In the experiment the participants had to lie down next to each other in parallel brain scanners. They were asked to perform the same task simultaneously. Dots appeared on a screen and they had to estimate the number being displayed. They were then told whether their answer was correct. If they had solved the task correctly, they received a financial reward, which might range from 30 to 120 euros. Each participant also learnt how his partner in the game had performed and how much he would pocket in return.
Throughout this procedure the tomograph monitored the changes in blood circulation in the different regions of the subject's brain. "We registered enhanced activity in various parts of their brains during the test," explains the Bonn neuroscientist Dr. Bernd Weber. "One area in particular, the ventral striatum, is the region where part of what we call the 'reward system' is located."
The reward system is activated when an individual has an experience he considers worth aspiring to. "In this area we observed an activation when the player completed his task correctly," says Bernd Weber, who heads the NeuroCognition Imaging group at the Life&Brain Institute. „For us, however, the exciting finding was the role played by another factor: the performance of the player in the other scanner. Weber's colleague Dr. Klaus Fließbach sums up the outcome, "Activation was at its highest for those players who got the right answer while their co-player got it wrong."
The researchers then took a closer look at those cases in which both players estimated the number of points correctly. If the participants received the same payment there was relatively moderate activation of the reward centre. But if player one was given, say, 120 euros, while his partner received only 60, the activation turned out to be much stronger for player one. For player two, on the other hand, the blood flow into the ventral striatum actually decreased â€“ even though he had performed the task successfully and had been rewarded for his efforts.
MEDICA.de; Source: University of Bonn