Interview: Patricia Churchland

Nervous systems distinguish animals from all other kingdoms of life. And certain properties of the human brain distinguish our species from all other animals. The human brain is, after all, the only known collection of matter that tries to understand itself. To most biologists, the brain and the mind are one and the same; understand how the brain is organized and how it works, and we'll understand such mindful functions as abstract thought and feelings. Some philosophers are less comfortable with this mechanistic view of the mind, finding Descartes' concept of a mind-body duality more attractive. Patricia Churchland has taken center stage in this debate about the human mind.

Dr. Churchland is a professor of philosophy at the University of California, San Diego, and an adjunct professor of neuroscience at the Salk Institute. Boundaries between the humanities and the sciences dissolve as Professor Churchland attempts to synthesize a philosophy of the mind based on what neuroscience is learning about the brain. Her seminal book in this new synthesis is Neurophilosophy: Toward a Unified Science of the Mind-Brain (MIT Press, 1986). Biology is a multidisciplinary adventure that integrates the natural sciences and connects to the humanities and social sciences. Neurophilosopher Patricia Churchland is helping make those connections.

What led you, as a philosopher, to neuroscience?

The questions I was interested in as a philosophy graduate student were really questions about the human mind, about the nature of learning and perception, about what it is for something to be conscious, about the difference between the actions we call voluntary and actions we call involuntary—the free-will problem. As time went on, it became increasingly clear to me that these were really questions about the brain and that I needed to know the nuts and bolts of the brain, what neurons were and how they talked to each other. The more neuroscience I knew, the more it seemed to me that we really had the key to understanding the nature of the mind via neuroscience. That is not to say that we had a key that you could use independently of psychology — behavioral descriptions — but that it was a crucial element.

I was always unconvinced by arguments that in addition to the brain, there is a nonphysical soul, and it's the soul that makes decisions, the soul that feels and thinks. If you're unconvinced by that, then the nature of the brain and its organization have to be relevant in understanding these fundamental questions that philosophers are interested in.

How did you then begin to learn neuroscience?

Well, I knew some basic biology, basic cell physiology and biochemistry, but I realized that I needed to know brain anatomy. By this time, I was a faculty member at the University of Manitoba. So I phoned the head of the anatomy department at the University of Manitoba Medical School and explained my interests. He said, "Why don't you just come and take the basic neuroscience course with the medical students and do as much or as little as you want." I did all the anatomy and the basic physiology, but that wasn't enough. Then I got associated with a lab and learned the basic techniques, such as recording from single cells.

Was it uncomfortable for you, coming from a philosophy background, to challenge the tradition of mind-body duality?

Not for me personally, because I don't think that distinction of mind and body, or brain, ever seemed terribly plausible. I was always part of that tradition that says that complexity is not predictable from looking at the constituents, but put them together in certain ways, and you get these really extraordinary properties. The mental properties for perception, for knowledge, for learning, for memory all had to come out of the complexity of the organization of matter.

If we view the major mind functions as emergent properties of the brain organization, what do we need to understand about neural complexity to explain these mental functions?

I think the major area we're missing is at the level of neural networks. Assuming that neurons form themselves into micronets, and micronets interact with larger units, or macronets, it's really the properties at that larger level that we don't yet understand. With the advent of artificial neural nets we can design on computers, we are beginning to get at least a conceptual framework for making that bridge between the individual neurons on the one hand and the systems on the other. We have a long way to go.

Take the case of categorization, for example. Some regions of the brain seem to be specialized for categories of natural things and others for manmade things. And within the regions specialized for manmade things, there is further categorization—for example, tools that you use with your hands, and other kinds of things like automobiles. We don't know how brains do this regionalization, so we don't know how to make nets that can help us understand it. Another key question about brains is how they get things done in time. How can an eagle intercept its prey? How can you catch an outfield fly? How you get the timing right is a major issue for a lot of neural network theory now. What we desperately need is more understanding of neuroanatomy at the network level.

Modeling neural nets on a computer is one thing, but is the brain itself a type of computer?

