Prior to playing this trust game, using a double-blind research design, participants received either oxytocin or an inert placebo by nasal spray. The effect of this single intranasal blast of oxytocin on the outcome of the trust game was dramatic: The number of investors who trusted their entire allotment to their trustee more than doubled. Interestingly, related research using this same trust game showed that the mere act of being entrusted with another person’s money raises the trustee’s naturally occurring levels of oxytocin, and that the greater the trustee’s oxytocin rise, the more of his recent windfall he sacrificed back to the investor. The neuropeptide oxytocin, then, steers the actions of both the investor and the trustee, shaping both trust and reciprocity. These findings suggest that through synchronous oxytocin surges, trust and cooperation can quickly become mutual.
Since the original study on oxytocin and the trust game was published in Nature in 2005, variations on it have abounded. We now know, for instance, that oxytocin doesn’t simply make people more trusting with money, it also makes them far more trusting—a whopping 44 percent more trusting—with confidential information about themselves. Interestingly, the simple act of sharing an important secret from your life with someone you just met increases your naturally circulating levels of oxytocin, which in turn raises your confidence that you can trust that person to guard your privacy. Thankfully, we also know that oxytocin does not induce trust indiscriminately, making people gullible and therefore open to exploitation. The effects of oxytocin on trust turn out to be quite sensitive to interpersonal cues, like those subtle signs that tip you off that another may be the gambling type or irresponsible in other ways. Rest assured, then, if oxytocin spray were to be aerated through your workplace ventilation system, you’d still maintain your shrewd attunement to subtle signs that suggest whether someone is worthy of your trust or not.
Researchers have since moved on to examine the effects of oxytocin on people’s sensitivities to the subtle social cues that signal whether or not trust is warranted. From this work, I can tell you that, under the influence of oxytocin, you attend more to people’s eyes and become specifically more attuned to their smiles, especially subtle ones. Perhaps because of the closer attention you pay to peoples’ smiles and eyes, you become a better judge of their feelings and view people on the whole as more attractive and trustworthy. You also become particularly sensitized to environmental cues linked to positive social connections—for instance, to words like love and kissing. Researchers who have combined the use of oxytocin nasal spray (versus placebo) with brain imaging have also learned that oxytocin modulates the activity of your amygdala, the subcortical structure deep within your brain linked to emotional processing. Specifically, under the influence of a single blast of oxytocin nasal spray, the parts of your amygdala that tune in to threats are muted, whereas the parts that tune in to positive social opportunities are amplified. Reflecting these negativity-dampening effects, a single shot of oxytocin can also help you glide through stressful social situations, like giving an impromptu speech or discussing a conflict-ridden topic with your spouse. If you were to face these difficulties under the influence of oxytocin, studies suggest, you’d have less cortisol, the so-called stress hormone, coursing through you, and you’d behave more positively, both verbally, by disclosing your feelings, and nonverbally, by making more eye contact and friendly gestures. Related research shows that behaving kindly in these ways also raises your naturally occurring levels of oxytocin, which in turn curbs stress-induced rises in heart rate and blood pressure, reduces feelings of depression, and increases your pain thresholds.
More generally, oxytocin has been cast as a lead character in the mammalian calm-and-connect response, a distinct cascade of brain and body responses best contrasted to the far more familiar fight-or-flight response. Let’s face it, meeting new people can be a little scary at times. Think back to what it was like for you on your first day at a new school or in a new job. You’re suddenly thrown in with people you’d never heard of before. Even if a new person seems friendly, it’s hard to know his true motives. Will he help you? Or will he instead take advantage of you in one way or another? Human greed, after all, runs rampant and can yield all manner of exploitation. Oxytocin appears both to calm fears that might steer you away from interacting with strangers and also to sharpen your skills for connection. As I’ve mentioned, though, oxytocin is far from blind. It indeed heightens your attunement to cues that signal whether others are sincere or not. Through eye contact and close attention to all manner of smiles—and the embodied simulations such visual intake triggers—your gut instincts about whom to trust and whom not to trust become more reliable. Rather than avoid all new people out of fear and suspicion, oxytocin helps you pick up on cues that signal another person’s goodwill and guides you to approach them with your own. Because all people need social connections, not just to reproduce, but to survive and thrive in this world, oxytocin has been dubbed “the great facilitator of life.”
