I found this interesting nugget in a story from last year reporting on the research of Arthur Aron, Helen Fisher and Lucy Brown. Fisher, author of "Why We Love," and the team scanned the brains of 17 people who said they were intensely in love.
When people looked at photos of their beloveds, it was the reward systems of their brains that were activated -- not the emotional center or lust system. The researchers think this indicates that romantic love is more of a motivational state designed to capture the prize of love, rather than an emotion itself.
This explains why we're so willing to ditch responsibilities and blow off friends and family when we're newly in love.
“Humans have evolved three distinct but interrelated brain systems for mating and reproduction – the sex drive, romantic love, and attachment to a long term partner,” Fisher said, “and our results suggest how feelings of romantic love might change into feelings of attachment. Our results support what people have always assumed – that romantic love is one of the most powerful of all human experiences. It is definitely more powerful than the sex drive.”
Fisher says the study also shows continuity between human romantic love and attraction in other animals.
"Other scientists,” she said, “have reported that expressions of attraction in a female prairie vole are associated with a 50% increase in dopamine activity in a brain region related to regions where we found activity. These and other data indicate that all mammals may feel attraction to specific partners, and that some of the same brain systems are involved.”
The bonding effects of oxytocin have been clearly demonstrated in the cuddly and monogamous prairie vole, leading to intriguing extrapolations to human monogamy. This is another data point showing that these extrapolations may not be so far-fetched.