Oliver Burkeman at The Guardian talks to Paul Zak, an expert on oxytocin, aka 'the moral molecule':
…What drives Zak's hunger for human blood is his interest in the hormone oxytocin, about which he has become one of the world's most prominent experts. Long known as a female reproductive hormone – it plays a central role in childbirth and breastfeeding – oxytocin emerges from Zak's research as something much more all-embracing: the “moral molecule” behind all human virtue, trust, affection and love, “a social glue”, as he puts it, “that keeps society together”. The subtitle of his book, “the new science of what makes us good or evil”, gives a sense of the scale of his ambition, which involves nothing less than explaining whole swaths of philosophical and religious questions by reference to a single chemical in the bloodstream. Being treated decently, it turns out, causes people's oxytocin levels to go up, which in turn prompts them to behave more decently, while experimental subjects given an artificial oxytocin boost – by means of an inhaler – behave more generously and trustingly. And it's not solely because of its effects on humans that oxytocin is known as “the cuddle hormone”: for example, male meadow voles, normally roguishly promiscuous in their interactions with female meadow voles, become passionately monogamous when their oxytocin levels are raised in the lab.
Read more here.