The study focused on an example of decision-making called the ultimatum game, in which two strangers meet and have a chance to split $10. One person is designated the "proposer" and offers some portion of the money to the "receiver." If the receiver accepts the offer, both collect the money as proposed; if the receiver rejects the offer, neither receive anything. The game is played with the explicit stipulation that it is a one-time interaction.
Standard economic theory suggests that the proposer should always offer $1 or some minimal amount and that the receiver should always accept, preferring to receive $1 than nothing. Many previous studies, however, have shown that people often reject what they see as unfair offers, foregoing profit and denying a windfall for the other player.
In their study, the Princeton researchers asked people to play the ultimatum game while the receiver's brain was being scanned by functional magnetic resonance imaging, a technology that allows researchers to see what brain areas are active at all moments during the study. They found that the more unfair the offer, the more activity they saw in an area called the anterior insula, which is associated with disgust and other negative emotions.
Another brain area, the dorsolateral prefrontal cortex, which is associated with working memory and deliberative thought, also responded to unfair offers. When the researchers averaged the results from 19 subjects, who each played 10 rounds of the game with different proposers, they found that the activity of the emotion area exceeded that of the deliberative area in cases when the subjects rejected the offers. The reverse was true when they accepted offers.
"It is not only telling us that there is an emotional response but that there seems to be a competition between these different considerations or ways of processing the situation," said Jonathan Cohen, who directs Princeton's Center for the Study of Brain, Mind and Behavior and is a co-author of the study.
During the study, receivers rejected unfair offers about half the time, which is consistent with many published studies, said Alan Sanfey, the lead author of the study. "When we explain the game to people they often ask, 'So why would I ever reject an offer? What's the trick?' And we say, 'There's no trick; if you reject an offer you don't get any money; if you accept the offer, you get it.' And they say 'OK.' And yet when they get in there and receive an unfair offer, oftentimes they reject it. There's an element of feeling a little betrayed."
"Both the field of economics and the field of decision making have, for a long time, resisted talking about emotions," said Sanfey, a postdoctoral researcher. "Now we can show biologically that emotions are not just important in a tangential way, in that making a decision makes you feel a certain way; they are important in a primary way because a sufficiently negative emotion can induce you to make certain decisions that would seem to go against your self interest."
My guess is that this behavior is a product of natural selection because the impulse to punish people was usually played out against people with whom one would have longer term dealings. If people knew from previous experience that a person would punish people who were perceived to have acted unfairly then it was less likely that the people in a tribe or village would act unfairly toward that person. Emotions essentially were designed to provide a reward in terms of emotional satisfaction under circumstances where the act of punishing exacted an immediate objective cost on the punisher. Therefore emotions were really designed to cause us to act in our longer term self interest. Of course emotions were not flawless in their guidance in ancient times. Emotions are probably even less perfect guides to action in modern environments because we have not evolved to be adaptive to the kinds of environments we can create.
What does this have to do with the future? First of all, we are no longer in the environment we evolved in because we increasingly create our own environments. Will we create environments that are compatible with our nature? Also, the biological basis of human nature throws a light on what we might modify to become something different in the future. Germline genetic engineering will eventually produce humans who are, on average, different in how their minds work than humans now living. What problems lie in the future that are a consequence of our nature? See my previous post Altruistic Punishment And Genetic Engineering Of The Mind.
|Share |||Randall Parker, 2003 June 16 05:07 PM Brain Altruism|