Your brain is inherited from people who survived. This may seem obvious, but when you look closer at the huge survival challenges of the past, it seems like a miracle that all of your direct ancestors kept their genes alive. You have inherited a brain that is focused on survival. You may not think you are focused on survival, but when you worry about being late for a meeting or eating the wrong food, your survival brain is at work. When you worry about being invited to a party or having a bad hair day, your survival brain sees the risk of social exclusion, which was a very real threat to your ancestors. Once you’re safe from immediate threats like hunger, cold, and predators, your brain scans for other potential threats. It’s not easy being a survivor!
Consciously, you know that bad hair is not a survival threat, but brains tuned to social opportunities made more copies of themselves. Natural selection built a brain that rewards you with a good feeling when you see an opportunity for your genes and alarms you with a bad feeling when you lose an opportunity. No conscious intent to spread your genes is necessary for a small social setback to trigger your natural alarm system.
These responses are rooted in your brain’s desire to survive, but they’re not hard-wired. We are not born to seek specific foods or avoid specific predators the way animals often are. We are born to wire ourselves from life experience. We start building that wiring from the moment of birth. Anything that made you feel good built pathways to your happy chemicals that tell you “this is good for me.” Whatever felt bad built pathways that say “this is bad for me.” By the time you were seven years old, your core circuits were built. Seven may seem young, since a seven-year-old has little insight into its long-term survival needs. But seven years is a long time for a creature in nature to be practically defenseless. This is why we end up with core neurochemical circuits that don’t always match up with our survival needs.
In short, your brain has some quirks:
This is why our neurochemical ups and downs can be so hard to make sense of.
The feeling we call “happiness” comes from four special brain chemicals: dopamine, endorphin, oxytocin, and serotonin. These “happy chemicals” turn on when your brain sees something good for your survival. Then they turn off, so they’re ready to activate again when something good crosses your path.
Each happy chemical triggers a different good feeling:
“I don’t define happiness in those terms,” you may say. That’s because neurochemicals work without words. But you can easily see how strong these motivations are in others. And research illuminates these impulses in animals. As for yourself, your verbal inner voice may seem like your whole thought process until you know the chemistry of your inner mammal.
Dopamine: the joy of finding what you seek
Endorphin: the oblivion that masks pain
Oxytocin: the comfort of social alliances
Serotonin: the security of social importance
Happy chemicals are controlled by tiny brain structures that all mammals have in common: the hippocampus, amygdala, pituitary, hypothalamus, and other parts collectively known as the limbic system. The human limbic system is surrounded by a huge cortex. Your limbic system and cortex are always working together to keep you alive and keep your DNA alive. Each has its special job:
Your inner mammal rewards you with good feelings when you do something good for your survival. Each of the happy chemicals motivates a different type of survival behavior:
You might come up with different motivations in your verbal brain, but your inner mammal decides what feels good.
Dopamine: seek rewards
Endorphin: ignore physical pain
Oxytocin: build social alliances
Serotonin: get respect from others
The mammal brain motivates a body to go toward things that trigger happy chemicals and avoid things that trigger unhappy chemicals. You can restrain yourself from acting on a neurochemical impulse, but then your brain generates another impulse, seeking the next-best way to meet your survival needs. You’re not a slave to your animal impulses, but nor do you just operate on pure data, even if you believe you are doing that. You are always looking for a way to feel good, deciding whether to act on it, and then looking for the next best way of feeling good.
Animals accept their neurochemical impulses without expecting a verbal rationale. That’s why animals can help us make sense of our own brain chemicals. The goal here is not to glorify animals or primitive impulses; it is to know what turns on our happy chemicals.
For example, a hungry lion is happy when she sees prey she can reach. This is not philosophical happiness, but a physical state of arousal that releases energy for the hunt. Lions often fail in their hunts, so they choose their targets carefully to avoid running out of energy and starving to death. When a lion sees a gazelle she knows she can get, she’s thrilled. Her dopamine surges, which revs up her motor to pounce.
A thirsty elephant is happy when he finds water. The good feeling of quenching his thirst triggers dopamine, which makes permanent connections in his neurons. That helps him find water again in the future. He need not “try” to learn where water is. Dopamine simply paves a neural pathway. The next time he sees any sign of a water hole, electricity zips down the path to his happy chemicals. The good feeling tells him “here is what you need.” When he’s exhausted and dehydrated, a sign of a reward at hand triggers the good feeling that spurs him on. Without effort or intent, happy chemicals promote survival.
