Why him? why her?

the long version

Helen Fisher, one of the world's leading experts on romantic love, unlocks the hidden code of desire and attachment. Each of us, it turns out, primarily expresses one of four broad personality types--Explorer, Builder, Director, or Negotiator--and each of these types is governed by different chemical systems in the brain. Driven by this biology, we are attracted to partners who both mirror and complement our own personality type. Drawing on her unique study of 40,000 men and women, Fisher explores each personality type in detail, shows you how to identify your own type, and explains why some types match up well, whereas others are problematic.--From publisher description.