The Difficulty of Loving Strangers

Editor's Note: The accuracy of the italicized portion of this story has been questioned.

Over at Not Exactly Rocket Science, Ed Yong has a great post on a new study looking at oxytocin, a brain hormone that's typically associated with feelings of trust and love. The hormone pours into the bloodstream, for instance, during childbirth, triggering contractions and child-mother bonding. (Synthetic versions of oxytocin, such as pitocin, are used to induce labor.) In recent years, the chemical also been linked to Prairie vole monogamy, increased generosity in the Ultimatum Game and trusting behavior when making risky investments. Such research has led, inevitably, to idiotic products like this:

This new study, however, complicates the feel good narrative. It turns out that oxytocin isn't simply a chemical version of social affection. Here's Yong, summarizing the work of Carsten de Dreu at the University of Amsterdam:

De Dreu asked 280 Dutch men to take three puffs form an oxytocin nose-spray, or a placebo that contained the same mixture without the hormone. It was a “double-blind” study – neither de Dreu nor the men knew who had been given what until the results were in.

First, de Dreu looked for any hidden biases in the volunteers’ reactions to German, Arab or other Dutch men. He used an ‘implicit association test, where volunteers used two keys to categorise words into different groups (e.g. Dutch names or German/Arab names, or positive and negative). Combinations of categories that contradict our biases should subtly slow our reaction times. If people are biased against Arab people, they’d take longer to finish the test if the same key was assigned to both Arab names and positive words. These “implicit associations” are very hard to fake, especially if the test is done at speed.

Sure enough, oxytocin strengthened the biases of the Dutch volunteers. When they sniffed oxytocin (rather than the placebo), they were quicker to associate positive words with Dutch names than with either German or Arab ones.

Finally, de Dreu showed that these shifting biases could affect the moral choices we make. He presented volunteers with a famous series of moral dilemmas. For example, a runaway rail trolley is hurtling towards five people who are about to be killed unless you flip a switch that diverts the trolley into the path of just one person. All of the dilemmas took the same form – you weigh the lives of one person against a group. And in all the cases, the lone person had either a Dutch, German or Arab name, while the group were nameless.

After a sniff of placebo, the Dutch volunteers were just as likely to sacrifice the single person, no matter what name they had. But after sniffing oxytocin, they were far less likely to sacrifice the Dutch loners than the German and Arab ones.

This suggests that the feelings of trust and warmth triggered by oxytocin come with a hidden cost, in that we become less likely to trust "outsiders." Although the chemical sharpens our positive feelings towards those we already know and understand, it also exaggerates the perceived differences between our in-group and everyone else. There is no love for all.

This shouldn't be too surprising. One of the endlessly repeated lessons of the human brain is that it's a finely equilibrated machine, full of carefully engineered compromises and tradeoffs. As a result, many of our attempted "enhancements" come with a steep cost, triggering a raft of unintended side-effects. And this isn't just true for the chemicals of social cognition. Last year, in an article in Nature, I wrote about thirty-three different rodent strains that show dramatically enhanced learning and memory. The genetically tweaked animals can learn faster, remember events for longer and are able to solve complex mazes that confuse their ordinary littermates. At first glance, these strains seem like the rodent of the future, a case-study in the infinite possibilities of cognitive enhancement. When you look closer at the mice, however, it becomes clear that many of these animal mutants display subtle negative side-effects. Consider a strain that overexpresses adenylyl-cyclase in the forebrain: Although the mice exhibit improved recognition memory and LTP, they show decreased performance on memory extinction tasks. (In other words, they struggle to forget irrelevant information.) Other strains of “smart mice” excel at solving complex exercises, such as the Morris Water Maze, but struggle with simpler conditions. It’s as if they remember too much.

And then there’s “Doogie,” the rodent strain named after the fictional television prodigy Doogie Howser. These mice overexpress a particular subunit of the NMDA receptor, known as NR2B, which allows their receptors to stay open for twice as long as normal. The end result is that it’s easier for disparate events to get linked together in the brain. The only downside is that Doogie mice also seem to suffer from increased sensitivity to chronic pain. Their intelligence literally hurts.

And these tradeoffs don’t just exist in mice. In the early 1920s, the Russian neurologist A.R. Luria began studying the mnemonic skills of a newspaper reporter named Sherashevsky, who had been referred to the doctor by his editor. Luria quickly realized that Sherashevsky was a freak of recollection, a man with such a perfect memory that he often struggled to forget irrelevant details. After a single read of Dante’s Divine Comedy, he was able to recite the complete poem by heart. When given a random string of numbers hundreds of digits long, Sherashevsky easily remembered all the numbers, even weeks later. While this flawless memory occasionally helped Sherashevsky at work – he never needed to take notes – Luria also documented the profound disadvantages of such an infinite memory. Sherashevsky, for instance, was almost entirely unable to grasp metaphors, since his mind was so fixated on particulars. “He [Sherashevsky] tried to read poetry, but the obstacles to his understanding were overwhelming,” Luria wrote. “Each expression gave rise to a remembered image; this, in turn, would conflict with another image that had been evoked.”

For Luria, the struggles of Sherashevsky were a powerful reminder that the ability to forget is just as important as the ability to remember. What might seem, in the abstract, like an astonishing gift turns out to actually be a curse.

And this returns me to oxytocin. For years, we've heard about this chemical that seems to magically turn us into a better version of ourselves: more loving, more trusting, more human. And yet, all those emotional benefits come with some pretty devastating fine print. We might feel closer to our friends and family, but we are farther away from everyone else.