How do we make romantic decisions? Should we go with our gut, or use the empirical model, approaching love with the comforting certainty of a pro-and-con list? Advances in neuroscience are revealing how the brain makes such choices – including the choice of who we decide to settle down with for life, and how we decide when to do that.

“We know from how the brain works that there is so much information that cannot be accounted for in a spreadsheet,” says Jonah Lehrer, whose new book, How We Decide, presents the latest research on the process of decision-making.

In other words, our rational sides are simply not equipped to make complex and far-reaching decisions like when to get married. “The rational brain can only take in seven pieces of information at one time,” Lehrer says. “When it gets more than that, it’s like an old computer trying to run Vista.”

“The rational brain can only take in seven pieces of information at one time,” Lehrer says. “When it gets more than that, it’s like an old computer trying to run Vista.”

Because of this limitation – and because love brings with it such a bombardment of considerations – Lehrer is a proponent of listening to the emotional part of our brains when making such decisions, which can process more information than the analytical part.

This part of the brain is called the orbitofrontal cortex (OFC). When we are drawn to a person (or a type of music, or an ice cream flavor), that’s the OFC flexing its mental muscle. It’s the part of the brain that integrates visceral emotions into the decision-making process, and reacts to feelings of reward.

The OFC can be remarkably adept at picking up on unconscious emotional cues – it’s where the emotion is manifested from the unconscious to the conscious. Lehrer had one of these moments when he met his wife -- he got so flustered that he gave her the wrong phone number. “I was impressed by how useless and flabbergasted I was because I always thought of myself as empirical and rational,” he says. After his foray into the labs of many of the world’s leading neuroscientists, Lehrer believes this experience was his OFC absorbing some crucial piece of information he wasn’t consciously aware of.

But what is the margin of error for the OFC? Should it be trusted for solving conundrums of love and long-term compatibility? Not entirely. Your emotional brain, like your rational brain, is not always correct and can be misled by factors both personal and external.

Charles Darwin, the quintessential rationalist, tried to use only logic to make such decisions. When he wrote “This is the Question,” a set of notes he drafted between 1837 and 1838, he was not pondering finches. “This is the Question” represented the evolutionary theorist’s attempt to logically evaluate whether he should marry his girlfriend, Emma Wedgwood.

Using his trademark rationality, Darwin made two columns: “Marry” and “Not Marry.”

In the ”Marry” column, he entered things like: “Home and someone to take care of house—Charms of music and female chit-chat. These things good for one’s health.” In the “Not Marry” column was: “Freedom to go where one liked—Choice of Society and little of it. Conversations of clever men at clubs. Not forced to visit relatives, and to bend to every little trifle.”

The Origin of Species author used this dispassionate calculation to ultimately reach a conclusion. On January 29, 1839, Miss Emma Wedgwood became Mrs. Emma Darwin.

Darwin’s struggle to make such a decision intelligently is hardly a dusty vestige of another era. But, “the kind of list that Darwin made was completely useless,” says Lehrer.

Lehrer argues that while unconscious emotional instincts can have merit, he doesn’t believe they should be acted upon immediately. In fact, he waited years before proposing to his wife. Nor is he a confederate of the Blink school of thought, popularized by Malcolm Gladwell, which promotes the value of rapid decision-making, or “thinking without thinking.”

Part of why “thinking without thinking” is dangerous when it comes to romantic decision-making is because there are potent brain chemicals at work that can overwhelm you, the most intoxicating of which is dopamine, a neurotransmitter brain cells use to communicate with each another. Dopamine does a number on our heartstrings—it’s a feel-good chemical. David Goldman, a neuroscientist with the National Institute of Alcohol Abuse and Alcoholism, aptly described dopamine in a Psychology Today article as a chemical that “brightens and highlights our connection with the world around us,” which makes it fun but also a little like being drunk. And because it can produce the “infatuation” sensation smitten lovers experience, being on a dopamine drip is not the ideal time to make a decision about the long-term potential of a relationship. The potency—and danger—of dopamine is that it can obfuscate meaning and make us see significant trends where none exist.

The more reliable brain chemical for romantic decision-making is oxytocin, which increases trust and is part of the circuitry of attachment. Women get a surge of it when they give birth. A study found that humans who are administered oxytocin looked toward the eyes of people in photographs more often and for longer than subjects given a placebo. It’s the chemical of devotion.

If dopamine is the compound that breeds butterflies in our stomachs and causes people to impulsively leave their spouses, oxytocin elicits a feeling of intense compatibility, the kind that makes you think, “I could sit next to this person for the next thirty years.” In matters of the heart, oxytocin provides more clarity in decision-making because it allows you to see your crush with more depth, and with an eye toward the future rather than just the current, fleeting moment.

With practice, could we learn to utilize this knowledge of our own brains to be certain – or at least close to certain – about who and when we choose to marry?

Dr. Robert Burton, a neurologist at the University of California, San Francisco, and the author of On Being Certain: Believing You are Right Even When You’re Not, says certainty is an illusion that arises out of involuntary brain mechanisms that, like love or anger, function independent of reason.

Romantic decisions, like any decisions, says Burton, are based on a wide variety of factors, including sexual attraction and financial security—preferences that are rooted in a subjective iconography and idiosyncrasies, and which amount to little more than a random pastiche of past experiences and pattern recognition. In other words, it’s not that you can never find The One, it’s just that you can’t be sure it’s them, even if you find them. Burton’s advice is, “Start acclimating to uncertainty as a way of life.”

For instance, hours after they had done the math and tied the knot, Burton and his wife were driving to their honeymoon destination when he turned to her and said, “What have I done?” Reflecting on that moment, Burton believes it’s a universal reaction. “I think that’s what every person says after they get married.” Dr. and Mrs. Burton just celebrated their fortieth wedding anniversary.

If you buy into Burton’s model that your thoughts originate out of both prior experience and biology, romantic decision-making takes on a much different hue. “You start to live in a place where you evaluate your thoughts more carefully because we know the brain creates feelings and ideas that aren’t really logical and are based upon personality and biology.”

This is what Lehrer calls meta-cognition—the process of thinking about thinking—and it’s his touchstone for decision-making. “Since the brain is a category buster—it doesn’t think in either/or terms—and could have a black belt in rationalizing, it needs this extra step of cognition to know what parts to silence and what parts to listen to.”

Meta-cognition is also a response to the reality that it’s hard work to understand your emotions. Is it love you are feeling? Or do you just want to stave off loneliness? The brain can get distorted, a point vividly illustrated in a study where a group of undergraduate males were asked to walk across a long, narrow suspension bridge made of wooden boards and wire cables in North Vancouver. A young woman approached the men and asked if he would mind completing a survey, and after he did so the woman gave the men her number and offered to explain the survey in detail if he called. The hitch was that she approached some of the men as they were crossing and some after they had made it to the other side of the treacherous bridge. The men she approached as they were crossing were much likely to call her in the coming days. Why? “The scientists attributed it to the misidentification of those bodily symptoms of fear,” says Lehrer. “They thought they were aroused and attracted, but they were only scared.”

Hannah Seligson is a journalist and the author of New Girl on the Job: Advice from the Trenches. Her second book, A Little Bit Married , will be published by De Capo this spring. Her website is www.hannahseligson.com