Scientists have something of a reputation for being know-it-alls. The more complex the field, the higher the pedestal on which the scientists are placed—or climb. The pedestal may then become a soapbox from which to proclaim what the scientist knows, or thinks he knows. An entertaining example is that of Nobel Laureate Kary Mullis, who claims in his autobiography, Dancing Naked in the Mind Field, to have received a communication from aliens in the form of a green glowing raccoon. More troubling for Christians is neuroscientist Sam Harris' claim—in his recent book Free Will—that free will is an illusion because we can't understand it in scientific terms.

Thus it is refreshing to find a scientist—specializing in neuroscience, no less—who approaches his field with intellectual humility. Stuart Firestein, a professor at Columbia University, was frustrated after teaching a class on cellular and molecular neuroscience. Why? The information dump gave the students the impression that science is all about accumulating facts to be neatly explained in textbooks, and that neuroscientists have the brain more or less figured out. In response to his frustration, Firestein created a new class, "Ignorance," in which various scientists describe what they don't know but are trying to find out.

Real scientists, Firestein argues, are motivated by what they don't know, and good science uncovers more questions than it answers. Science is a never-ending task and often a frustratingly difficult one. Or, as Firestein puts it, "it is very difficult to find a black cat in a dark room—especially when there is no cat." Scientists may think they have found the cat, and then years later, someone does another crucial experiment that puts us right back in the dark room, looking for a cat that may or may not be there.

Firestein's book is divided into two sections. The first is a series of essays on ignorance : what constitutes high-quality ignorance, the limits to what we can know, and some brief examples. The second half of the book is dedicated to a number of extended examples of practicing scientists. The most interesting of these are drawn from Firestein's own field of neuroscience.

Firestein points out the tendency to compare the brain to the most complicated technology available—hydraulics or mechanics in the past, computers or the internet today—and then introduces theoretical neuroscientists Larry Abbot and Stefano Fusi. They are interested in memory, in particular the kind of memory that comes easily. We see an image, even briefly, and we will recall it as familiar if we see it again. Humans can recall thousands of images in this way. Neuroscientists have proposed that human memory works like computer memory. That is, the synapses of neurons are analogous to switches in a computer. But when Abbot and Fusi modeled the brain, with its 100 trillion synapses, as if it worked like computer memory, they found that it could hold 36 memories at the most. This example makes Firestein's point well—the research revealed our ignorance, but in a way that is tantalizing to the scientist who wants to know how memory really does work. Firestein's ideas about how science works will strike most scientists as obvious. But his examples are interesting enough to keep those already committed to his thesis turning the pages, and for the non-scientist he offers a valuable counterbalance to know-it-all scientists and the portrayal of science by the media.

Jennifer Gruenke is associate professor of biology at Union University.

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