Is free will an illusion? How do we make decisions? What is the nature of the mind? These are some of the questions addressed in “The Neural Basis of Free Will and Consciousness,” a freshman seminar that combines philosophy and neuroscience and immerses freshmen in the theory and technology of both disciplines. Classroom lectures, group discussions, and laboratory experiments help students probe some of the most fundamental assumptions we make about ourselves as humans: that we are rational decision makers, and that we make choices based on free will.

“As an opportunity for freshmen it is off the scale,” said Michael J. Berry, associate professor of molecular biology and the Princeton Neuroscience Institute and co-director of the Program in Neuroscience. “It places them at the cutting edge of neuroscience research.”

The seminar is co-taught by Berry and Adam N. Elga, associate professor of philosophy. The class meets once a week for a lecture followed by discussions. Readings range from classic philosophy texts like Hume’s An Enquiry Concerning Human Understanding to the latest reports from the frontiers of neuroscience, such as a groundbreaking study on the delayed perception of decision making reported in the January 2009 issue of Psychological Science.

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In addition to empirical experimentation, the students debate questions of free will versus determinism, how philosophers think consciousness develops, and how to define it. They apply a philosophical approach to analyzing their readings and interpreting the scientific data from their experiments.

Princeton was one of the first non-medical facilities in the world to have a functional magnetic resonance imaging (fMRI) scanner dedicated to research. This giant magnet, which maps neural activity by measuring changes in cerebral blood flow, allows the students to observe each other’s brains in action. Their assignment is to replicate a recent neuroscience experiment on the perception of decision-making, and then take the published research one step further by designing a variant experiment of their own.

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“Princeton has very active research groups working on exactly these kinds of experiments—it is unlikely this seminar could happen anywhere else,” said Berry.

Susan G. Robison, a doctoral candidate in psychology who studies brain activity in her research on human memory, runs the fMRI lab component of the seminar and supervises the student experiments. During one experiment, Robison watches a bank of monitors and—through a window—the fMRI scanner in the next room. One monitor screen shows a well-defined human brain outlined by a faint human profile. This is Luis M. Suarez ’12, who has volunteered to be scanned. Inside the tube, Suarez watches a video screen where letters appear one by one. His task is to say what letter is on the screen when he freely decides to push a button. On the monitor, decision-making activity in his brain is visible as much as ten seconds before he is conscious of making the choice to push the button.

For neurons, ten seconds is a very long time. A neuron needs only a millisecond to fire off a message. If neurons in the brain were musicians, ten seconds would be long enough to play one of the Goldberg Variations; if a neuron could type, ten seconds is almost enough time to write the Gettysburg Address.

“Neuroscience results are so dramatic,” says Elga. “Eight to ten seconds before you feel you have made the choice, there are already conditions that are affecting your choice, determining the choice for you. What unconscious mechanisms are driving your decision? And is it still free will? For a decision to be freely made, you have to be aware of what went into the choice.”

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Suarez and his classmates bring empirical evidence from their lab work to the philosophical discussions. Suarez says he is thrilled by the research. The two professors share his enthusiasm. For one thing, the difficulty of the seminar, which admits by application only, means that the students who get in are a truly interested and motivated group. For another, interweaving the two disciplines benefits the professors as well: they are expanding their own horizons, each learning from the other’s very different approach to teaching, to research, and to thinking about the “big questions.”

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“It is important for scientists to talk with philosophers,” says Berry. Scientists, he explains, “prefer to bite off small pieces of definable knowledge” and often dismiss the mysterious, abstract questions that philosophers are trained to tackle. He believes both disciplines are necessary to advance the study of free will and consciousness. Philosophers can help scientists define the terms and understand the phenomenology of free will and consciousness, and scientists can help philosophers understand what is happening at a neural level in the brain.

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“Mind events are produced by brain events,” Berry added. “The brain is the physical substrate of the mind. By studying the neural basis of consciousness, we can address the phenomenon of consciousness itself.”

The interdisciplinary seminar is supported by funding from the David A. Gardner ’69 Magic Project, established by Lynn Shostack in memory of her late husband, a lifelong lover of magic. The project awards more than 15 grants each year to support performances, course development, conferences, and equipment for scholarly explorations relating to magic. According to Elga, magic has everything to do with a course on free will and consciousness: something as simple as raising your hand involves such a complexity of generated and transmitted information that it comes very close to magic.

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July 2009