It's useful to think of the brain as a kind of computer because that allows you a framework for thinking about how individual neurons interact to achieve a certain effect. For example, if what you are trying to do is focus on a given object and your head is turning, thinking of the brain as a computer gives you a way of understanding the interaction between the neurons in the vestibular organ, which function in the sensation of movement, and the neurons that control eye movement. But unlike a desktop computer, the very elements in the brain that process perception are also elements that store information about what you perceive. It isn't that the memory is in one place and the processing for perception is in another place. The brain is a very different kind of computer, but I find the computer to be a useful metaphor.

Do you think knowledge of the brain can enable us to build better computers or different kinds of computers?

Yes, I really do. I think that there is likely to be big technological payoff as we understand in more detail how neuronets function and how they solve problems. That is, how do they manage to be so flexible? How, with so few neurons, can a bee solve problems that are really quite complicated? In general, I think the flexibility and the capacity to generalize that we see with brains and don't see in the very brittle architecture of artificial computers are things we will understand as we get more of the story of the brain.

Do you think it's possible to build machines that think?

I think in principle it is. Since we are machines that think, and evolution built us, then yes. Whether using the kinds of components that we are now using we can mimic the brain depends on the nature of the problem. If what we want to do is get the timing right, we may have to mimic what neurons actually do down to the level of membrane proteins.

All of which depends on learning more about how the brain itself works. Are we getting closer to understanding consciousness, memory, or emotions?

We have made progress on a number of major questions—certainly on the learning and memory front, and on the interconnectedness of reason and emotion. Researchers have studied the idea that emotion and feelings—the ones we actually call gut feelings, the feeling of uneasiness or that something is wrong help bias us in ways that allow us to do the kinds of calculations we normally call pure reason. The main point is that in situations requiring a certain amount of analysis, you need not just frontal cortex but input from the limbic structures that are cued, in turn, from the viscera, the skin, and so forth. That is very revealing about the way we actually work. It shows us that for really heavy intelligence stuff—determining what, in the general sense, is relevant and what isn't—you've got to have the emotions involved. It may mean that there is something right about the strategy that people invoke when they say it's important to be in touch with your feelings. Say you come into a room and you sense something is not right. I certainly wouldn't say that it is a completely reliable clue, but it's something worth relying on for telling you to look closer, to look harder.

Is that part of what we mean by being conscious?

Some people have the idea that before you can study consciousness, you need a nice, precise, clean definition of what consciousness is. I want to resist that. Clean, nice, precise definitions are what you get after you've done the science and you've got a nice theory. Before you have a good theory, often what you have to do is go with good examples, with phenomena where you've got quite a lot of agreement. Doctors and most lay people are pretty good at telling whether somebody is in a coma or vegetative state or conscious. We're pretty good at telling when somebody is in deep sleep and when they're awake—and that's a big difference in consciousness. When you're in deep sleep, you're not aware of things, even though you may do some things that are somewhat intelligent. For example, you move a lot in deep sleep and you navigate around the bed. Even if you're in a relatively novel bed and there are other people in the bed, you generally manage to navigate. And we can tell when someone is in REM sleep, which seems to be different from both of those other states. So what we'd like to know is: what happens in the brain when somebody is in deep sleep, and when awake, and in REM sleep?

Why do we sleep?

There's been interesting recent work on the anatomy and physiology of sleep. But why we need to sleep is really puzzling. I think sleep plays a critical role; that really important things are happening seems obvious to me, but what they are, we don't know. But we do a lot of it, and we like it. People, by and large, like to sleep. There must be a significant reason why the brain does it. Some people think that it has to do with restoration of basic neurotransmitters, and that it's fundamentally a metabolic issue. That's quite possible. The startling thing that people discovered many years ago, however, is that your neurons are not quiet in deep sleep; they're going like blazes. There's very little difference between neural activity when you're in deep sleep and overall neural activity when you are conscious. Both deep sleep and REM sleep are quite puzzling because we incur a survival risk in both. We're terribly vulnerable. Evolution has put a good deal into this strategy—but exactly why, it's hard to say.

Do you see potential medical applications of neurophilosophy?

