While the findings are clearly intriguing, it's not yet clear what they mean. One popular theory of autism is that people with the disorder lack a normal theory of mind--the ability to imagine the thoughts and actions of others. Identifying a specific deficit linked to thoughts of self could help narrow down what has gone wrong in that process. "People think autism is linked to a lack of understanding of what a partner is doing," says Chiu. "But maybe they don't understand their own role in the social exchange."

Other scientists interpret the results further, suggesting that this signal is linked to a sort of internal reputation assessment in the brain. "If you are a normal person, when you invest money in the game, you are thinking about how you will look in the eyes of your partner," says Frith. "That's precisely what the theory of mind hypothesis would project is wrong with people with autism."

Other autism experts are unwilling to make such a leap. "I'm skeptical about how much [the Baylor College study] tells us about which capacities are intact and engaged in autism," says Matthew Belmonte, a scientist at Cornell University, in Ithaca, NY. "I'm not convinced they have a deficit at all. Maybe they have adopted a different cognitive strategy."

Regardless of the deeper meaning of their findings, Montague and his team ultimately hope to develop the brain-imaging results into a diagnostic test. They have converted the activity signal from the cingulate cortex into a simple numerical score, which correlates well with a clinical test for the severity of autism. Eventually, they hope to be able to show, for example, "that if you get a 3 rather than a 14, you are 80 percent more likely to be a high-functioning autistic," says Montague. Such a tool could potentially also be used to test the effectiveness of new behavioral treatments, he says.

However, much work remains to be done before such a test could be used in a doctor's office. "We need to make it simpler and test people with a wider range of IQs," says Montague. The Asperger's volunteers in the current study had an above-average IQ.