Say you have a load of donated food to deliver to an orphanage in Uganda. But due to circumstances beyond your control, you're forced to make a hard choice: give some of the children enough meals to stave off hunger for several days and let the rest go hungry, or evenly distribute a smaller amount of food so that each child feels full for just a few hours. A study published online today in Science is one of the first to investigate how the brain wrestles with such morally charged tradeoffs.
Ming Hsu, a behavioral economist now at the University of Illinois, Urbana-Champaign, and colleagues Cédric Anen and Steven Quartz at the California Institute of Technology in Pasadena, California, used functional magnetic resonance imaging (fMRI) to monitor brain activity in 26 volunteers as they grappled with a version of the orphanage conundrum. The researchers told the subjects they'd arranged to donate 24 meals to each of 60 children at a real Ugandan orphanage, but that some of the meals would have to be taken away. Inside the fMRI scanner, the volunteers then made a series of decisions between pairs of options shown on a computer screen: One option would take a number of meals away from a single child, and a second option would split the loss between two children. Volunteers might be given the choice, for example, of taking 15 meals from child A and taking seven and eight meals away from children B and C, respectively.
When the total number of meals was the same in the two options, as in the example above, people almost always chose to make two children share the loss, Hsu says. But as the number of meals taken away from the two children increased--and exceeded the number that one child would forgo--people tended to change strategies, taking 15 meals from A, for instance, instead of nine meals each from B and C. This strategy lessens the overall impact, Hsu explains. The findings suggest that people strive to avoid inequity, but only up to a point; maximizing the greater good is also an important--and sometimes competing--factor in such decisions.
The fMRI scans contain hints of how these two factors might be encoded by the brain. The insula, a brain region linked to processing emotion, became more active when subjects considered more inequitable distributions of meals; it was also more active in subjects whose choices suggested a greater-than-average aversion to inequity. Activity in another region, the putamen, seemed to track the common good, rising in proportion to the total number of meals that could be donated in a given case. At the end of the study, the researchers donated $2279--the monetary equivalent of all the meals donated by the experimental subjects--to the orphanage to use however it saw fit.
"The main strength of the paper is that they're able to isolate two different moral motivations" and investigate how they are represented in the brain, says Jorge Moll, a neuroscientist at Labs D'Or Hospital Network, a private medical and research institute in Rio de Janeiro, Brazil. Moll points out that subjects struck various balances between avoiding inequity and maximizing the common good, and he wonders whether the balance might differ across different cultures as well, with some valuing equity among individuals over the common good, or vice versa. Hsu says he's now testing that hypothesis in experiments with Asian, European, and American volunteers.