An Amazon review on Paul Zak's book states: '"This book is about the hormone oxytocin (which is principally a female hormone but also present in the male). This hormone is the molecule referred to in the title of the book. "Am I actually saying that a single molecule...accounts for why some people give freely of themselves and others are coldhearted bastards, why some people cheat and steal and others you can trust with your life, why some husbands are more faithful than others, and, by the way, why some women tend to be more generous - and nicer - than men?" asks the author Paul Zak. "In a word, yes" he answers.
This molecule as Zak calls it, is a "feel good" hormone that increases when we do simple, feel good things like giving or receiving a hug, or when we give generously. The act of giving stimulates this hormone resulting in the recipient desiring to trust the giver. Zak explains that there is also a counter hormone ("testosterone") which he calls the "bad boy" hormone that increases the impulse to take risk and behave badly. However, testosterone is necessary for physical courage and strength. Thus, the mammalian animal evolved with these two hormones balancing each other and so many of the unusual behavior Zak says, can be attributed to an imbalance of those hormones." Following on from my previous post The Science of Love and Relationships, where John Gottman identifies trust and commitment as being important factors in successful relationships, this talk and Paul Zak's book The Moral Molecule delve into the hormones which affect trust and commitment, namely, oxytocin and testosterone. In the video he makes a fascinating detour referencing a couple of tribes in the Honduras, where certain members actually change sex at puberty (for very demonstrable scientific reasons). Oxytocin is more prevalent in women and testosterone in men, but we all have some of both hormones. According to his talk, men and women react differently when feeling cheated in laboratory experiments. Men desire to take revenge, whereas women get annoyed but are more philosophical about it. However, I can think of plenty of examples where it doesn't play out quite like this in the real world. (Please note: Any personal experiments which involve making women angry are conducted at your own risk; I take no responsibility whatsoever). Oxytocin, as is well known, is released through hugging, eye gazing, and is the hormone which brings on labour in pregnant women as well. So there is a fascinating interplay with testosterone, as detailed above. A woman seeking a male partner will in principle find many of the attributes which come with high testosterone more attractive (for example assertiveness, confidence and courage—which is the willingness to take risks despite potential danger). Yet along with that comes a greater likelihood of a partner being unfaithful and taking unhealthy risks. Lower testosterone in a partner will probably lead to greater stability and harmony, but probably lower status and less excitement as well. I don't know anything about how this plays out in same-sex relationships, which is why I haven't addressed it here.