（This was from Flamenco_Girl's "Love and Long-Term Relationship (ZT)".  真是懒人会偷懒，哈哈 :^)  ）

"Scientists are discovering that the cocktail of brain chemicals that sparks romance is totally different from the blend that fosters long-term attachment.

Love and obsessive-compulsive disorder could have a similar chemical profile. Studies around the world confirm that passion usually ends. Romantic love is with intense neural activity of infatuation that is in dopamine-drenched state; while comfortable long-term relationship happens in couple with high levels of Oxytocin. The ones lacking of Oxytocin don't form monogamous bonds and tend to roam.

Source: National Geographic Magazine"