In the post on pair-bonding there was a question wabout the varieties of love, bonding, etc. Chapter 4 of Why We Love (see previous post) is devoted to analyzing and decoupling long term attachment, romantic love and lust. Of these three, long term attachment seems most related to "pair-bonding." The author notes, that:

• fMRI images that sketch out brain activity associated with lust (exposure to erotic images) differ a great deal from the those associated with romantic love (in this case, the author performed many fMRIs on couples who were in the first flower of romantic love).
  
• Lust is also correlated with testosterone, explaining why males and older women tend to have a higher libido (as women age, their estrogen level drops, so their relative level of testosterone increases).
  
• Romantic love can feed into lust because dopamine (associated with the former) can induce the release of testosterone (associated with the latter).
  
• The reverse can also happen, in that increased levels of testosterone (associated with lust) can release dopamine (associated with romantic love).
  
• The relationship between lust and long term attachment (correlated with vasopressin and oxytocin in males and females respectively) is complicated, but in general the author offers that there is likely a mild negative relationship as the two "attachment hormones" dampen the release of testosterone and vice versa (though this is not a deterministic rule).
  
• The relationship between romantic love and long term attachment is even more confused (ie; dopamine and its associated chemicals and vasopressin and oxytocin).
  

The narrative above is not totally convincing, and the "chemical soup" model is obviously simplistic (the author seems to acknowledge this in asides, but I don't think many readers will catch them). Additionally, she is using the standard Evolutionary Psychology method of focusing on average or universal tendencies so it is possible that different "strategies" are confounding her perception as substructured trends are being compressed together. There is an admission that both men and women vary in the level of basal testosterone in their systems, which tends to have a strong correlation with various behaviors (lots of testosterone ~ lots of sex),¹ so perhaps the countervailing data points might simply be that chemical pathways settle at different equilibria from individual to individual.

Nevertheless she is able to map the soup-chemical pathway model on to some of the tendencies we see among people in the real world. There are cases where people have an instant attraction which later soldifies into love. Cases where you are friends with someone, and at some point either lust or love get triggered. There is the tendency for lust and romantic love to frade into attachment. More refinement of the models are needed so that description can be translated more clearly into prescription, at which point perhaps our mastery of the chemistry of love will have matured enough that a pill can trigger the appropriate reactions and phase change mental state upon a whim....

1 - Simon Baron-Cohen suggests that high testerone women and low testosterone men are better at math.