It, too, can jump the gap between people such that someone else’s oxytocin flow can trigger your own. A biochemical synchrony can then emerge that supports mutual engagement, care, and responsiveness.
The clearest evidence that oxytocin rises and falls in synchrony between people comes from studies of infants and their parents. When an infant and a parent—either mom or dad—interact, sometimes they are truly captivated by each other, and other times not. When an infant and parent do click, their coordinated motions and emotions show lots of mutual positive engagement. Picture moms or dads showering their baby with kisses, tickling their baby’s tiny fingers and toes, smiling at their baby, and speaking to him or her in that high-pitched, singsong tone that scientists call motherese. These parents are superattentive. As they tickle and coo they’re also closely tracking their baby’s face for signs that their delight is mutual. In step with their parent’s affectionate antics, these attentive babies babble, coo, smile, and giggle. Positivity resonates back and forth between them. Micro-moments of love blossom.
Of course, not every infant-parent interaction is so rosy. Some pairs show little mutual engagement. Some moms and dads rarely make eye contact with their infants and emit precious little positivity, either verbally or nonverbally. These pairs are simply less attuned to each other, less connected. And in those rare moments when they are engaged, the vibe that joins them is distinctly more negative. They connect over mutual distress or indifference, rather than over mutual affection.
It turns out that positive behavioral synchrony—the degree to which an infant and a parent (through eye contact and affectionate touch) laugh, smile, and coo together—goes hand in hand with oxytocin synchrony. Researchers have measured oxytocin levels in the saliva of dads, moms, and infants both before and after a videotaped, face-to-face parent-infant interaction. For infant-parent pairs who show mutual positive engagement, oxytocin levels also come into sync. Without such engagement, however, no oxytocin synchrony emerges.
Positivity resonance, then, can be viewed as the doorway through which the exquisitely attuned biochemical tendencies of one generation influence those of the next generation to form lasting, often lifelong bonds. Knowing, too, that oxytocin can ebb and flow in unison among non-kin—even among brand-new acquaintances just learning to trust each other—micro-moments of love, of positivity resonance, can also be viewed as the doorways through which caring and compassionate communities are forged. Love, we know, builds lasting resources. Oxytocin, studies show, swings the hammer.
This core tenet of my broaden-and-build theory—that love builds lasting resources—finds support in a fascinating program of research on . . . rodents. It turns out that rat moms and their newborn pups show a form of positive engagement and synchrony analogous to that of human parents with their infants. Sensitive parenting in a rat mom, however, is conveyed by her attentively licking and grooming her newborn pups. When a rat mom licks and grooms her pup, it increases the pup’s sensitivity to oxytocin, as indicated, f
or instance, by the number of oxytocin receptors deep within the pup’s amygdala, as well as within other subcortical brain regions. Sure enough, these well-groomed—or I dare say well-loved—rat pups grow up to have calmer demeanors; they’re less skittish, more curious. The researchers can be certain that it’s the experiences of loving connection that determine the brain and behavioral profiles of the next generation (that is, their oxytocin receptors and calm demeanors)—and not simply shared genes—because cross-fostering studies show the same patterns of results. That is, even when a rat mom raises a newborn pup that is not her own, her maternal attention still forecasts that pup’s brain sensitivity to oxytocin and whether it grows up to be anxious or calm.
