Habits of a Happy Brain Read online

  Mammals live in herds and packs and troops because there’s safety in numbers. If they are separated from their group mates, their oxytocin falls and they feel bad. A herd animal panics when it can’t see at least one of its group. When it rejoins them, a surge of oxytocin relieves the cortisol.

  Oxytocin and Reproduction

  Mammals take the risk of leaving their group when it promotes reproduction. Young mammals transfer to a new troop at puberty to improve mating opportunities. (Depending on the species, either the males or the females disperse at puberty.) A mother mammal leaves her group to search for a lost child or to give birth. Reproductive behaviors trigger more oxytocin than mere companionship, which motivates a mammal to leave the group to promote its genes.

  When a mammal gives birth, her oxytocin surges. This motivates her to guard the newborn constantly in addition to facilitating labor and lactation. Oxytocin spikes in the newborn brain too, so a young mammal clings to its mother without comprehending the danger of leaving her. When the birth process is over, more oxytocin is stimulated by holding or licking. This paves neural pathways that facilitate the flow of oxytocin in similar settings. Bonds of attachment are a buildup of oxytocin circuits. Over time, attachment extends from the mother to the herd or pack or troop.

  Touch triggers oxytocin. Primates are often seen running their fingers through a troop mate’s fur to remove debris. Oxytocin makes it feel good to both the giver and the receiver. Monkeys and apes invest a lot of time grooming others, and it appears to establish social alliances. Researchers find that monkeys and apes with more social alliances get better mating opportunities and have more surviving offspring. When there’s a conflict in a troop, primates tend to aid the individuals they groom with. Social alliances can entangle you in trouble, but oxytocin makes it feel good.

  Trusting the Group vs. Trusting Yourself

  A herd only protects you if you follow the crowd and run when they run. If you insist on seeing the lion for yourself before you run, you are less likely to survive. Natural selection built a brain that can trust the judgment of others. But herd behavior has a downside that’s obvious to humans. We worry about jumping over cliffs when the other lemmings jump. We worry about group-think and gangs and codependence. We override our herd impulses and strike out on our own. But we often feel like a lamb among lions because of our urge for oxytocin.

  Reptiles have no warm and fuzzy feelings toward other reptiles. They stay alone in their vigilance instead of distributing the burden among many eyes and ears. A lizard never trusts other lizards. Its chemical equivalent of oxytocin is only released during mating and egg laying.

  Reptiles strike out on their own the moment they’re born. Instead of relying on parental care, a young lizard starts running the instant she hatches from her shell. If she doesn’t run fast enough, a parent eats her—the better to recycle the energy into another sibling instead of letting a predator get it. Fish don’t even wait for their eggs to hatch. They swim off to pursue other interests the moment their eggs are fertilized. Plants send their seed into the wind without ever knowing if it grows into mighty oaks.

  Mammals, on the other hand, bond with their child because oxytocin receptors prepare us to feel good about it. (Birds have some parental care too, and they have a molecular equivalent of oxytocin.) Parental attachment revolutionized the biology of the brain. It became possible for mammals to be born without survival skills and to learn from life experience instead. Unlike reptiles, fish, and plants, which are born with all necessary survival knowledge, mammals are born fragile and stupid. The mammal brain does not fully develop in the safety of the uterus or egg. It develops by interacting with the world around it. A mammal needs protection while its brain is still developing, but this investment leads to a huge advantage: Each generation wires itself to survive in the world it actually lives in rather than the world of its ancestors.

  Brain Size Matters

  The smaller an animal’s brain, the more it relies on prewired survival skills. That prewired brain is adapted to a specific ecological niche, and it quickly dies outside that niche. The bigger an animal’s brain, the more it builds survival skills from life experience. A big brain makes connections instead of being born with connections. The larger a creature’s brain, the longer it remains helpless after birth. It takes time to fill a brain with useful connections.

  A big brain creates a huge survival dilemma because a fragile newborn is easily eaten by predators. A big-brained baboon or elephant cannot birth hundreds of offspring for a few to survive, the way a small-brained snake or lizard does. A warm-blooded, big-brained infant is hard to gestate, so a mother can only make a few in her lifetime. If she loses them to predators, her genes are wiped out. So she does her darnedest to keep every single one alive.

  Oxytocin and Attachment

  But the more you invest in each child, the more you lose if it dies. Attachment is what makes this strategy work. Momma mammals guard each newborn constantly, and herds help them out. When a predator snatches a young mammal, the mother loses a chunk of her lifetime reproductive capacity, but oxytocin keeps motivating attachment.

  For most of human history, people spent their lives in the network of attachments they were born into. They might have transferred to a new group to mate, but such transfers were otherwise limited. Today, lasting attachments are less preferred and often disparaged. Without them, however, we feel like something is wrong. We don’t know why, but we long for the place where “everybody knows your name.” Or the crowded sports arena or concert hall where thousands of people act on the same impulse. Or the political group that shares your anger. Or the online forum that welcomes your comments. These things feel good because social alliances stimulate oxytocin. Of course, they are only brief moments of trust—small squirts that will soon pass. And that’s why the brain is always looking for a chance to stimulate more.

