How do emotions work? This might seem like an odd question since we all experience emotions every day: happiness at seeing an old friend, sadness while watching a tragic film, fear of losing the ones we love.

Emotions seem automatic. Your heart skips a beat, your nerves do a little dance, your face moves in familiar ways, and you are carried away by the experience. Nevertheless, from a scientific standpoint, what are emotions really?

For centuries, famous thinkers like Plato, Aristotle, Darwin and Freud, as well as countless other scientists, have tried to explain emotion using common sense. Emotions feel natural and uncontrollable, the reasoning went, so they surely must be built into us from birth.

In recent years, however, the field of neuroscience – the study of how the human brain creates the human mind – has surged. With this interest has come intense research and renewed debate on the nature of emotions.

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A few decades ago, scientists could only guess how the brain creates our emotional experiences. Now, though, we can use brain-imaging to harmlessly peer inside a head. This allows us to observe neural activity, moment by moment, inside living people.

And when it comes to emotion, what we see in those brains seems to defy common sense. Emotions are not what most people think they are.

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Here’s what I mean. Suppose you’re walking in the woods and you see a bear, and you instantly feel afraid. What happened inside you? The traditional explanation goes like this. As soon as you saw the bear, some dedicated part of you – like a ‘fear circuit’ in your brain – sprang into action, triggering your body to react in a predetermined way. Your heart raced, your blood pressure soared, and your face formed an expression of fear that’s said to be universal across all human cultures.

In this classical view of emotion, the firing fear circuit, the bodily changes, and the facial expression supposedly form a distinct, detectable ‘fingerprint’ that distinguishes fear from all other emotions. That fingerprint was presumably passed down to humans through evolution, along with fingerprints for other emotions.

Changing times

As compelling and intuitive as the classical view may be, it can’t possibly be correct. Scientists have been searching for emotion fingerprints in the face, body and brain for over 100 years without success.

Occasionally, you’ll see a news story that scientists have found fingerprints of happiness, sadness, anger, fear, or other emotions in humans or other animals, but when other scientists retest those claims, they invariably don’t hold up. For example, for many years, scientists believed that the brain’s ‘fear circuit’ was a region called the amygdala.

If you google ‘amygdala fear’ you can still find thousands of articles that make this claim. Nevertheless, it’s not true. We now know definitively that some people who lack an amygdala can still feel fear. Not only that, but the amygdala is involved in dozens of other mental functions (such as thinking, memory, empathy and all other emotions), so it’s clearly not a fear circuit. The same is true of every other brain area that has ever been claimed as the home of an emotion.

The main problem with the classical view of emotion is that emotional life has too much variety to be shoehorned into a bunch of universal fingerprints. Do your eyes widen every time you’re afraid? Do you always gasp? Of course not. People who feel fear might scream, cry, laugh, close their eyes, clench their fists, wave their arms, strike out, faint, or even stand motionless.

We also smile only about 12 per cent of the time when we’re happy, according to a recent statistical analysis of many studies, and scowl 28 per cent of the time when angry. Another study on babies showed that their facial movements are pretty much indistinguishable in fear and anger. No emotion has a single fingerprint in the body. Instead, variety is the norm.

The Himba people do not associate laughter with an emotion – they simply perceive the person as laughing © Getty Images
The Himba people do not associate laughter with an emotion – they simply perceive the person as laughing © Getty Images

Not only that, but different cultures have different emotions. For example, the German language contains three distinct angers with different meanings, while Russian has two and Mandarin has five.

Plenty of cultures have emotions that don’t translate into English. The Ifaluk people of Micronesia, for example, have an emotion, ‘fago’, that can mean love, empathy, pity, sadness, or compassion, depending on context. Even more intriguing, some cultures don’t have a unified concept of ‘emotion’ for the events that Westerners experience as emotional.

One example comes from the Himba people of Namibia. When you see somebody laughing, you might perceive that they’re happy or amused, but the Himba would simply perceive the person is laughing. They don’t perceive laughter in mental terms. Throughout the world, the sheer variety of emotional life is vast – too vast to be explained by the classical view.

So, how are emotions made?

