In his latest book The Moral Molecule, neuroeconomist Paul Zakdescribes oxytocin’s role in trust, bonding and even virtuous behaviour. New Scientist caught up with him about avoiding the term “the cuddle chemical” and trying not to make a bride faint on her wedding day.
Why study moral behaviour?
Before my mother was my mother she was a nun, so morality was something that was very present. We had very clear top-down guidance: “you do this and you go to heaven, you do that and you go to hell”. Even as a child I felt that that was incredibly harsh and wrong. The idea that there’s some perfect received wisdom to tell the difference between right and wrong just didn’t make any sense to me. I wanted to find a concrete, biological basis for good and bad behaviour in humans.
Before my mother was my mother she was a nun, so morality was something that was very present. We had very clear top-down guidance: “you do this and you go to heaven, you do that and you go to hell”. Even as a child I felt that that was incredibly harsh and wrong. The idea that there’s some perfect received wisdom to tell the difference between right and wrong just didn’t make any sense to me. I wanted to find a concrete, biological basis for good and bad behaviour in humans.
It’s not my place to say whether God exists or not, but it seemed like there were all kinds of good people who weren’t raised Catholic like I was. And that seemed like a deep mystery about life: if there are 2000 religions, why do we see a large number of those having the same kind of prescriptions for what constitutes good behaviour and a good life? That was the deeper, personal reason that, in retrospect, drove ten years of hard labour in the lab and in the field.
What got you interested in oxytocin?
I had done work in the late 1990s showing that countries in which levels of interpersonal trustwere high were richer countries, and countries that were poor were by and large low trust countries.
I had done work in the late 1990s showing that countries in which levels of interpersonal trustwere high were richer countries, and countries that were poor were by and large low trust countries.
Having done that, the next logical question was: for a given country, why would you ever trust a stranger? Across biology, psychology, economics, and neuroscience, no one really had an answer.
When I started searching the literature for possible mechanisms for why we might want to trust strangers, I came across animal research on oxytocin that suggested the molecule allowed group-living animals to tolerate their burrow mates. I thought tolerating others and trusting others may lie on a continuum. So I found this target in the brain that had been largely ignored. There’s no medical condition associated with too much or too little oxytocin, other than preterm labour. At the time, oxytocin was thought just to be a drug used in labour, and no one really studied it. It was just sort of sitting on the shelf.
How is oxytocin involved in human trust?
In our research, we were able to show that when we’re trusting other people, our brains release oxytocin. Moreover, when we manipulate oxytocin pharmacologically we can induce people to trust others really readily, without affecting their cognition or memory.
In our research, we were able to show that when we’re trusting other people, our brains release oxytocin. Moreover, when we manipulate oxytocin pharmacologically we can induce people to trust others really readily, without affecting their cognition or memory.
How do you get from trust to morality?
I thought: “Gee, trust is kind of a social glue that keeps society together. The other kind of social glue is good behaviours that people engage in, even when no one’s watching, such as giving to charity. If oxytocin makes people trusting, would it make them generous? Would it make them kind? Would it make them caring?” And so we began knocking out all the virtuous behaviours we could think of in the laboratory and in the field and just seeing if oxytocin was associated with them. And by and large we found that the vast majority of virtuous behaviours and moral behaviours were linked to oxytocin blood levels.
I thought: “Gee, trust is kind of a social glue that keeps society together. The other kind of social glue is good behaviours that people engage in, even when no one’s watching, such as giving to charity. If oxytocin makes people trusting, would it make them generous? Would it make them kind? Would it make them caring?” And so we began knocking out all the virtuous behaviours we could think of in the laboratory and in the field and just seeing if oxytocin was associated with them. And by and large we found that the vast majority of virtuous behaviours and moral behaviours were linked to oxytocin blood levels.
So oxytocin makes us more moral?
I would say oxytocin makes us care about others around us, including complete strangers. In many, many experiments, when we raise oxytocin through a stimulus or pharmacologically, people in tangible ways tend to care more about others who they don’t know, people they can’t see and people all around the world. For example, they’ll give more to charity; they’ll do a painful task to help somebody. That’s actually pretty amazing - that a lot of this good behaviour that we see in the world is driven by this ancient molecule that modulates approach and withdraw behaviour in animals. It not only makes us care about strangers, but it makes us feel good to do good.
I would say oxytocin makes us care about others around us, including complete strangers. In many, many experiments, when we raise oxytocin through a stimulus or pharmacologically, people in tangible ways tend to care more about others who they don’t know, people they can’t see and people all around the world. For example, they’ll give more to charity; they’ll do a painful task to help somebody. That’s actually pretty amazing - that a lot of this good behaviour that we see in the world is driven by this ancient molecule that modulates approach and withdraw behaviour in animals. It not only makes us care about strangers, but it makes us feel good to do good.
