Catherine MacBride/Getty Images
Catherine MacBride/Getty Images
If you stop and think about it, the idea that you could understand a complex system by detailed description of one its parts is crazy on the face of it.
You are unlikely to get too much insight into the principles organizing flocking behavior in birds by confining your attention to what is going on inside an individual bird. And you aren't very likely to figure out how birds fly in the first place by studying properties of the feather.
The second example is due to vision science pioneer David Marr, and was advanced by him in the context of his rejection of neural reductionism in the theory of vision. To understand how we see, he believed, you need to think about what an animal does when it sees. What is the task of vision? What is vision for? Only then, given a description of the phenomenon couched at the level of the animal and its needs and interests, can we intelligently ask: How might we (or how might nature) build an animal or a machine capable of performing or implementing this function? And only then would we be in a position to ask, of individual brain cells, what sort of contribution do they make, or do they fail to make, to the achievements of the whole.
It is amusing that Marr's book was published just as David Hubel and Thorsten Wiesel won the Nobel Prize for their work on information processing in the mammalian visual system. Their achievement — building on the work of generations of scientists — was to discover receptive fields of cells in the cat and monkey. In lay terms, they found that different cells were tuned to be more responsive to one kind of stimulus rather than another (lines, bars, motion). They neither asked nor answered the looming question: How do circuits of individual neurons manage to give rise to conscious visual experience? That the question has an answer — that some version of the reductionist story can be made out — was probably taken for granted not only by Hubel and Wiesel, but by those who judged their work worthy of the highest prize in science.
In fact, we still don't understand how visual consciousness arises in the brain. And we can return to Marr's book for an understanding of why this might be. You just can't read off the achievements of the whole — not the brain, or the whole organism — from facts about what is going on with individual cells. A lot of conceptual spade work needs doing before facts about receptive fields can be taken to contribute to the understanding or explanation of anything at all.
I and others have been making this argument for some time with little discernible influence on the general hype. (See here, here and here.) The Year of the Brain, the Decade of the Brain, the Connectome, the Brain project, etc. So it is an event of considerable note — maybe one of genuine historical importance — that a group of top neuroscientists from around the world have recently come together to write an opinion piece in the journal Neuron calling on neuroscience to "correct its reductionist bias" and embrace a "more pluralistic neuroscience."
Hubel and Wiesel, remember, won their prize for single-cell electrode studies on the brains of cats and monkeys. The only other tool for studying the brain then available was post-mortem autopsy. Since then, there has been an explosion of techniques and technologies for studying the brain of living humans and other animals: fMRI, PET and other imaging tools, but also even newer techniques of genetic manipulation and ontogenetic circuit control. Join these new technologies of discovery with big data and increased computing power and you've got, in a way, a perfect storm — or, rather, a recipe for a theoretical or explanatory dead end. More information is not the same as more knowledge, and data untrammeled by understanding, by sound theory and by the big picture is just noise. Actually, it's worse than noise. It's noise masquerading as insight.
Everyone knows you can't find consciousness in the individual cell. But we now have tools for modeling temporally and spatially distributed ensembles of cells. Surely we'll find the key to mind there, in those larger groupings! Until we know what questions to ask, we're unlikely to find anything. (Or rather, we'll find something but lack a clue what it is, as when Columbus landed in the Americas but thought he'd made it to India. I give this example because Hubel compared his research with Wiesel to Columbus's explorations in his 1981 Nobel Prize lecture.)
John Krakauer et al, who wrote the piece in Neuron, are not pessimists — not any more than Marr was. To move forward and understand the human mind, or the minds of nonhuman animals, they propose, we need to look outside the brain at the animal's behavior, that is, at how animals live, what they do, what problems they face, and what the circumstances are in which they thrive. There's more to biology than molecular biology, and there's more to cognition and consciousness than neural activity. We won't understand how the brain enables mind until we think more carefully about behavior.
Philosophy is not — and has never been — the cognitive property of philosophers. Science needs philosophy, both in the sense that scientists ought to pay attention to what philosophers are doing, but even more importantly in the sense that scientists, at least sometimes, maybe in moments of crisis, need themselves to do philosophy. They need, themselves, to question their presuppositions and do the hard conceptual spade work to set themselves on more reliable foundations. I applaud these scientists for their appreciation of the value, for their science, of the need to frame and better contextualize their own research methods.
Science has never been just about information or data. Science aims at understanding, at knowledge. By calling for a rejection of simple-minded reductionism and by encouraging brain scientists to think again about the conceptual puzzle of understanding the relation between the life of an organism and what is going on around it, as well as inside of it, these neuroscientists are taking important strides towards setting up an adequate neuroscience of cognition and consciousness.
Alva Noë is a philosopher at the University of California, Berkeley where he writes and teaches about perception, consciousness and art. He is the author of several books, including his latest, Strange Tools: Art and Human Nature (Farrar, Straus and Giroux, 2015). You can keep up with more of what Alva is thinking on Facebook and on Twitter: @alvanoe