You’ve gotta’ love human fairness—that highest of our species impulses, the ineffable sense of what’s right and what’s wrong, rising straight from our good and decent hearts. Maybe. Or maybe what we think of as fairness is just the result of a little jolt of current, firing away in a single region of the brain—the right lateral prefrontal cortex (rLPFC)—a phenomenon no more poetic than the natural insulin hit your body gets after you eat a sugary snack. Where’s your human exceptionalism now?
That reductionist view of our noble nature comes from a new study published in the journal Science, which sought to determine both how inclined we are to behave fairly, and how that inclination changes when there are potential consequences for the choices we make. In both cases, electricity in the brain played a role.
The study, conducted by researchers at the University of Zurich and the University of Vienna, involved 63 female subjects who agreed to participate in a simple sharing game. (A single-sex model was chosen to avoid the confounding effects of sex-linked behavioral differences.) In all of the rounds of the game, one participant, Player A, was given a certain number of Money Units (MUs) that could be cashed in for real money at the end of the study, and was told to share as much of it as she chose with Player B. Ideally, she would choose 50%, but humans aren’t ideal creatures, and the average gift ranged from just 10% to 25%. In other rounds with other participants, Player A was asked to do the same, but Player B was then free to reduce Player A’s stake by as much as she chose. With that kind of accountability in place, the initial parceling of the pot evened out considerably, with Player A giving from 40% to 50% away. OK, so not much of a surprise—but then things got more complex.
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In later rounds, the same test was run, but in these, the game was played while Player A was having her rLPFC (which had been identified in earlier magnetic resonance imaging studies as playing a role in fairness behavior) lightly electrified by trans-cranial direct current stimulation (tDCS), a procedure in which very low levels of current are administered through scalp electrodes to selected brain regions. The earliest use of tDCS was as a form of therapy for people who have suffered strokes or other brain injuries, though later studies have shown that the stimulation might also enhance performance on some cognitive tasks. (There are few side effects from tDCS, but some people do report dizziness or nausea.) The subjects in the joint Zurich-Vienna study were administered one of two types of tDCS: anodal—which increases brain activity—and cathodal, which decreases it. Some subjects were also administered placebo stimulation that did nothing at all.
The subjects’ performance clearly reflected the kind of stimulation they were receiving. Women getting the brain-boosting anodal stimulation increased their giving by 33% over the original average in the accountability version of the game; women receiving cathodal stimulation decreased giving by 22.7%. The placebo group was effectively unchanged. In the rounds in which Player A could not be punished for possible greed, the results were actually reversed: generosity fell under anodal stimulation and rose under cathodal.
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To get a sense of how much all of this was governed simply by a desire to maximize the amount of money amassed, and how much might have been influenced by our innate desire not to be thought ill of by the other player, the researchers recruited a second round of 59 women and administered the exact same test, but this time they were playing against a computer. With or without brain stimulation, the women gave almost nothing to their nonhuman opponent. When it was possible the machine could take some kind of revenge by clawing some of the money back, the players were a little more equitable, but not as much as they’d been with human opponents, even when brain stimulation was used.
None of this is to say that outside the lab, human fairness is controlled simply by random bursts of electricity in the brain—some days you get a little more and some days you get a little less, in the same way that some days your blood pressure is higher than others for myriad chemical reasons. We are still responsible for—and the authors of—our own generosity. Like all living things, we may just be just be gooey machines. But we’re still machines capable of choosing to do good and noble—or bad and ignoble—things.
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