Oxytocin is often called the love hormone. When we cuddle or kiss a loved one, its levels rise. It is also stimulated by other acts of love such as having sex, giving birth, and breastfeeding. It is the hormone that bonds us to our mates and to our children. But oxytocin also plays a role in intergroup conflict and violence. What?? Read on.
What is oxytocin?
It is a small peptide, only 9 amino acids long. It is closely related to another hormone that controls water balance, called vasopressin. It was the first peptide hormones to be synthesized, a feat which earned Vincent Du Vignaud the 1955 Nobel Prize. Having dispensed with this historical factoid, let’s see what it does; and here, the list, in ascending order, will warm the cockles of your heart.
- It increases contractions of the uterus during childbirth.
- It also increases the release of milk in the lactating mother. Its synthesis in the brain (in a structure called the hypothalamus) is actually initiated by dilation of the cervix and stimulation of the nipples. But what’s really likable about this hormone is that it establishes the bond between mother and baby.
- It has an effect on sexual intercourse, and specifically on the orgasm, especially in women. Now to be fair, most of the studies examining oxytocin’s effect on the orgasm were conducted in women, which may account for the conclusion that it affects them the most. This is called in epidemiology “selection bias”, for obvious reasons. But, consider this: Pfizer, the drug company that sells Viagra, thought they could double the addressable market by selling it to females. They stopped the trial prematurely because most of the females did not show any improvement in their sexual experience. The company realized that unlike males, where erection and coitus are pretty much mechanical, females are a lot more dependent on factors like mood, romantic feelings etc. In other words, as opposed to guys, it is in their head, or brain, to be more specific.
Here is Wikipedia on the subject:
“Oxytocin evokes feelings of contentment, reductions in anxiety, and feelings of calmness and security around the mate. In order to reach full orgasm, it is necessary that brain regions associated with behavioral control, fear and anxiety are deactivated; which allows individuals to let go of fear and anxiety during sexual arousal. Many studies have already shown a correlation of oxytocin with human bonding, increases in trust, and decreases in fear. One study confirmed that there was a positive correlation between oxytocin plasma levels and an anxiety scale measuring the adult romantic attachment. This suggests that oxytocin may be important for the inhibition of brain regions that are associated with behavioral control, fear, and anxiety, thus allowing orgasm to occur”.
Why stop at the woman-man or mother-infant level? Oxytocin also promotes ethnocentrism. No, I am not being politically correct here. If we define ethnocentrism as the tendency to view one’s group as centrally important and superior to other groups, it becomes a lot more familiar and somewhat less objectionable. Don’t we instinctively favor our family members over complete strangers in terms of willingness to help, in terms of leniency over transgressions, etc? But wait, can’t we expand this to a larger tribe? Do you root for the home team, or are you completely objective about it? Do you favor the news reporting on CNN over Al-Jazeera? Of course, you are tribal, admit it! It is natural; it is probably hard-wired in your brain.
When our ancestors lived in small family-centric bands, do you think they welcomed an approaching unfamiliar band with chants of “kumbaya?” This attitude of wariness, or outright hostility, is not exclusively human; a female chimp or lioness who tries to join a new troop or pride, respectively, is certain to be met with a violent welcome by the female members. Whatever the threat may be—from food resources to the chance to pass on the DNA—tribalism is deeply rooted in us.
The moral dilemma
Let me pose a question widely used in experimental psychology: Suppose you are in control at a switch of a railroad track that can divert an oncoming out-of-control train to the right track, or the left. Now, to your horror, you spot a group of 5 adults sitting on the right track and one man on the left. Which way are you going to divert the train? Tough choices, none of them good, but most people with an intact brain would choose saving five lives and sacrificing one. But here is another version: there are five Arab-looking men on the right and one American-looking one on the left. Is this choice as hard for you? Honestly, no. Likewise, many Pashtuns in Afghanistan hate what their fellow tribesmen, the Taliban, are doing to them, but would they betray them to the Americans? The answer is a resounding no. This is tribalism in action. What does all this have to do with the “love hormone”? Read on.
The other face of oxytocin
Oxytocin, as it turns out, is more of a two-faced Janus than a seductive Aphrodite. In double-blind, placebo-controlled designs, Dutch males self-administered oxytocin or placebo and privately performed computer-guided tasks to gauge different manifestations of ethnocentric in-group favoritism as well as out-group derogation. The Dutch investigators (Carsten K. W. De Dreu, PNAS online edition, Jan 10, 2011) asked their subjects to resolve a moral dilemma, such as choosing to save five lives from a runaway train by sacrificing one life. Placebo–sniffing males favored the Dutch over the foreigners, but only to slight, non-statistically significant degree. But when the same men were sniffing oxytocin, their choices were clear-cut: Oxytocin-sniffing Dutch men more often saved fellow countrymen over Arabs and Germans than those who didn’t get a hormonal whiff. As the authors note:
“Results show that oxytocin creates intergroup bias because oxytocin motivates in- group favoritism and, to a lesser extent, out-group derogation. These findings call into question the view of oxytocin as an indiscriminate “love drug” or “cuddle chemical” and suggest that oxytocin has a role in the emergence of intergroup conflict and violence.”
Does it make sense?
I think it makes a lot of sense. Biology is operating on a system of negative feedback. When we have too much carbon dioxide in the blood, we stop inhaling and start exhaling, and when our oxygen level becomes low, we inhale again. This is controlled by centers in the brain stem, some increase inhalation and some exhalation. It’s all in balance. Sounds almost Buddhist—Ying and Yang. Or American—checks and balances.
Our social interactions are, likewise, controlled by hormones to keep us balanced. Altruistic sharing of resources with your own band members increases the chances of survival of each. Naïve acceptance of all comers to share in the meager resources of the hunter-gatherer band can spell its extinction. Too much indiscriminate love for all comers can wreak havoc on the chances of a female to pass on her DNA.
This is a central tenet of natural selection. Strike one for Darwin, again.
This post is an update from the original posted on 1/16/11.