But happy chemicals don’t flow constantly. The lion only gets more happy chemicals when she finds more prey, and the elephant only releases them when he sees a way to meet a need. There is no free happy chemical in the state of nature. Good feelings evolved because they get us to do things that promote survival.
Animals make survival decisions with very little cortex. Their limbic system is enough to decide what’s good for them. It motivates them to approach when a good feeling is released and to avoid when a bad feeling is released. This simple system kept our animal ancestors alive for millions of years and is still working inside us.
The following figure shows how the basic chassis of our brain stayed the same while the size of the parts changed immensely. Nature tends to build on what’s there instead of starting over with a blank sheet. Mammals built onto the reptile brain and humans built onto the mammal brain. We humans have a large stock of extra neurons ready to wire in new experience. Reptiles have a miniscule stock of neurons so they rarely adapt to new experience. But the reptile brain is skilled at scanning the world for threats and opportunities. If you ever feel like you are of two minds, or that your mind is going in different directions, this chart makes it easy to see why.
| cortex
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extra neurons that store life experience by growing and interconnecting |
| limbic system
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structures that manage neurochemicals, such as the amygdala, hippocampus, hypothalamus |
| reptilian brain
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the cerebellum and brain stem (medulla oblongata and pons), which manage routine bodily functions |
| human |
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| chimpanzee |
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| gazelle |
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| mouse |
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| lizard |
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Your big cortex makes you different from other animals. You can keep building new neural pathways and thus keep fine-tuning your efforts to meet your needs. But man does not live by cortex alone. You need your limbic system to know what’s good for you. Your cortex sees the world as a chaos of raw detail until your limbic system creates the feeling that something is good or bad for you. You may have gotten the idea that your limbic brain is the bad guy and your cortex is the good guy, but it’s more helpful to know how they need each other. Your limbic system needs your cortex to make sense of your pleasure and pain. But your cortex cannot produce happy chemicals. If you want to be happy, you have to get it from your limbic system.
The limbic system cannot process language. When you talk to yourself, it’s all in your cortex. That’s why the limbic system never tells you in words why it activates a happy or unhappy chemical. So you might think, “I’m not feeling that way” just because you didn’t hear yourself verbally decide, for example, “I will be mad at her” or “I am afraid to do that”—but you actually are feeling that way.
Your feelings are unique. You turn on your happy chemicals with unique neural pathways built from your individual experience. That’s why we react differently to the same situation even though we are all reacting with the same basic survival equipment.
Happy moments in your past connected neurons that are there, ready to spark more happy chemicals the next time you’re in similar circumstances. Unhappy moments in your past connected neurons that are there telling you what to avoid.
Each time you have an experience, your senses take in the world and trigger electricity in your brain. That electricity flows in your brain like water flows in a storm—it finds the paths of least resistance. The paths you’ve already built give your electricity a place to flow, and that shapes your response to the experience.
Neurochemicals pave these pathways the way asphalt paves a dirt road. Repetition also paves your pathways. Some of your neural trails develop into superhighways because you’ve activated them repeatedly and neurochemically. For example, a child who gets a lot of respect when she fixes her parents’ computer builds a pathway that expects more good feelings when she does more to help people with computers. So she repeats the behavior, and the pathway builds. We end up with billions of pathways to channel our electricity, and they allow us to create meaning from the flood of inputs reaching our senses.
The trails you have built thus far in your life combine to make up your neural guidance system. The system might not be what you’d design today if you started from scratch, but it guides your reactions to the situations you encounter on a daily basis. Your inner mammal has no reason to doubt its own reactions because they’re built from your actual life experiences. You don’t notice your neural guidance system because you built it without conscious intent. That’s why it’s hard to build new trails: You don’t know how you built the old ones.
Your neural pathways make it easy for you to like some things and dislike others. You may find yourself liking things that are not especially good for you and fearing things that actually are good for you. Why would a brain that evolved for survival build such quirky circuits?
Because we’re designed to store experiences, not to delete them. Most of the time, experience holds important lessons. It helps you go toward whatever helped in the past and avoid whatever hurt. But the pathways of past experience can also mislead. They can lead you to avoid hurts that are long gone, or to seek too much of a good thing. For example, you might avoid math because a kid laughed at you in math class long ago, or you might overindulge in pizza because your parent showed kindness while sharing a pizza long ago.
Your human cortex can adjust your old circuits with new inputs: You can tackle math or resist pizza. But your old circuits are very efficient. You tend to rely on them because the world overwhelms you with information and your superhighways help it flow so well.
But those superhighways don’t always take you where you want to go. Sometimes they lead you to unhappy chemicals just when you were hoping to feel good. You can enjoy more happy chemicals if you blaze new trails through your jungle of neurons. It may be harder than you expect, but it’s easier when you know your equipment.
