Paul Glimcher Discovers Neurological Underpinnings of ‘A Beautiful Mind’

By John Beckman

Over 400 years ago, the metaphysician Rene Descartes developed a theory of how the brain functioned by dividing behaviors into separate types: the “simple” and the “complex.” The simple were those in which a sensory event provoked an automatic motor response while the complex were less predictable, involving what Descartes called the “soul,” but what scientists would later refer to as cognition and volition.

This model of brain study has dominated neuroscience for 400 years. But Paul Glimcher, associate professor of neuroscience in NYU’s Faculty of Arts and Science, and a group of like-minded psychologists, economists, and neurobiologists believe that this dualistic theory of how the brain processes behavior can be advanced into a singular one.

Their goal? Build an original cognitive theory that can be applied to every type of decision-making. Their medium? The mathematical tools of economics and game theory, the insights of social psychology, and the mechanistic tools of modern neuroscience.

Recently, Glimcher and former NYU colleague Michael Dorris offered neurobiological evidence that may elucidate a basis for the economic theories of John Nash, the Nobel-winning economist who pioneered game theory, in an article in the Oct. 13 issue of the journal Neuron.

The findings in the Neuron article are a major advancement in the increasingly prominent field of neuroeconomics, which attempts to discover the basis within the brain for the sort of economic decision-making predicted by game theory. In addition, Glimcher, along with University of Minnesota economist Aldo Rustichini, authored a major review article on the state of and potential for neuroeconomics, titled, “Neuroeconomics: The Consilience of Brain and Decision,” in the Oct. 15 issue of the magazine Science.

To develop their findings, Glimcher and Dorris, who is now at Canada’s Queen’s University, used rhesus monkeys to participate in a strategic conflict game known as the “the inspection game” (first developed by the RAND Corporation to evaluate the likelihood of Soviet compliance with arms control agreements). In the human version of the game, there are two players—an “employer” and an “employee.” The employee’s goal is to “shirk” as much as possible (for which he receives his wage plus free time), while the employer — who can use an “inspector” to catch the employee — has the goal of spending as little as possible on inspectors while maximizing the employee’s appearances at work.

John Nash, whose life and work was detailed in the movie and book, A Beautiful Mind, developed a theory that predicts outcomes in this kind of strategic setting. Glimcher and Dorris sought to test those predictions with experiments on both humans and rhesus monkeys, and to examine in the monkeys whether there was evidence that decision-making became encoded within the posterior parietal cortex of the primate brain.

Dorris and Glimcher found that with human players the outcomes predicted by the Nash equilibrium computations were largely correct and, surprisingly, that the behavior of the monkeys in this game was essentially identical to that of the humans. This was an important finding because it permitted the researchers to examine the role of the posterior parietal cortex of the monkeys in a setting in which the monkeys seemed to employ similar, if not identical, strategies as humans in game playing.

Another element of Nash’s theory opened the door for Glimcher’s and Dorris’s neurological findings. In Nash’s theory applied to the inspection game, the “desirability” of the employee’s two options, working or shirking, must be equivalent regardless of the level at which the equilibrium is achieved. Glimcher and Dorris reasoned that if the economic theory was sound in terms of producing behavior, then there should be corresponding neurological findings in the posterior parietal cortex.

In fact, when Glimcher and Dorris examined the activities of those neurons while the monkeys played the inspection game, they found that the posterior parietal cortex carried a signal essentially identical to the one expected. When the monkeys’ behavior was well predicted by Nash’s theory, the neural activity corresponded.

In Science, Glimcher and Rustichini outlined how economics, psychology, and neuroscience are today converging into a unified field that may soon provide a singular theory of human behavior. Although they admit that it remains to be seen just how complete the theory will eventually become, they note that neuroeconomics experiments are already proving fruitful in fusing natural and social science. The goal, says Glimcher and Rustichini, is to develop a neuroeconomic program that offers a “mechanistic, behavioral, and mathematical explanation of choice that transcends the explanations available to neuroscientists, psychologists, and economists working alone.