The answer of how emotions are made flies in the face of common sense, because the human brain is a master of deception. Like a magician, it creates incredible experiences as diverse as joy, envy, curiosity and wrath without revealing how it does so. But thanks to recent advances in brain imaging, which allows scientists to observe a living brain as it thinks, feels, and perceives its surroundings, we now have a pretty good idea of the brain’s secret technique for making emotion.

Your brain’s most important job is keeping your body alive. To accomplish this, it devotes most of its time to predicting what will happen next, so your body can be ready for any contingency.

Studies show that your brain spends 60 to 80 per cent of its energy on prediction. In every moment, your brain issues thousands of predictions at a time, based on past experience, and the ones that win are (usually) the ones that fit the situation in the next moment. When you walk, for example, each time you lift your foot to take the next step, your brain anticipates how your foot will land. If your brain gets this wrong, you might trip. If you’ve ever been in an airport on a moving walkway, and have stumbled as you stepped off (or the last step just feels weird), you know how prediction error feels.

Your brain also makes predictions about other people in the world. Studies show that when you meet strangers, you like and trust them more when their facial movements (like smiles or scowls) match your brain’s guesses. Remarkably, you even consciously see their face more quickly!

Listen to our interview with Dr Lisa Feldman-Barrett in the Science Focus Podcast

Along with predictions about the world, your brain also makes them about your body so you stay alive and healthy. It forecasts when your heart should speed up or slow down, when your blood pressure should rise and fall, when your breathing should deepen, and when you need more salt, sugar, water or hormones, and attempts to meet those needs before they arise. It’s like running a budget for your body, but instead of money, the currency is biological.

This budgeting process continues through your entire life, and most of the time, you aren’t aware of it. But it produces something you know well: your mood.

Somehow, through a mysterious process that nobody understands, physical movements inside your body become mental. You feel generally pleasant, unpleasant, or anywhere in between. You feel calm or agitated. Your mood is like a barometer for the health of your body. It’s with you every moment of your life, though much of the time it’s in the background and you don’t notice it.

This same process produces your emotions completely outside your awareness. Let’s go back to our ‘bear in the woods’ example. When you’re walking in the woods, your brain issues thousands of predictions in every moment, based on past experience. It anticipates each step, the crunch of the dry leaves underfoot, and the look of the greenery above you. It forecasts the heart rate and breathing that you’ll need to keep up the pace.

Your brain even issues predictions about animals appropriate to the setting, such as bears, and prepares your body to deal with them. It sends signals to your heart to beat faster, your lungs to breathe deeper, and so on, and prepares your body to run. At the same time, your brain guesses how you will feel in a moment from now when you start running and produces an agitated mood.

This entire collection of predictions comes from your past experiences of fear. So, if an actual bear shows up in the next moment, you’re already starting to run and experiencing fear. That’s why fear feels so automatic in that situation, like a reflex. Your brain explains your body’s sensations and launches your movements before you’re consciously aware.

More than a feeling

But what if there’s no bear? That’s a prediction error, and you’ll be left with an agitated feeling with no apparent cause. If you’ve ever walked in the woods at night and have suddenly startled for no apparent reason, you’ve experienced this.

There’s even a curious third possibility that there’s no bear present, but you see a bear anyway, for a moment. You’ve probably experienced this too. Have you ever seen a person that you thought you knew, but then realised it’s a stranger? Same thing. Your brain predicted someone you know, based on past experience, and just for a second, you saw them.

In short, emotions are your brain’s best guesses for what your body’s sensations mean, based on your situation. When your face feels hot as a driver cuts you off in traffic, you might experience the heat as anger. If you feel the same hot face when you’re inches away from having your first kiss, you might experience it as excitement. Or if you feel the same sensation as you walk out of the sea and realise your swimming costume has fallen down, you might experience it as embarrassment.

Your brain makes meaning from the identical sensation in different ways, depending on context. That’s how emotions are made. They are not built-in at birth. They are built in the moment.

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In a sense, your emotions are constructed unconsciously from three ingredients: your body budget, your current situation, and predictions from past experience. If you modify any of these ingredients, you can take some control over your emotions. I’m not saying this is easy, but it’s possible.