Touring Vagus
Who you are today is also shaped by the third biological character that I want you to meet: your tenth cranial nerve. This key conduit connects your brain to your body and is also called your vagus nerve (sounds like Vegas, as in Las Vegas). It emerges from your brain stem deep within your skull and, although it makes multiple stops at your various internal organs, perhaps most significantly it connects your brain to your heart. You already know that your heart rate shoots up when you feel insulted or threatened—registering the ancestral fight-or-flight response—but you may not know that it’s your vagus nerve that eventually soothes your racing heart, by orchestrating (together with oxytocin) the equally ancestral calm-and-connect response.
Keeping in mind that love is connection, you should know that your vagus nerve is a biological asset that supports and coordinates your experiences of love. Completely outside of your awareness, your vagus nerve stimulates tiny facial muscles that better enable you to make eye contact and synchronize your facial expressions with another person. It even adjusts the minuscule muscles of your middle ear so you can better track the other person’s voice against any background noise. In these exquisitely subtle yet consequential ways, your vagus nerve increases the odds that the two of you will connect, upping your chances for positivity resonance.
Scientists can measure the strength of your vagus nerve—your biological aptitude for love—simply by tracking your heart rate in conjunction with your breathing rate. Specifically, I can look at the degree to which your heart rate, as tracked by sensors placed on your lowest ribs, is patterned by your breathing rate, as revealed by an expandable bellows that encircles your rib cage. This pattern is called vagal tone. Like muscle tone, the higher your vagal tone, the better.
In addition to putting the brakes on the big jumps in your heart rate that may be caused by stress, fear, or exertion, your vagus nerve also increases the routine efficiency of your heart, beat by beat, or more precisely, breath by breath. The human heart rate tends to run fairly high, as if we’re always on guard for the next danger that might be hidden around the corner. When you’re breathing in, a fast heart rate is an efficient heart rate. After all, each successive heartbeat during an in-breath circulates more freshly oxygenated blood throughout your brain and body. Yet when you’re breathing out, a fast heart rate is not all that helpful because your supply of freshly oxygenated blood is waning. Here again, your vagus nerve steps in to help out. It can very gently apply the brake on your heart while you exhale, slowing your heart rate down a small degree. In turn your vagus nerve can gently let up on the brake while you inhale, letting your naturally high heart rate resume to grab all the oxygenated blood that it can get. This creates a subtle yet healthy pattern of cardiac arrhythmia: Your heart rate speeds up a bit when you inhale and slows down a bit when you exhale. This is the pattern that reflects your vagal tone, the strength or condition of your vagus nerve. It characterizes the nimbleness with which your primitive, nonconscious brain holds the reins on your galloping heart.
I give you this quick tour of vagus because this conduit within you, between your brain and your heart, has a story to tell about how attuned you are to sources of love in your midst. It even makes a quiet prediction about what illnesses may beset you and how long you’re likely to live. Your biological propensities for love and health, as we shall see, are intimately intertwined. Measured at rest, vagal tone also tends to be extraordinarily stable over time. For most people, it remains roughly the same year after year, rhythmically channeling them toward loneliness or social prosperity, sickness or health.
That’s because people with higher vagal tone, science has shown, are more flexible across a whole host of domains—physical, mental, and social. They simply adapt better to their ever-shifting circumstances, albeit completely at nonconscious levels. Physically, they regulate their internal bodily processes more efficiently, like their glucose levels and inflammation. Mentally, they’re better able to regulate their attention and emotions, even their behavior. Socially, they’re especially skillful in navigating interpersonal interactions and in forging positive connections with others. By definition, then, they experience more micro-moments of love. It’s as though the agility of the conduit between their brains and hearts—as reflected in their high vagal tone—allows them to be exquisitely agile, attuned, and flexible as they navigate the ups and downs of day-to-day life and social exchanges. High vagal tone, then, can be taken as high loving potential. Indeed, this is what doctoral student Bethany Kok and I have found: Compared to people with lower vagal tone, those with higher vagal tone experience more love in their daily lives, more moments of positivity resonance.
