Three minutes into the date, these two might have already made up their minds about each other.

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Falling in Love in Three Minutes or Less

Helen Fisher, a prominent anthropologist known for her research on attraction and love, believes three minutes is all you need to know whether someone will be in your life for a while [source: Fisher]. To understand her theory, we have to travel back in time to the days of early humans. Our ancestors lived shorter lives than we do, and it was important in their brief time on Earth to mate and produce a healthy child so that the race would live on. For this reason, they had to size up potential mates quickly, just as they had to quickly size up whether a stranger was friend or foe. Fisher believes our evolutionary past wired our brains so that we know pretty quickly whether we might want to mate with someone (even if we're not even looking to have a child).

So what are we considering in those three minutes? Many scholars speak of the concept of a "lovemap," a laundry list of traits that we want in a partner, which means that when you told a girlfriend that your next boyfriend needed to be tall and have a sense of humor, you were actually working on a lovemap. But while you may have some ideas about what you find attractive in a potential paramour, these ideals of beauty were likely influenced by those evolutionary ancestors again.

Men and women both wanted to ensure that their children would live and pass on their genes, so they needed to be sure that the other party was bringing the best genetic makeup to the table. We often signal our physical and reproductive health with traits like a certain waist-to-hip ratio or a symmetrical face; scientists have found that these qualities are universally attractive to others. And when you check out a guy's chin or a lady's lovely eyes, you're actually looking at traits that are shaped by the amounts of testosterone and estrogen in their bodies, respectively, which also indicate reproductive fitness. So when we comment on someone's hotness, we're actually commenting on ancient ideals of fertility.

So we can tell pretty quickly whether someone will give us a cute, healthy baby. But is that love, or just lust? Fisher points out that the sections of the brain that respond to love and lust are different, though they can light up at the same time. In a study conducted at Syracuse University, researchers found that the hormones associated with love, rather than lust, can flood the brain in one-fifth of a second [source: Syracuse University]. It seems to indicate that our brain can start feeling amorous pretty quickly, but on the next page, we'll consider more elements of the lovemap and what else might be going on in that 0.2-second to three-minute time span.