Changing your body budget is the most straightforward of the three (but again, not easy). Eat healthily, get enough sleep, and exercise regularly, and your brain won’t have to work as hard to keep your body budget in balance. That means your mood will be less negative and your brain will have fewer opportunities to create unpleasant emotions.

You can change the second ingredient, your current situation, in a variety of ways. You can directly adjust your surroundings by moving to another location, like leaving the room or taking a walk. If that’s not possible, you can indirectly change your surroundings by paying attention to other things around you – that is, being mindful.

The third ingredient, your predictions from past experience, is the toughest to alter because it’s impossible to change your past. Yet if you take action in the present, you can modify your brain’s predictions in the future, changing your future emotions. For example, in my family, we came up with an idea we call the ‘emotional flu’.

Have you ever felt wretched, like you’re a horrible person, everybody hates you, and the world is going to end… but in fact, there’s nothing actually wrong with your life? That’s the emotional flu – you’re having an unpleasant physical feeling, probably from a disrupted body budget, and your brain has constructed all sorts of negative explanations that are deeply personal.

Your brain has to constantly balance your body’s budget to keep you healthy. If things get out of whack, it can impact your mood and create bad emotions. Eat healthily, get enough sleep and exercise regularly to give your brain a helping hand © Getty Images
Your brain has to constantly balance your body’s budget to keep you healthy. If things get out of whack, it can impact your mood and create bad emotions. Eat healthily, get enough sleep and exercise regularly to give your brain a helping hand © Getty Images

To deal with these feelings, we took inspiration from the real flu. The influenza virus isn’t personal – it simply takes up residence in your lungs. Likewise, we worked hard to view the wretchedness as purely physical, and to treat the symptoms with naps, walks, exercise, hugs, or whatever works.

By repeatedly reframing the situation from personal to physical, my family and I changed our brains’ future forecasts, making it easier to create the non-personal, non-judgmental, emotional flu. This was challenging to do at first, but it got easier with practice, and we’ve passed the idea along to friends who have also succeeded.

I’m not saying you can tweak a few predictions and cure a serious disorder like anxiety or depression, but it’s possible to make tangible improvements in your life. That said, this way of thinking about emotion does have implications for understanding mental illness.

For hundreds of years, people have drawn a boundary between mental and physical illness. Cancer, heart disease and diabetes are seen as disorders of the body, while depression and anxiety are often viewed as ailments of the mind. But we now know that your brain constantly regulates your body budget, and when the budget’s in the red, you feel bad.

This suggests that problems with metabolism, traditionally associated with the body, are at the core of mood-related mental illnesses such as depression and anxiety. It also helps explain why physical illnesses like diabetes and heart disease have persistent mood symptoms. The boundary between the physical and the mental is more porous than previously thought, and understanding this is key to finding new pathways for prevention and treatment.

New outlook

This new view of emotion suggests something important about artificial intelligence. Is it possible to build a machine that can read people’s emotions? Companies such as Facebook, Google, and Microsoft are betting that the answer is yes. They’re spending millions of research dollars to detect emotion via software, by examining faces and bodies as their owners experience emotion.

But emotions aren’t readable in the face and body alone, because emotions have no fingerprints, and variety is the norm. This means these approaches are asking fundamentally the wrong questions. Tech companies must include more data about a person’s context, and embrace the variation in real emotion life.

A tougher question is, can we build a computer that can feel emotion? Our new view of emotion offers an intriguing possibility. If emotion is constructed in part by regulating a body budget, then for a machine to experience emotion, it must have something like a body. Not necessarily a human-like body, but a set of complicated, interacting systems with energy needs that must be kept in balance. (No doubt some clever AI programmers can figure out a solution.) This will bring us closer to creating a machine that can feel and be empathetic.

  • This article was first published in May 2018.


Lisa is a professor of psychology at Northeastern University and the author of Seven And A Half Lessons About The Brain (£14.99, Picador). She is one of the most cited scientists in the world for her research into psychology and neuroscience. Lisa is Chief Science Officer for the Center for Law, Brain & Behavior at Massachusetts General Hospital, and received a National Institutes of Health Director’s Pioneer Award for her revolutionary research on emotion in the brain.