We kick-started the year with some of history’s most beautiful definitions of love. But timeless as their words might be, the poets and the philosophers have a way of escaping into the comfortable detachment of the abstract and the metaphysical, leaving open the question of what love really is on an unglamorously physical, bodily, neurobiological level — and how that might shape our experience of those lofty abstractions. That’s precisely what psychologist Barbara Fredrickson, who has been studying positive emotions for decades, explores in the unfortunately titled but otherwise excellent Love 2.0: How Our Supreme Emotion Affects Everything We Feel, Think, Do, and Become (UK; public library). Using both data from her own lab and ample citations of other studies, Fredrickson dissects the mechanisms of love to reveal both its mythologies and its practical mechanics.

She begins with a definition that parallels Dorion Sagan’s scientific meditation on sex:

First and foremost, love is an emotion, a momentary state that arises to infuse your mind and body alike. Love, like all emotions, surfaces like a distinct and fast-moving weather pattern, a subtle and ever-shifting force. As for all positive emotions, the inner feeling love brings you is inherently and exquisitely pleasant — it feels extraordinarily good, the way a long, cool drink of water feels when you’re parched on a hot day. Yet far beyond feeling good, a micro-moment of love, like other positive emotions, literally changes your mind. It expands your awareness of your surroundings, even your sense of self. The boundaries between you and not-you — what lies beyond your skin — relax and become more permeable. While infused with love you see fewer distinctions between you and others. Indeed, your ability to see others — really see them, wholeheartedly — springs open. Love can even give you a palpable sense of oneness and connection, a transcendence that makes you feel part of something far larger than yourself. […] Perhaps counterintuitively, love is far more ubiquitous than you ever thought possible for the simple fact that love is connection. It’s that poignant stretching of your heart that you feel when you gaze into a newborn’s eyes for the first time or share a farewell hug with a dear friend. It’s even the fondness and sense of shared purpose you might unexpectedly feel with a group of strangers who’ve come together to marvel at a hatching of sea turtles or cheer at a football game. The new take on love that I want to share with you is this: Love blossoms virtually anytime two or more people — even strangers — connect over a shared positive emotion, be it mild or strong.

Fredrickson zooms in on three key neurobiological players in the game of love — your brain, your levels of the hormone oxytocin, and your vagus nerve, which connects your brain to the rest of your body — and examines their interplay as the core mechanism of love, summing up:

Love is a momentary upwelling of three tightly interwoven events: first, a sharing of one or more positive emotions between you and another; second, a synchrony between your and the other person’s biochemistry and behaviors; and third, a reflected motive to invest in each other’s well-being that brings mutual care.

She shorthands this trio “positivity resonance” — a concept similar to limbic revision — and likens the process to a mirror in which you and your partner’s emotions come into sync, reflecting and reinforcing one another:

This is no ordinary moment. Within this mirrored reflection and extension of your own state, you see far more. A powerful back-and-forth union of energy springs up between the two of you, like an electric charge.

What makes “positivity resonance” so compelling a concept and so arguably richer than traditional formulations of “love” is precisely this back-and-forthness and the inclusiveness implicit to it. Fredrickson cautions against our solipsistic view of love, common in the individualistic cultures of the West:

Odds are, if you were raised in a Western culture, you think of emotions as largely private events. you locate them within a person’s boundaries, confined within their mind and skin. When conversing about emotions, your use of singular possessive adjectives betrays this point of view. You refer to ‘my anxiety,’ ‘his anger,’ or ‘her interest.’ Following this logic, love would seem to belong to the person who feels it. Defining love as positivity resonance challenges this view. Love unfolds and reverberates between and among people — within interpersonal transactions — and thereby belong to all parties involved, and to the metaphorical connective tissue that binds them together, albeit temporarily. … More than any other positive emotion, then, love belongs not to one person, but to pairs or groups of people. It resides within connections.

Citing various research, Fredrickson puts science behind what Anaïs Nin poetically and intuitively cautioned against more than half a century ago:

People who suffer from anxiety, depression, or even loneliness or low self-esteem perceive threats far more often than circumstances warrant. Sadly, this overalert state thwarts both positivity and positivity resonance. Feeling unsafe, then, is the first obstacle to love.

But perhaps the insight hardest to digest in the age of artificial semi-connectedness — something Nin also cautioned against a prescient few decades before the internet — has to do with the necessary physicality of love:

Love’s second precondition is connection, true sensory and temporal connection with another living being. You no doubt try to ‘stay connected’ when physical distance keeps you and your loved ones apart. You use the phone, e-mail, and increasingly texts or Facebook, and it’s important to do so. Yet your body, sculpted by the forces of natural selection over millennia, was not designed for the abstractions of long-distance love, the XOXs and LOLs. Your body hungers for more. […] True connection is one of love’s bedrock prerequisites, a prime reason that love is not unconditional, but instead requires a particular stance. Neither abstract nor mediated, true connection is physical and unfolds in real time. It requires sensory and temporal copresence of bodies .The main mode of sensory connection, scientists contend, is eye contact. Other forms of real-time sensory contact — through touch, voice, or mirrored body postures and gestures — no doubt connect people as well and at times can substitute for eye contact. Nevertheless, eye contact may well be the most potent trigger for connection and oneness. […] Physical presence is key to love, to positivity resonance.

While Fredrickson argues for positivity resonance as a phenomenon that can blossom between any set of people, not just lovers, she takes care to emphasize the essential factor that separates intimate love from other love: time.

Love is a many-splendored thing. This classic saying is apt, not only because love can emerge from the shoots of any other positive emotion you experience, be it amusement, serenity, or gratitude, but also because of your many viable collaborators in love, ranging from our sister to your soul mate, your newborn to your neighbor, even someone you’ve never met before. […] At the level of positivity resonance, micro-moments of love are virtually identical regardless of whether they bloom between you and a stranger or you and a soul mate; between you and an infant or you and your lifelong best friend. The clearest difference between the love you feel with intimates and the love you feel with anyone with whom you share a connection is its sheer frequency. Spending more total moments together increases your chances to feast on micro-moments of positivity resonance. These micro-moments change you. […] Whereas the biological synchrony that emerges between connected brains and bodies may be comparable no matter who the other person may be, the triggers for your micro-moments of love can be wholly different with intimates. The hallmark feature of intimacy is mutual responsiveness, that reassuring sense that you and your soul mate — or you and your best friend — really ‘get’ each other. This means that you come to your interactions with a well-developed understanding of each other’s inner workings, and you use that privileged knowledge thoughtfully, for each other’s benefit. Intimacy is that safe and comforting feeling you get when you can bask in the knowledge that this other person truly understands and appreciates you. You can relax in this person’s presence and let your guard down. Your mutual sense of trust, perhaps reinforced by your commitments of loyalty to each other, allows each of you to be more open with each other than either of you would be elsewhere.

(As the silent half of Penn & Teller once poignantly remarked, “Sometimes magic is just someone spending more time on something than anyone else might reasonably expect.”)

Complement Love 2.0, a fine addition to these essential books on the psychology of love, with the indispensable A General Theory of Love.