“I love you.” It’s a simple statement, only three words, yet it packs an incredible amount of science. Yes, you read that right, science. Love is more than the emotional outpourings of your heart (which is an organ folks; that’s the study of anatomy and physiology, which is science). Love is the chemical activity taking place in your brain.

Dr. Helen Fisher, biological anthropologist at Rutgers University, and her team defined three stages of love: lust, romantic attraction, and attachment. Dr. Fisher calls these the three core brain systems for mating and reproduction. Her team made MRI scans on 49 people to study the circuitry of love. Seventeen people were newly in love, 15 had just been dumped, and 17 were still in love after an average of 21 years of marriage. Subjects looked at a photo of their sweetheart for one scan and a neutral photo for a second scan. Dr. Fisher’s team found a remarkable amount of brain activity when looking at these images, mainly at the ventral tegmental area (VTA). The VTA, located at the base of the brain, is basically the brain’s reward system. It is considered part of the reptilian core of the brain that is associated with wanting, craving, motivation, and focus. It is more powerful than the sex drive and it is the region of the brain which is active during a cocaine high. Love is like a drug. Literally.

Dr. Fisher researched how different hormones drive each stage. Here, I present to you, the science of love in 3 acts.

ACT 1: Lust (or, Sex Drive)
Lust is the stage that Dr. Fisher says, “evolved primarily to motivate individuals to seek sexual unions with any” individual. You came to the party already willing to dance with no particular person in mind. Lust is driven by the sex hormones testosterone and estrogen, both found in mammals and other vertebrate animals. Testosterone is the principal male sex hormone. Estrogen is the principal female sex hormone. And, if you meet someone you find attractive, with the power of lust hormones, you may just initiate stage two.

ACT 2: Romantic Attraction
When you find yourself crazy in love, unable to eat or sleep, and daydreaming obsessively about your lover, you are in romantic attraction. Fueling your attraction is dopamine, a neurotransmitter that feeds the brain’s reward and pleasure centers. It’s that euphoric feeling.

Dopamine is accompanied by adrenaline, which activates the stress response and sets your heart to race, and serotonin, which your brain maintains at a low level during the rush of love. This low-level is similar to the patterns of people with obsessive compulsive disorder.

ACT 3: Attachment
Finally, you and your love have survived a good 6 months together and no longer get butterflies every time you see each other; you are attached and committed to each other. This stage is driven by oxytocin, an incredibly powerful hormone released during orgasm that makes couples feel close. Oxytocin is actually a long-lasting chemical that can continue to flow in your brain; unlike continuous dopamine surges, which would be more distressing than rewarding after a while. Oxytocin does not give the same highs as dopamine, rather it creates a feeling of contentment. This is true companionship.

A beautiful three-act play converges to form love; but, what about the downside of these chemical responses and love? Well, for one, the effects on your brain when you get dumped occur in the same place as attraction happens. How frustrating for the poor dumped soul and no wonder it takes so long to get over someone we love.

Another drawback is casual sex may not go as casual as planned. You can fall in love with someone you’re having just casual sex with. There is a spike in dopamine (romantic attraction) during orgasm and then a rush of oxytocin (attachment), and this can fool you into thinking you have just had a cosmic union with someone instead of casual sex.

And, lastly (in my blog, I’m sure others can find more), Dr. Fisher noted that antidepressants (SSRIs) raise the level of serotonin and this suppresses the dopamine circuit, which is related to romantic love. SSRIs are also known for killing the sex drives, which kills orgasm, which kills oxytocin.

On a good note, Dr. Fisher said, “millions of years ago we evolved 3 basic drives: sex drive, romantic love, and attachment to a long-term partner. These circuits are deeply embedded in the human brain. They are going to survive as long as our species survives.”

So, go forth and love this Valentine’s Day, but do so with respect to science.