Insofar as I see neurophilosophy as a part of the general discipline of neuroscience and insofar as I see neuroscience as having a major medical benefit, then yes. There are still a number of serious medical problems we haven't quite gotten a grip on. One is schizophrenia, another is Alzheimer's, and another is Parkinson's. In all of those cases we have palliatives for treating people to make those diseases slightly less awful, but we are a long way from enabling a person to have a normal life and a normal death. When you realize that about 1% of the population have schizophrenia, and something like 15% over age 65 suffer from Alzheimer's, and something comparable for Parkinson's, it is really important to understand these diseases. I think the answers will come out of further understanding of basic neuroscience.

Unifying brain and mind may seem like a reasonable objective to most biologists. Why are some of your philosophy colleagues uncomfortable with this synthesis you call neurophilosophy?

Part of it is that science discovers that the reality behind the appearances is quite different from what we thought. Aristotle thought, for pretty good reasons, that an object is not going to keep moving unless you keep a force applied to it. Giving that up based on the Newtonian framework means accepting a very different picture of the nature of kinetics. And similarly, thinking that things come into being in a Darwinian fashion rather than at the moment of creation is, for some people, very counterintuitive. I think some people worry that the next step is that science is going to say, "You aren't what you thought you were." I think lots of us find that hard. It's one thing to have a counterintuitive theory of motion but I don't want a counterintuitive theory of myself; there can't be a counterintuitive theory of me because I'm the best authority for how I work. Also, I think some people think that if science is applied to humans, then the dignity of humans is at stake. I actually take a very different view, that some of the very damaging superstitions we have about humans may actually be replaced by much more caring, more humanitarian hypotheses or approaches, in just the way that it is really much more humanitarian to have a pharmacological way of treating a schizophrenic than to put that person on a dung pile in order to chase the demons out. As in other places in our universe, I think that a scientific understanding of the mind will actually promote humanitarian values rather than detract from them.

Maybe the other thing that worries some philosophers is that these questions about the mind have been their property for a long time. It's a turf thing. But I think the coming generation of graduate students and young faculty in philosophy find it obvious that scientific data on the brain are relevant to our understanding of the mind. In the meantime, the turf thing continues. A leading critic of neurophilosophy makes an argument something like this: Sure the brain is probably all there is, but you will never explain consciousness, the painfulness of pain, and so forth in terms of neurons, in terms of ions passing back and forth across membranes, etc. My response is, that's an argument from ignorance. That's an argument from, "I can't imagine." So what if you can't imagine it? That's a fact about you. That's not a fact about what we can and can't discover. I am unimpressed by that argument.

As neurophilosophy brings the brain and mind closer, how will this change how we view ourselves as a species?

Maybe in a general way, one could say that we are learning increasingly how much similarity there is between us and other animals. And that many aspects of our behavior are rooted in our evolutionary past via evolution of the brain. The brain has many of the aspects it has because we had to survive. We shouldn't find this alarming or sad; I think we should revel in it. But at the same time, there are things that make us different. Just as there are things chimpanzees can do that we can't do, there are things we can do that they can't do. It would be nice to know what the difference is. One hypothesis is that what makes our intelligence possible is allowing the nervous system to mature at different rates. In our case, immaturity in the brain is extended for quite a long time. And things the developing brain learned earlier can be useful in teaching the brain later. Perhaps these developmental delays enable us to do more complicated things. So it's not that we're rational, and other animals are not; it's a quantitative difference partly related to the developmental timing that prolongs brain development. That understanding might even have the effect of allowing people to have more regard for other species and less of the attitude that we are the greatest, so we get to squash all the others. Evolution doesn't start from scratch. It has to be gradual, to some degree. A small difference in some aspect of an organism can make the thing as a whole look like it's got vastly different properties. Our brains are so similar to chimpanzee brains, but some relatively small difference in developmental timing magnifies into very different properties. My guess is that the study of brain development and child psychology are where the really big action is going to be in neuroscience in the next few decades.

©2005 Pearson Education, Inc., publishing as Benjamin Cummings