  EXERCISE: WHEN DO YOU FEEL OXYTOCIN?

  Oxytocin is the pleasure of letting down your guard near those you trust. It’s not the conscious decision to trust, but the physical feeling of safety you get from proximity to trusted others. Oxytocin flows in a gazelle surrounded by its herd and a monkey having its fur groomed. Social alliances promote survival, and mammals evolved a brain that makes it feel good. A human brain can abstract, so we can enjoy the feeling of social support without others being physically present. Our oxytocin pathways build from life experience. We mammals surge with oxytocin at birth, which builds our core attachment circuits. We wire ourselves to trust whatever we experience while our oxytocin is flowing. That’s how a young mammal transfers its attachment from its mother to its herd. Humans often leave the herd we grew up in, but our brains still crave oxytocin. Notice the good feeling stimulated by the following opportunities to lower your guard:

  Someone protects or supports you

  You protect or support someone

  The touch of someone you trust

  The physical proximity of someone you trust

  Coping with Betrayed Trust

  Alas, the good feeling of social trust sometimes leads to the bad feeling of betrayed trust. Since we avoid bad feelings, we make careful decisions about when to trust and when to withhold trust. Primates have enough neurons to be choosy about their friends. Monkeys and apes form individualized attachments instead of all-or-nothing bonds to a troop. With each social interaction, they update their circuits with oxytocin or cortisol. Over time, you “know who your friends are” because your neurochemicals react to individuals as “good for your survival” or “bad for your survival.”

  OXYTOCIN AND LONG-TERM BONDS

  Monogamy is rare in the mammal world, though it appears in species with high oxytocin. Most mammals bond with foraging partners rather than sex partners. You might have mixed feelings about the people you eat with and work with. You might not trust them sometimes and even wonder why you put up with them. But when you leave them, your oxytocin falls and your mammal brain tells you that something is wron
g.

  Primates are always negotiating their social alliances. This is easy to see in your daily life, when you interact with family members, friends, coworkers, or neighbors. You may find it annoying when you see others do it. But when you seek support, you feel like you are just trying to survive. Social alliances transform threatened feelings into safe feelings thanks to oxytocin.

  Meet Your Serotonin

  Getting respect feels good because it triggers serotonin. The good feeling motivates you to seek more respect, and that promotes survival. You may feel sure that you don’t think this way, but you can easily see this dynamic in others. In the animal world, getting respect clearly promotes an individual’s DNA. They’re not thinking about genes, of course. They seek social dominance because serotonin makes it feel good. They avoid conflict because it’s linked to pain. The mammal brain is always looking for ways to enjoy the good feeling of serotonin without the bad feeling of pain.

  The Connection Between Dominance and Serotonin

  Each mammal species has gestures that signal dominance and submission. A dominance gesture signals the intent to control food or mating opportunity. A submission gesture protects an individual from the pain of conflict with stronger individuals. Animals only fight when both individuals believe they are stronger. Conflict is usually avoided because animals are skilled at assessing their relative strength, and the weaker individual submits to avoid harm.

  In the human world, we shift fluidly between the dominant and subordinate position in the course of each day. We sustain goodwill by taking the lead sometimes and ceding control at other times. You can say no one should ever dominate, but if you collide in a doorway and say “after you,” but the other person says “after you,” someone must act or you’ll be in that doorway forever. Maybe you will go last by insisting harder, and then feel superior about it. That’s your mammal brain’s quest for serotonin.

  Mammals seek the one-up position because serotonin makes it feel good. One study showed this by separating an alpha vervet monkey from his troop with a one-way mirror. (An alpha is the individual to whom group mates routinely defer.) The alpha monkey made the dominance gestures typical of his species, but his subordinates did not respond with the expected submission gestures because the one-way mirror blocked their view of him. The alpha got agitated and his serotonin level fell. Each day the experiment continued, his serotonin kept dropping and his agitation grew. He needed their submission to keep up his serotonin.

  Serotonin and Survival

  All living creatures have serotonin, even amoeba. One-celled animals use serotonin in a way that’s curiously relevant to us. We humans have more serotonin in our digestive system than we have in our brains. An amoeba is too small to have separate digestive and nervous systems, so it uses serotonin in a dual way that explains everything. Serotonin signals the amoeba’s body to move toward food and get ready to digest it. The mechanism is astonishingly simple. An amoeba constantly forages and scans for danger by letting tiny amounts of water pass through its cell membrane. If the water sample shows a high concentration of foreign material, the amoeba interprets that as danger and it wiggles off in a random direction. If the sample contains a low level of foreign material, the amoeba perceives a good feeding opportunity and releases serotonin. That straightens its tail so it forges straight ahead, and it turns on its digestive juices. Serotonin is the sensation that it’s safe to go ahead and meet your needs.

