Free Love 2.0 by Barbara L. Fredrickson Page A

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 compassionatecommunities 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, for 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 upwhen 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