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.
Such biases can affect how we see other people. We humanise those who are part of the same group, ascribing a more complex range of emotions to them. By contrast, we have a tendency to dehumanise outsiders, by assuming that their emotional lives are narrower. This particularly applies to so-called “secondary emotions”, such as admiration, hope or embarrassment, which are seen as unique to humans (in contrast to “primary emotions” like happiness, fear or disgust that are common to other animals).
De Dreu found that oxytocin strengthens these tendencies. He asked 66 white Dutch men to sniff either oxytocin or placebo before showing them pictures of other Dutch or Middle Eastern people. The volunteers had to say how strongly the people in the images would experience different emotions. Both groups were more likely to ascribe secondary emotions to people within their group than those outside it, but that difference was even greater after a sniff of oxytocin.
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 last experiment clearly shows a trend that applied to the whole study: oxytocin boosted favouritism for people who belong to the same group. Only very rarely did it increase negative feelings towards people outside it. For example, in the moral dilemmas, oxytocin made the volunteers less likely to sacrifice members of their own group, but not more likely to sacrifice outsiders.
Ich finde das Experiment interessant, weil es einmal eine direkte Auswirkung von Oxytocin auf die Entscheidung des Menschen darstellt (was allerdings auch bereits in anderen Studien erforscht wurde, und zum anderen, weil es deutlich macht, dass Oxytocin nicht einfach so Zuneigung hervorruft, sondern diese einen konkreten Bezug haben muss.
In dem Experiment zeigen die Leute unter Oxytocineinfluss nicht ein moralisch besseres Verhalten, sondern sie bewerten Personen, mit denen sie eine gewisse Zugehörigkeit verbindet (und sei es nur eine gemeinsame Kultur), positiver und wichtiger. Vielleicht kann man dies übersetzen mit
„Wenn es dir gut geht (Oxytocin wird ja gerade in diesen Momenten ausgeschüttet), dann handele zu Gunsten derer, mit denen du vertraut bist“.
Ich könnte mir vorstellen, dass sich ein solches Verhalten im Rahmen der Evolution durchsetzt, weil es eben eine Schicksalsgemeinschaft bildet und man sich unlogisches Verhalten gerade in Zeiten, in denen es einem gut geht, auch eher erlauben kann.
Der Forscher, de Dreu, meint, das Oxytocin zu einer „tend and defend“-Strategie führt:
Humans regulate intergroup conflict through parochial altruism; they self-sacrifice to contribute to in-group welfare and to aggress against competing out-groups. Parochial altruism has distinct survival functions, and the brain may have evolved to sustain and promote in-group cohesion and effectiveness and to ward off threatening out-groups. Here, we have linked oxytocin, a neuropeptide produced in the hypothalamus, to the regulation of intergroup conflict. In three experiments using double-blind placebo-controlled designs, male participants self-administered oxytocin or placebo and made decisions with financial consequences to themselves, their in-group, and a competing out-group. Results showed that oxytocin drives a “tend and defend” response in that it promoted in-group trust and cooperation, and defensive, but not offensive, aggression toward competing out-groups.
Wenn man dann hinzurechnet, dass Östrogene die Wirkung von Oxytocin verstärken sollen, dann könnte dies vielleicht auch erklären, warum Frauen im Gegensatz zu Männern im Schnitt Partner gleicher Hautfarbe bevorzugen.