A General Theory of Love
by Thomas Lewis, M.D., Fari Amini, M.D., Richard Lannon, M.D.
(Vintage Books) $13

In Our Nature: Stories of Wildness
selected by Donna Seaman
(Dorling Kindersley Publishing Inc.) $22.95

Love is mute and necessary, a scientifically measurable biological need. Two books, A General Theory of Love and In Our Nature: Stories of Wildness, approach the topic of love from different disciplines. The former is written by three psychiatrists, the latter is a collection of short stories by such well-known authors as Francine Prose, Lorrie Moore, and Rick Bass. While the psychiatrists better reveal the science of love, the fiction writers better illustrate it.

A General Theory of Love is a quick read, with one overwhelming theme: To be a functional, content adult, one needs to have been a well-loved, well-cared-for child, with parents who provide a healthy example of a loving relationship. The authors cite numerous studies illustrating that we will not thrive if not cared for, that love is more biologically vital than food: "A mother who had been consistently attentive, responsive and tender to her infant raised a secure child." Mothers who were distant or erratic in their attentions produced insecure, troubled kids.

The first piece in the short-story collection is "Swamp Boy," by Rick Bass. Swamp Boy is regularly beaten up by his classmates, but somehow doesn't seem upset by their attacks. His assailants spy on Swamp Boy's home: "We watched him and his family at the dinner table, watched them say grace, say amen, then eat and talk. It wasn't as if we were homeless or anything--this was back when we all still had both our parents, when almost everyone did--but still, his house was different. The whole house seemed to come alive when the family was inside it, seemed to throb with a kind of strength." The boys sense the love that fortifies Swamp Boy; the fact that his parents care for him is clear from outside.

What makes love communicable is limbic resonance, a sort of physical mind-reading. The brain has three components: reptilian, limbic, and neocortal. This triune brain is a piling on of evolutionary developments, from the most primitive (reptilian), which is barely more than involuntary instinct, to the limbic brain, the evolutionary advancement allowing mammals to care for their young. It is the seat of emotionality. The neocortex is the human addition: the location of language centers and higher thought. Love is largely subconscious, operating from the limbic brain through limbic resonance, which is defined as "a symphony of mutual exchange and internal adaptation whereby two mammals become attuned to each other's inner states." It's what makes watching an action film in a packed theater so much more exciting than seeing it with only a few other people, it's how panic works a crowd, how your cats know you're in a bad mood as soon as you open the door.

In Francine Prose's story "Everything Is about Animals," a woman's lover returns from relocating a population of monkeys. He has been caring for monkeys for two months, and is turning monkey. She can't quite reach him, and frets: "Once, long ago, a lover left her for someone else, a friend... the worst thing was wondering if the best way to win him back was to be more or less like that friend. What she feels now is so similar; she thinks: Should I be more human or more monkey?" His limbic resonance has crossed species lines, and can't seem to make it home to human. Through Prose's beautiful, lucid writing, this scenario is not so farfetched as maybe it ought to be.

The most compelling idea put forth in A General Theory of Love is the idea of open-loop limbic resonance, the idea that our brain functions are created and physically changed by those we care for. "Because loving is a reciprocal physiologic influence, it entails a deeper and more literal connection than most realize. Limbic regulation affords lovers the ability to modulate each other's emotions, neurophysiology, hormone status, immune function, sleep, rhythms, and stability.... Lovers hold the key to each other's identities, and they write neostructural alterations into each other's networks." When your lover is away, you might not sleep, not simply because you miss him, but because your brain misses the regulation his brain offers, a sort of primitive, mutually dependent loop. This explains why cancer patients with strong support systems fare better than those without, why pets help lower their owner's blood pressure, and why many people have trouble finding contentment alone. It's hard-wired, this drive to couple.

A General Theory of Love offers numerous studies concerning childhood development, but lacks such overwhelming evidence proving love's specific effects on adult relationships; sex is untouched. What I want to know is how to live the present of my life, not as a parent or child, but as a lover, for this seems to be the vital role we occupy within the authors' theory. There is no hard science to answer this question. The stories of In Our Nature seem better equipped to make clear illustrations of how we love, and why, and that sometimes, there is no communication between the two.