When you were young, you built new circuits easily. In adulthood, building a new circuit is as hard as slashing through a dense rainforest. Every step requires huge effort, and the new trail you worked so hard for disappears into the undergrowth if you don’t use it again soon. All this slashing may feel like a waste of time when you already have a network of superhighways to use instead.
Your neurons have difficulty sending electricity down a path you’ve never activated before. Each time a pathway is activated, it fires more easily. Repetition develops a neural trail slowly, the way a dirt path hardens from years of use. So how can you build new pathways? The answer is simple: Feed your brain new experiences again and again. Repetition will build the circuits you want. No one can build them for you, and you cannot build them for someone else. This book helps you select new experiences that stimulate happy chemicals, and repeat them until they surge with electricity. You can feel good in ways that are good for you.
You might wish to escape unhappiness forever, but it’s useful to know that unhappy chemicals are as essential to your survival as happy chemicals. Your brain needs unhappy chemicals to call attention to threats and obstacles, just as it needs happy chemicals to call attention to opportunities. You are designed to survive by seeking happy chemicals and avoiding unhappy chemicals. You are not designed for shortcuts that eliminate the seeking and avoiding. Let’s see how these shortcuts can cause a vicious cycle.
The quest for good feelings is nature’s survival engine. Animals seek food to relieve the bad feeling of hunger. They seek warmth to relieve the bad feeling of cold. Happy chemicals start flowing before a mammal even eats or warms up because the mammal brain turns them on as soon as it sees a way to meet a need. The human brain does this with the added boost of a cortex that makes long chains of associations. We avoid hunger by planting food and avoid chill by stocking fuel. We anticipate bad feelings in order to prevent them. But unhappy chemicals persist no matter how well you meet your needs, because your survival is threatened as long as you’re alive.
A mammal risks getting eaten by a predator when it forages for food. It risks social conflict when it seeks a mate, and it risks genetic annihilation if it avoids that conflict entirely. The mammal brain never stops scanning for potential threats. When you’re safe from physical threats, your brain scans for social threats. Mammals survive because the bad feeling of cortisol alerts you in time to avoid potential threats.
Cortisol communicates pain and the expectation of pain. It motivates you to do whatever it takes to make the bad feeling stop. When a lunching gazelle smells a lion, cortisol motivates it to run even though it would rather keep eating. Gazelles survive because smelling a lion feels worse than hunger. Our ancestors survived because cortisol directed their attention to one threat after another.
When your cortisol surges, you respond by noticing what it’s paired with. It could be low blood sugar, or the scent of danger, or social isolation. Life experience builds myriad circuits that light up when your cortisol turns on. Sometimes the solution is obvious, like pulling your hand off a hot stove. But often, you’re not sure what triggered the alarm. You don’t know how to make it stop, yet it feels like something awful will happen if you don’t “do something” immediately. For example, let’s say you have a bad feeling about your boss while sitting at your desk in your office. You want to make that feeling go away because cortisol annoys you until you do something to make it stop. But you’re not sure what started it or how you can relieve it. You do know, from life experience, that doughnuts make you feel good. Doughnuts trigger happy chemicals because fat and sugar are scarce in nature. The good feeling distracts you from the bad feeling, which makes it seem like the threat is gone for the moments you are eating the doughnut. Consciously, you know the doughnut hasn’t fixed your problems, but happy chemicals are molecules that pave a neural pathway. The next time you feel bad about your boss, electricity trickles to the thought of eating a doughnut. If you eat one, you build the connection. You still know the doughnut doesn’t solve your problem and in fact could make it worse. But going with the flow gives you a sense of safety for that moment. When the “do something” feeling strikes, your brain builds the idea that eating a doughnut is doing something.
It would be nice to stop cortisol with permanent solutions to every problem. But that cannot happen because disappointment triggers cortisol too. When a lion loses sight of the gazelle she was stalking, her cortisol turns on. When a monkey can’t crack open the nut he is working on, his cortisol turns on. Your cortisol helps you make course corrections on the path to meeting your needs. Cortisol alerts you when Plan A doesn’t work.
When Plan A works, alas, the happy chemicals don’t last. To get more, you have to do more. That is how a brain keeps prodding a body to do what it takes to keep its DNA alive. Happy chemicals get reabsorbed and your awareness of survival threats resumes. A “do something” feeling gets your attention when you’re not distracted by happy chemicals. As you look for ways to relieve it—fast—easy happy-chemical activators may tempt you.
