Julia Stuart in The Independent:
Love can be divided into three entities: lust, romance and attachment, according to anthropologist Dr Helen Fisher, who has been studying the subject for 32 years. These three brain systems can operate in any order and in any combination. You can fall in love with someone before you sleep with them; you can become deeply attached to somebody and then fall in love with them; and you can have a sexual relationship, fall in love and then become deeply attached.
Lust is a craving for sexual gratification, which you can feel for a whole range of people. Those caught up in romantic love focus all their attention on the object of their affection. Not only do they crave them, but they are highly motivated to win them, they obsessively think about them and become extremely sexually possessive. Perhaps illogically, if things go wrong. they are attracted to them even more. During this state the brain is driven by dopamine, a neurotransmitter central to the reward system.
Romantic love is much more powerful than sex drive, says Dr Fisher, of Rutgers University, New Jersey. And she believes it to be a drive, rather than an emotion. “It doesn’t have any facial expression, it’s very difficult to control and it’s one of the most powerful neural systems that has evolved,” she says.
The third brain system is attachment – that sense of calm and security you can feel for a long-term partner. It is associated with the hormones vasopressin and oxytocin, which are probably responsible for the sense of peacefulness and unity felt after having sex. Holding hands also drives up oxytocin levels, as does looking deeply into your loved one’s eyes, massage, and simply sitting next to them.