Each subject was instructed separately in the rules of the game. One the investor received $20 during the first of the 10 rounds of the game. That person decided how much money to give the other subject. That sum was then tripled. The other subject, 1,500 miles away, decided how much of the money he or she kept and how much he or she left for the other subject. Each interaction of that type completed a round.

"What we map on are the changes in blood flow," said Montague. "Those tell us the amount of trust and trustworthiness, the degree of betrayal and benevolence."

In early rounds, Montague and his colleagues were able to identify a physical response in the brain of the trustee that correlated with the intention to increase their trust or investment on the next move. By later rounds, the timing of that response changed so that his or her intention to trust occurred before the completion of the previous round.

The technique holds promise for understanding diseases such as autism in which the ability to form models of the actions of other people is impaired. Or it might help in the understanding of maladies such as schizophrenia.

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Contact: Ross Tomlin
htomlin@bcm.tmc.edu
713-798-4712
Baylor College of Medicine
31-Mar-2005