“Everything I like is illegal, immoral, or fattening.” The old saying has some truth to it because everything that triggers fast, easy happy chemicals has side effects. Good feelings were naturally selected because of their side effects. Food evolved to feel good because that motivates a body to do what it takes to find nutrition. Sex evolved to feel good because that motivates a body to do what it takes to find a mate. The side effects of food and sex were desirable in a world of scarcity. We did not evolve to get an instant high from food and sex in every moment. Seeking a constant high can lead to a vicious cycle.
Happiness happens when these chemicals are triggered.
Your triggers depend on the neural circuits you built in the past.
Unhappy chemicals are always being triggered too.
Happy chemicals distract you from the unhappy ones.
The good feeling tempts you to activate a circuit again and again.
Side effects result, and trigger more unhappy chemicals.
More happy circuits are the answer. Here’s how to build them.
Vicious cycles are everywhere:
Each of these behaviors can make you feel good in a moment when you were feeling bad. That gives you a nice sense of conquering a threat, so you repeat the behavior. Over time, a neural superhighway develops, and the behavior seems to light up effortlessly. But side effects accumulate and trigger unhappy chemicals. Now you’re even more motivated to trigger happy chemicals in the way you expect them to work. But it’s like driving with one foot on the accelerator and one on the brake—the same behavior triggering both happiness and unhappiness.
You can stop a vicious cycle in one instant. Just resist that “do something” feeling and live with the cortisol. This is difficult to do because cortisol screams for your attention. It didn’t evolve for you to sit around and accept it, after all. But you can build the skill of doing nothing during a cortisol alert, even as it begs you to make it go away by doing something. Waiting gives your brain a chance to activate an alternative. A virtuous circle starts in that moment.
Seizing the moment is easier if you have an alternative circuit ready. Your new circuit may feel awkward at first. It lacks the zip of electricity you’ve relied on for the sense that you know what’s going on. Resisting an old circuit can make you feel like you’re threatening your own survival when you’re doing precisely the opposite.
The pain of resisting a habit eases once a new habit forms. You can do that in forty-five days if you repeat a new thought or behavior every day without fail. If you miss a day, start over with Day One. The new choice will not make you happy on Day One, and it may not make you happy on Day Forty. Even on Day Forty-Five, it cannot trigger happy chemicals constantly. But it will invite enough electricity to free you from a vicious cycle.
It’s not easy being a mammal with a big cortex. We have enough neurons to imagine things that don’t exist instead of just focusing on what is. This gives us the power to imagine solutions before it’s too late. We improve our lives, but we also stimulate bad feelings. To feel better, we imagine a “better world,” where happiness flows effortlessly and bad feelings are eradicated. But this is not a realistic expectation with the brain we have. Your brain only releases happy chemicals when you take steps toward meeting needs. You can end up in a vicious cycle if you focus on the short-run good feeling of an imagined world and neglect the reality of the world you live in.
It’s easy to see vicious cycles in others. That’s why we’re tempted to take charge of other people’s happiness. But you cannot reach into someone else’s brain and make new connections for them, nor can they do that for you. If you focus on other people’s brains, you may fail to make them happy and fail to make yourself happy. Each person must manage his or her own limbic system.
Modern society is not the cause of vicious cycles. Our ancestors had variations of their own. For example, they made human sacrifices to relieve threatened feelings, and when they felt bad again, they made more sacrifices. We have developed better ways to feel good, but side effects still plague us, so we strive to do better.
You’ve probably heard that love is the key to happiness, but it’s useful to know how happy chemicals create that feeling. Love is a huge surge of happy chemicals because it’s hugely relevant to the survival of your genes. You’re not thinking about your genes when you’re in love, but your genes are inherited from people who did what it took to reproduce successfully. Brains that motivate reproductive behavior end up making more copies of themselves. Sex is only a small part of the story. Everything from competing for healthy mates to nurturing healthy offspring is relevant to what biologists call “reproductive success.” Love motivates all of these behaviors.
You may find it hard to link your loving feelings to natural selection. But in the animal world, it’s easy to see how brain chemicals shape mating behavior. The mammal brain is very focused on reproductive success. Once a mammal’s immediate survival needs are met, its thoughts turn to the survival of its genes. Animals are surprisingly picky about their mates. For example, every species avoids in-breeding in one way or another. Without conscious concern for genes, neurochemicals motivate alternative choices. Brains that produced in-breeders died out, while brains that motivated alternative mating choices flourished.
Each happy chemical rewards love in a different way. The familiar joys and sorrows of love are curiously equivalent to the impulses of dopamine, oxytocin, serotonin, endorphin, and cortisol. (The sex hormones, like testosterone and estrogen, are central to the feelings we associate with love, but they are outside the scope of this book because they do not trigger the feeling of happiness. They mediate specific physical responses instead.)
