I thought this was pretty interesting. [quote]Many other studies have found the same thing: love operates as a motivation and reward system in the brain. So, if love is rewarding, what drives us to cheat on people we fall in love with? The problem is that romantic love isn't the only brain system that is activated when we fall for someone. There are actually three brain systems related to love, Fisher explained. There's the sex drive, which is like an "intolerable neural itch," to get us out searching for a range of partners to help pass on our genes. There's romantic love, which helps us focus our mating energy on one person. And then there's attachment, the calm and security we feel with a long-term partner so we can raise children with them as a team. However, those three brain systems, sex drive, romantic love, and attachment, aren't always connected to each other. So it's possible to feel deep attachment to a long-term partner at the same time you feel intense romantic love toward someone else and even also feel sexual attraction toward another person, Fisher said.[/quote]