Can human morality really be explained by a single molecule?
The short answer is no. What we’ve found in our ten years of experimenting is that an evolutionarily ancient molecule is responsible for a large number of prosocial behaviours, which we’d generally call moral or virtuous because they involve putting someone else’s needs in front of your own. Most social creatures tend to avoid or ostracise individuals who are not co-operators.
The short answer is no. What we’ve found in our ten years of experimenting is that an evolutionarily ancient molecule is responsible for a large number of prosocial behaviours, which we’d generally call moral or virtuous because they involve putting someone else’s needs in front of your own. Most social creatures tend to avoid or ostracise individuals who are not co-operators.
Human oxytocin-mediated empathy involves, besides oxytocin, both serotonin and dopamine, which reinforce moral behaviours. This leads people to perform moral actions even when they don’t have to. In times of high stress, adrenaline inhibits the release of oxytocin. This also happens when testosterone levels are high. There are a variety of ways, we’ve found, that we can turn off or turn on this moral behaviour. Sometimes it’s not appropriate. If you’re a soldier in battle and someone’s trying to kill you, it’s appropriate to try to save your life and the lives of others around you. This system is adaptive. It’s not as simple as “oxytocin makes us moral” - oxytocin is part of a system of chemicals that our brain lives in that takes information from your environment and turns that into a predilection towards action.
Do you think oxytocin deserves its reputation as the cuddle chemical?
Sure, yes. We’ve shown that even being touched by a stranger will induce oxytocin release. I avoided the “cuddle chemical” and “love hormone” monikers for the longest time because they’re not really scientific, but evolutionarily it’s important in mammals for maternal and paternal care for offspring. So there is the case to be made for oxytocin as a love chemical. It’s also released by both sexes during sex, and so it does work to snuggle up and stay together.
Sure, yes. We’ve shown that even being touched by a stranger will induce oxytocin release. I avoided the “cuddle chemical” and “love hormone” monikers for the longest time because they’re not really scientific, but evolutionarily it’s important in mammals for maternal and paternal care for offspring. So there is the case to be made for oxytocin as a love chemical. It’s also released by both sexes during sex, and so it does work to snuggle up and stay together.
What about the theory that oxytocin has a “dark side”, and is involved in racism and envy?
If you look at those papers, they are very poorly done. There is actually very little evidence that oxytocin motivates group hate or envy. The experiments were very poorly designed and the data did just not support those conclusions. It’s easy to get in group biases, but oxytocin does not seem to make us hate others that are not part of our group. It’s part of a large brain circuit that’s trying to help us modulate the right type of behaviour. In soldiers and rugby players we see a lot of in-group bonding and a lot of out-group aggression. During a warm up there is an increase in oxytocin associated with in group bonding, but not with out-group aggression. The out-group aggression is only indirectly associated with oxytocin - you’re more effective if there’s bonding within the group.
If you look at those papers, they are very poorly done. There is actually very little evidence that oxytocin motivates group hate or envy. The experiments were very poorly designed and the data did just not support those conclusions. It’s easy to get in group biases, but oxytocin does not seem to make us hate others that are not part of our group. It’s part of a large brain circuit that’s trying to help us modulate the right type of behaviour. In soldiers and rugby players we see a lot of in-group bonding and a lot of out-group aggression. During a warm up there is an increase in oxytocin associated with in group bonding, but not with out-group aggression. The out-group aggression is only indirectly associated with oxytocin - you’re more effective if there’s bonding within the group.
In the book, you describe some pretty unusual experiments - including one involving one of our reporters. Tell me about what you call “the vampire wedding”
It’s such a lovely story. New Scientist reporter Linda Geddes had been following my research for a number of years. Before her wedding, she called me to ask if I’d thought of looking at oxytocin release at weddings, and if I’d be interested in investigating at her ceremony. I said “Sure!”
It’s such a lovely story. New Scientist reporter Linda Geddes had been following my research for a number of years. Before her wedding, she called me to ask if I’d thought of looking at oxytocin release at weddings, and if I’d be interested in investigating at her ceremony. I said “Sure!”
So we got it all arranged, we got there, and then right before we took her first blood sample, when I asked her if she was OK, she said “actually, I have a fear of needles”, so I said: “Oh no”. My fear was that I’d make the bride faint on her wedding day, and the whole thing would be ruined. I really didn’t want to spoil her wedding, but she was a great sport. It’s one of the few experiments I’ve gone to with smelling salts - just in case somebody fainted, I wanted to be ready to revive them quite quickly.
But it was fabulous. It looks as though humans have devised this ritual that induces oxytocin release in a way that bonds people to the wedding party. It provides this social support system, so that this couple presumably can be successful at reproducing. And not only do I know that from the data but I know that from my personal experience. I still feel very close to Linda and [her husband] Nic. I shared an amazing experience with them.
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