Dopamine is stimulated by the “chase” aspect of love. It’s also triggered in a baby who hears his mother’s footsteps. Dopamine is the brain’s signal that a need is about to be met. Female chimpanzees are known to be partial to males who share their meat after a hunt. Protein is scarce in the rainforest and females need a lot of it for gestation and lactation, so meat is a great dopamine stimulator. For humans, finding “the One” makes you high on dopamine. However you define what you seek, dopamine excites you when you approach it.
Oxytocin is stimulated by touch and by trust. In animals, touch and trust go together. Apes only allow trusted companions to touch them because they know from experience that violence can erupt in an instant. In humans, everything from holding hands to feeling supported triggers oxytocin. Orgasm does too. Sex triggers a lot of oxytocin at once, yielding a lot of social trust for a very short time. Holding hands stimulates a small amount of oxytocin, but when repeated over time, as in the case of an elderly couple, it builds up a circuit that easily triggers social trust. Childbirth triggers a huge oxytocin spurt in mammals, both mother and child. Nurturing other people’s children can stimulate it too. Friendship bonds stimulate oxytocin, and they also promote reproductive success. Monkeys and apes with more social alliances have more surviving offspring, and adolescents clearly desire individuals with more social alliances too. Oxytocin is related to love in so many ways that it is often called the bonding hormone or the cuddle chemical.
Serotonin is stimulated by the status aspect of love—the pride of associating with a person of a certain stature. You may hate thinking of your love in this way, but you can easily see it in others. Animals with higher status in their social groups have more reproductive success, and natural selection built a brain that rewards you with the good feeling of serotonin when you raise your status. This may be hard to believe, but research on a huge range of species shows tremendous energy invested in the pursuit of status. Social dominance leads to more mating opportunity and more surviving offspring—and it feels good. We no longer try to survive by having as many offspring as possible, but when you receive the affection of someone you perceive as important, your serotonin surges.
Endorphin is stimulated by physical pain, but you get a bit from laughing and crying too. Lovers are known for laughing together, and it’s interesting to know that they are stimulating each other’s endorphin. Crying is associated with love too, alas. Confusing love and pain is a bad survival strategy, but endorphin pathways may explain some people’s tolerance for painful relationships.
Cortisol plays an important role in reproductive success, too. It makes you feel bad when you lose love, which promotes survival by helping you move on. If you remained attached to a person who is not available to you, your genes would be doomed. Cortisol helps your brain rewire to associate your old lover with negative rather than positive expectations, so you start seeking love elsewhere. We wish lost love wouldn’t feel so bad, but it’s interesting to know that the bad feeling has a valuable function.
In animals, it’s easy to see how bad feelings promote love:
Love feels bad for a subtle reason that’s widely overlooked. We are born helpless and need love to survive. The first experience in each brain is the sensation of needs that you cannot meet for yourself. You feel good when others meet your needs, and you come to expect that. Alas, we must transition from childlike dependence to mature independence. That can feel like a survival threat to the part of your brain that expects to be taken care of. This motivates people to find adult love, and that keeps our genes alive. But the interdependence of mature love never measures up to the dependence of your brain’s first circuits.
Love feels good because it’s hard to keep your DNA alive in the state of nature. Survival rates are low and mating opportunities are harder to come by than you might expect. Without a huge effort, your genes would get wiped off the face of the earth. Now, I know you are not thinking about your genes, and animals aren’t either. But every brain is inherited from individuals who did what it took to reproduce. Love makes it feel good.
There is no free love in nature. Every species has preliminary qualifying events before mating. Creatures work hard for any mating opportunity that comes their way. Good feelings reward you for pursuing the quest. Bad feelings warn you that your genes will be annihilated if you don’t get busy. Something as small as failing to get a smile from the person you smile at can trigger surprising neurochemistry because your brain relates it to the survival prospects of your genes.
In modern times, people want romantic love throughout their lives, but expectations were different in the past. Children started coming as soon as you had sex, and they cried if you didn’t keep feeding them. You were too busy to worry about romantic love. If you lived to middle age, you had grandchildren with more needs. People had the same basic neurochemistry, but without birth control they were more focused on immediate survival. Today, we explore many ways to trigger happy chemicals, but you must keep working to keep them coming. Each burst of a happy chemical is metabolized in a short time so you’re always looking for ways to get more. Maybe that’s why love songs are always popular. They stimulate brain chemicals without the messy side effects.
And now let’s meet those happy chemicals in more detail.