  In mammals, serotonin is the good feeling of having secure access to food or other resources. The stronger mammals in a herd or pack or troop typically dominate food and mating opportunities. This may conflict with one’s pristine view of nature, but close observation of countless species shows that each has its way of competing for resources. Much of the time, animals are having food fights, battling over mating opportunities, and doing everything possible to get their offspring ahead. Humans strive to curb these impulses, but we’ve inherited a brain that makes social dominance feel good. We scan for ways to enjoy the good feeling of social importance without the bad feeling of conflict.

  Imagine a piglet born in a litter of sixteen to a mother who has twelve teats. Each piglet struggles for nourishment from the moment of birth. Complex decisions are required. If a piglet doesn’t struggle it could starve to death, but if it struggles too much, it may get injured in conflict or simply consume more energy than it takes in. Serotonin helps a piglet find the level of assertion that’s just right. Each time a piglet succeeds at dominating another, it gets a squirt of serotonin. That motivates it to seek more of the good feeling, and the extra nourishment helps it prevail. But it fails sometimes, and its serotonin falls. That motivates it to submit and conserve energy. Serotonin promotes survival whether it’s up or down by balancing energy expenditure with food intake.

  The piglet’s cortisol spikes if it’s seriously underfed. That motivates aggression, which helps it get food. Aggression is different from social dominance, because cortisol feels bad while serotonin feels good. Social dominance is the calm, secure expectation that you will get what you need. Cortisol is the sense that something awful will happen if you don’t act now.

  When a piglet has extra energy, it strives to dominate a teat and keep others away. If it succeeds, it strives for a better teat—one closer to the mother’s heart. The top teat brings more nutrition and more warmth than the hind teats. Researchers are still debating this, but farmers have observed it for centuries.

  Mother Pig does not intervene in this conflict. The siblings sort it out for themselves by the time they are a few days old. Each piglet learns from the experience of pleasure and pain. Each brain builds expectations that tell it when to forge ahead to meet its needs and when to hold back to avoid pain. Soon the piglets will be out foraging for their own food, and then start competing for mating opportunities.

  Intra-Group Conflict

  Every brain longs for the good feeling of serotonin, but the motivation is easier to see in others and can be difficult to see in yourself. The point is not that you should push your way to the best teat. The point is that your brain constantly monitors your access to resources. When access looks secure, you feel good for a moment, and then you look for ways to make it more secure. You may get annoyed when you see others trying to secure their position. But when you do it, you think, “I’m just trying to survive.”

  Securing resources is tricky for creatures that live in groups. A solitary reptile can just lunge at food without worrying about others. If a group-living mammal lunged at food, it might crash into a bigger, stronger individual who would attack it. Avoiding injury promotes survival more than any one bite of food. So the impulse to compare yourself to others and decide whether you’re stronger or weaker is more pressing than the impulse to eat. When a mammal sees that it’s weaker, it restrains itself until the other has eaten. When a mammal sees that it’s stronger, its serotonin surges and it lunges at food.

  I am not saying we should dominate the weak. I am saying we should recognize our own evolutionary urge to make social comparisons and come out on top. Young mammals quickly learn that stronger individuals will bite them if they’re in the way of desirable resources. The pain of being bitten wires a youth to hold back. You may call it “cooperation” when you see an animal hold back, but the animal wants its chance to eat and reproduce. It is not lyricizing about cooperation. It is scanning for safe opportunities to go for it.

  MALE VS. FEMALE SURVIVAL STRATEGIES

  Each gender seeks dominance in ways that best promote its DNA. In most species, females invest so heavily in each offspring that their genes are best served by enhancing the survivability of her young. A male’s reproductive success is often served by maximizing mating opportunities. Within these strategies, both genders dominate and submit to meet their needs.

  Animals can’t save money for a rainy day. The only way they can put something aside for the future is to invest today’s extra energy into social power that can help them survive tomorrow. That�
�s why each mammalian herd or pack or troop has its status hierarchy. The organization is not conscious, of course. Each individual simply remembers whom they fear and whom they trust, and a hierarchy emerges organically. Cortisol tells a mammal to hunch down in self-defense in the face of a stronger group mate. Serotonin tells a mammal to swell with pride (or air, depending on how you look at it) when it is strong enough to get respect and meet its needs.

  A cow that pushes her way to the center of the herd is safer from predators than a cow near the edge of the herd. The pushy cow improves her chances of living to reproduce and keeping her young alive. Bulls typically avoid the herd until mating time, when they ferociously battle other males for admission. The most dominant bull pushes his way to the center of the herd, where he meets and inseminates the most dominant cows. In each species, social dominance promotes reproductive success in one way or another. I am not advocating such behavior, simply recognizing the human challenge of trying to feel good while avoiding conflict.

  Are Animals Really Selfless?

  You may have heard that animals are altruistic. There’s a demand for evidence that nature is good, and researchers tend to supply “studies” that meet the demand. In the name of science, hundreds of trials are done, and instances that can be construed as altruism are reported. The illusion of animal altruism is often built on highly artificial laboratory scenarios. In the wild, animals will snatch food from the mouths of juveniles who dare to go for it, but that’s not reported in the news.