“According to scientists, there are three stages of love: lust, attraction, and attachment. And, it turns out, each of the stages is orchestrated by chemicals—neurotransmitters—in the brain.

As you might expect, lust is ruled by testosterone and estrogen.

The second stage, attraction, is governed by dopamine and serotonin. When, for example, couples report feeling indescribably happy in each other’s presence, that’s dopamine, the pleasure hormone, doing its work.

Taking cocaine fosters the same level of euphoria. In fact, scientists who study both the brains of new lovers and cocaine addicts are hard-pressed to tell the difference.

The second chemical of the attraction phase is serotonin. When couples confess that they can’t stop thinking about each other, it’s because their serotonin level has dropped. People in love have the same low serotonin levels as people with OCD. The reason they can’t stop thinking about each other is that they are literally obsessed.

Oxytocin and vasopressin control the third stage: attachment or long-term bonding. Oxytocin is released during orgasm and makes you feel closer to the person you’ve had sex with. It’s also released during childbirth and helps bond mother to child. Vasopressin is released postcoitally.

Natasha knows these facts cold. Knowing them helped her get over Rob’s betrayal. So she knows: love is just chemicals and coincidence.

So why does Daniel feel like something more?”