Chilean poet Pablo Neruda could be considered a literary love expert. In 1960, he penned "100 Love Sonnets," describing in fervid detail the multiple angles and manifestations of that deep, romantic attachment both hailed and hated by countless poets and writers like him. Honing in on the core of humans' most-prized emotion, Neruda sweetly refers to love in Sonnet No. 53 as "this endless simplicity of tenderness" [source: Clarke].
Not surprisingly, science doesn't handle love so gently. In fact, it doesn't even classify love as an emotion, but rather a goal-orientated motivational state that drives humans toward an array of strange behaviors reminiscent of those associated with drug addiction and psychosis [source: Fisher et al]. And at the risk of stripping love entirely of sentiment, science concludes that those crazy, sometimes stupid behaviors boil down to a cocktail of chemicals buzzing around our brains -- not fate or benevolent serendipity, as some believe. On the one hand, those cold, hard facts might kill the mood, while on the other, they offer a kind of comfort: When love overwhelms our actions, attention spans and impulses, we can understand how the following five neurochemical culprits are largely to blame.