions say to keep track of every time a ball is passed. If you’re totally absorbed, you may not notice anything peculiar, but watch it a second time without paying attention to anything in particular and you’ll see a person in a gorilla suit walk into the middle of the screen. The phenomenon that allows us to tune out big details like this is called selective attention. If you devote all your mental energy to one task, your brain puts up blinders that block out irrelevant information without you realizing it.


Girl standing in optical illusion room.

The most mind-bending room in the "Our Senses" exhibit is practically empty. The illusion comes from the black grid pattern painted onto the white wall in such a way that straight planes appear to curve. The shapes tell our eyes we’re walking on uneven ground while our inner ear tells us the floor is stable. It’s like getting seasick in reverse: This conflicting sensory information can make us feel dizzy and even nauseous.


If our brains didn’t know how to adjust for lighting, we’d see every shadow as part of the object it falls on. But we can recognize that the half of a street that’s covered in shade isn’t actually darker in color than the half that sits in the sun. It’s a pretty useful adaptation—except when it’s hijacked for optical illusions. Look at the image above: The squares marked A and B are actually the same shade of gray. Because the pillar appears to cast a shadow over square B, our brain assumes it’s really lighter in color than what we’re shown.


The human brain is really good at recognizing human faces—so good it can make us see things that aren’t there. This is apparent in the Einstein hollow head illusion. When looking at the mold of Albert Einstein’s face straight on, the features appear to pop out rather than sink in. Our brain knows we’re looking at something similar to a human face, and it knows what human faces are shaped like, so it automatically corrects the image that it’s given.

All images courtesy of the American Museum of Natural History unless otherwise noted.

Learn to Spot the Sneaky Psychological Tricks Restaurants Use

While dining out, you may have noticed (but perhaps didn’t question) some unusual features—like prices missing dollar signs, or burgers served on plates that could accommodate a baby cow.

These aren’t just arbitrary culinary decisions, as the SciShow’s Hank Green explains in the video below. Restaurants use all kinds of psychological tricks to make you spend more money, ranging from eliminating currency symbols (this makes you think less about how much things cost) to plating meals on oversize dinnerware (it makes you eat more). As for the mouthwatering language used to describe food—that burger listed as a "delectable chargrilled extravagance," for example—studies show that these types of write-ups can increase sales by up to 27 percent.

Learn more psychological tricks used by restaurants (and how to avoid falling for them) by watching the video below. (Or, read our additional coverage on the subject.)


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