Jonah Lehrer has a great post, The Value of Neuroscience, over at The Frontal Cortex. He writes about struggling with a common question he got during his recent tour for his new book, How We Decide.

The question is, “What practical knowledge have we gained by looking at decision-making in the brain that we didn’t already have, either through introspection or behavioral studies?”

His answer is, “The best answer, I think, is that learning about the brain can help constrain our theories. We haven’t decoded the cortex or solved human nature – we’re not even close – but we can begin to narrow the space of possible theories.”

That is both an elegant and a practical answer – it claims neither too much nor too little for neuroscience, and provides a way to think about neuroscience. Ways of thinking are often much harder to grasp than what to think, where neuroscience churns out an enormous quantity of information but not necessarily an enormous range of hypotheses about people as people.

Lehrer’s answer echoes my own view of evolutionary theory, that its greatest utility is in limiting the range of possibilities when confronting the diversity and commonality of people’s behavior lives today and in the recent past. People are often aghast when I say this – but what about all the predictions, the selective forces, Darwin’s genius? But there is evolution’s strength – certain possibilities are more likely, and others are often not on the table. Combine that with the mechanistic understandings from neurobiology–the outcomes of evolutionary adaptations and present function–and suddenly the range of possibilities is constrained further.

But the brain and evolution are both clever than you are, so its constraints are often very unlike the way we think of constraints based on favored theories and often unrecognized assumptions. So it proves useful to do two things, first to have some evidence on the introspection and behavior side.

I prefer ethnography for that, since it can be just as systematic and rigorous as a good quantitative or experimental study and provides what people say and what people do in spades. These sorts of data then provide a way to match evolutionary and neuroscientific possibilities to the real world.

For the other thing, I like Stan Katz’s recent post on The Utility of Useless Knowledge. Katz takes on the recent essays on humanities needing to justify themselves, and writes, “Until we can redefine ‘utility’ to encompass the notion that it is the full range of learning that is necessary to save ourselves, I fear we will be unable to help ourselves, the country, or the world very much.” The humanities extend our notion of self and of human nature, and combat those assumptions that evolutionary biologists and neuroscientists bring to the table. The humanities help to further define the range of possibilities.

As for answering the question Jonah got, I’d say that neuroscience has reached the stage where its consideration of processes and its focus on mechanisms and interactions help us think through problems of behavior and experience in ways that Freud and Hume and William James and Virginia Woolf could not. It’s not just the space of possibilities but how you navigate them that is important. And here neuroscience helps considerably, though obviously I think other approaches also help considerably.

One last note – the comments to Jonah’s post are fascinating, for they illustrate a range of reactions to neuroscience, from it being good to bad to interesting in itself. In one sense, they are all reactions to the perceived social utility of neuroscience today. Jonah’s point is more subtle, that we will get to some actual utility by starting to consider the range of possibilities and from there move on to forging connections to what was known before, what we work on today, and how we might address problems based on that overall process.