You might now be wondering whether you’re one of the lucky ones blessed with high vagal tone. If you are, that’s great. Yet even if you’re not advantaged with high vagal tone today, the latest science gives plenty of reason for hope. Just as you can build muscle tone through regular physical exercises, you can build vagal tone through regular emotional exercises of the kind I share in part II of this book. The key, once again, is the power of love.
My students and I work together in what I call the PEP Lab, or the Positive Emotions and Psychophysiology Laboratory. Not long ago, we conducted an experiment on the effects of learning the ancient mind-training practice of loving-kindness meditation. Our study participants visited the PEP Lab at the University of North Carolina one by one, and we measured their vagal tone while they sat and relaxed for a few minutes. At the end of this initial laboratory testing session, we instructed participants how to log on to the study website each evening to record their emotions and social connections of the day. A few weeks later, by random assignment, we determined which participants would learn loving-kindness meditation and which would not. All would continue to monitor their day-to-day emotions and social connections using our study website. Months later, weeks after the meditation workshop ended, one by one we invited all participants back to the PEP Lab, where we again measured their vagal tone under the same resting conditions as before.
In May 2010, I had the immense honor of presenting the results of this experiment directly to His Holiness the Fourteenth Dalai Lama. A handful of scientists were invited to a private meeting to brief His Holiness on their latest discoveries about the effects of mind-training. After briefly describing to His Holiness the functions of the vagus nerve and the concept of vagal tone, I shared what my team and I had discovered in this most recent study: that vagal tone—which is commonly taken to be as stable an attribute as your adult height—actually improves significantly with mind-training. Here is your evidence-based reason for hope: No matter what your biological capacity for love is today, you can bolster that capacity by next season.
For it was those study participants who had been assigned at random to learn loving-kindness meditation who changed the most. They devoted scarcely more than an hour of their time each week to the practice. Yet within a matter of months, completely unbeknownst to them, their vagus nerves began to respond more readily to the rhythms of their breathing, emitting more of that healthy arrhythmia that is the fingerprint of high vagal tone. Breath by breath—loving moment by loving moment—their capacity for positivity resonance matured. Moreover, through painstaking statistical analyses, we pinpointed that
those who experienced the most frequent positivity resonance in connection with others showed the biggest increases in vagal tone. Love literally made people healthier.
Upward Spirals Unleashed
It’s time now to step back from isolated scientific findings and take in the big picture. Recall that your body’s positivity resonance operates within a much larger system. Along with love and all the other positive emotions, this system also includes your enduring resources—your physical health, your social bonds, your personality traits, and your resilience. Having assets like these certainly makes life easier, and more satisfying. In addition, though, such resources also serve as booster shots that increase the frequency and intensity of your micro-moments of positivity resonance. Love built those resources in you, and those resources in turn boost your experiences of love. This is not a simple case of cause and effect. The causal arrow instead runs in both directions at once, creating the dynamic and reciprocal causality that drives self-sustaining trajectories of growth. Through love, you become a better version of yourself. And as your better self, you experience love more readily. It is in this dance between your enduring resources and your micro-moments of love that life-giving upward spirals are born.
Looking out from this more encompassing vantage point, let’s revisit the scientific findings I shared with His Holiness the Dalai Lama. By learning how to self-generate love, you can raise your vagal tone. And with higher vagal tone, your attention and actions become more agile, more attuned to the people in your midst. You become better able to forge the interpersonal connections that give rise to positivity resonance. Through vagal tone, then, love begets love.
Likewise, evidence suggests that positivity resonance raises your oxytocin levels. And under the influence of oxytocin, you grow calmer, more attuned to others, friendlier, and more open. Here, too, your skills for forging connections sharpen, which increases your ability to cultivate positivity resonance. Through oxytocin as well then, love begets love.
Love 2.0: How Our Supreme Emotion Affects Everything We Feel, Think, Do, and Become Page 6