Top-Down Control?

October 20, 2010

In a recent paper, distinguished neuroscientist Chris D. Frith calls attention to a simple but arresting point: “there are no brain areas that have only outputs and no inputs”. Instead, every area that provides its output to other areas also receives inputs from other areas (as well as feedback from areas to which it sends output).

For example, if we act, the motor neurons that drive our muscles fire. Areas in which these motor neurons lie receive input from areas that lie a little farther forward in the brain. These more forward areas receive input from an area still farther forward (the prefrontal cortex), which receives input from many other areas, and so on. We never come to an outputter whose activity is not conditioned by inputs from elsewhere.

The context for this point will be clear from the article’s title: “Free Will and Top-Down Control in the Brain”. Frith contrasts top-down control with bottom-up control. The “bottom” is sensory inputs and in bottom-up control, action is driven by sensory inputs. Reflexes would be the clearest sort of case: if your knee is tapped in the right way, your lower leg will move as a direct result of the tap.

In contrast, Frith takes top-down control to occur when goals or plans are involved in actions. A key point is that goals or plans do not depend directly on what we are immediately sensing. Which food you purchase for dinner may well depend on the quality of what you see in the grocery store, but your goal to get some food did not depend on what you were seeing or hearing when you went to the store.

Your goal to get food did, however, depend on conditions somewhere in your brain, and if there is no area that is solely an outputter, the goals you have are the result of contributions from many brain areas. In Frith’s thinking, a true “top level” would be a brain area that affects other brain areas, but is not affected by other areas. The significance of the fact that all brain areas receive inputs from other areas is that there is no “top level” in this sense. There is no unaffected effector from which our goals emanate.

Frith sees this fact as a problem for locating free will in an individual. His view seems to be that free will requires a top level that is only a top level, i.e., is not affected by anything else. “Nothing must control the controller.” Since there is no top level of this kind in the brain, we cannot find a physiological area in an individual person that provides free will.

One might draw the conclusion that there is no such thing as “free will” if this term is understood to require a top level that has no inputs. That would, of course, leave open the possibility of offering some other conception of “free will” that would not imply a requirement that we know is not satisfied.

Interestingly, that is not the conclusion that Frith draws. Instead, he considers experiments on free actions. Typical tasks in these experiments include moving one’s finger whenever one wishes to do so; or moving the right or left index finger, whichever one wishes, in response to a signal; or generating a series of “random” digits. Frith notes that results in such experiments depend on a social interaction between participants and experimenters – the latter give instructions, and the participants cooperate in agreeing to try to follow them.  So, he says, “The top-down constraints that permit acts of will come from outside the individual brain. . . . If we are to understand the neural basis of free will, we must take into the account the brain mechanisms that allow minds to interact”.

This does not seem to be a happy solution to the problem as Frith sets it up. That’s because social interactions plainly do not provide a “top level” in the sense of something that gives outputs but receives no inputs. Participants and experimenters are themselves subject to many social influences; there are no people who give outputs to others but receive no inputs from others.

It seems that a better conclusion to draw from Frith’s reflections is that there is no “free will” in the sense of an outputter that has no inputs. If there is such a thing as “free will” at all, there must be some other way of conceiving what it amounts to.

[The paper from which I’ve quoted is Chris D. Frith, “Free Will and Top-Down Control in the Brain”, in Murphy, N., Ellis, G. F. R., and O’Connor, T., Downward Causation and the Neurobiology of Free Will (Berlin: Springer-Verlag, 2009), pp. 199-209. Frith attributes the simple point with which this post begins to another distinguished neuroscientist, Semir Zeki.]

Do We Control Our Daydreams?

September 20, 2010

I’ve been reading Paul Bloom’s How Pleasure Works (New York & London: W. W. Norton, 2010), and ran across the arresting statement that “in a daydream you have perfect control” (p. 200).

Readers of Your Brain and You will recognize that this claim goes against the grain of chapter 5. But quite independently of the reasons given there, daydreaming seems a poor candidate for something we control. After all, daydreaming is supposed to be relaxing and pleasant. When we’re daydreaming we are not trying to do much of anything – we are taking a break from our effortful projects. In daydreaming, as Bloom also says (p. 198), our “minds are wandering”. But wandering – as we might do, for example, in a park – is exactly not trying to get anywhere in particular. If we are not aiming at some particular result, or series of actions, or series of mental images, it seems odd to think of ourselves as in control of what images come to mind. 

The puzzle I want to address today, however, is that what Bloom says seems initially plausible, even to me. Why should that be? Why should it seem natural to say we are in control of our daydreams when, on reflection, that does not seem to be so?

Part of the explanation is that Bloom describes daydreaming as involving “the creation of imaginary worlds” and portrays us as designers, casting directors, and screenwriters of these worlds and of the “imaginary beings [that we create] to populate” them (p. 198). But these descriptions actually apply to creators of fiction, i.e., writers of stories, novels, and plays. Such writers are not daydreaming: they are trying to do something, namely, to write a story that will be dramatic, convey a moral, tell us something about ourselves, and so on. They may have many ideas cross their minds, and they exercise control when they reject most of them as not contributing to the drama or atmosphere at which they are aiming. But trying to write a good story is not what we’re doing when we are daydreaming, or letting our minds wander.

A deeper clue comes from a contrast that Bloom draws between normal daydreaming and some cases of schizophrenia, “in which this other-self creation is involuntary and the victim of the disease believes that these selves are actual external agents such as demons, or aliens, or the CIA” (p. 198).

This contrast seems real. But “involuntary” does not seem to be the best description of it, since what occurs to us in normal daydreaming does not seem rightly described as “voluntary”. “Voluntary” actions are actions you consider beforehand and decide to do. But we do not set about trying to bring certain images to mind when we daydream – we relax and they come to us unbidden.

A better description of the contrast is that when we daydream, we have a palpable sense that the images we entertain are ours. This is not control, but something more like ownership. We do not control what comes into our minds, but we do have a sense that we are actively picturing to ourselves, and this is not just like passively perceiving something in the world outside our bodies.

This kind of active involvement seems similar to what happens in our inner speech. When we talk to ourselves, we have auditory imagery that is like hearing what we say to ourselves. But we also have a palpable sense that we are saying something to ourselves, and not merely hearing something being said. To lose this sense would be to “hear voices” – which would be disturbing, and a sign of illness.

The resolution of my puzzlement, then, is this. In daydreaming, we have a sense of active involvement in picturing to ourselves. We feel that our images are our images, something we produce. In many other cases, when we produce something, we have control over the character of what gets produced. So, our active involvement in picturing to ourselves is easy to confuse with control. But “producing” our images in this sense is not the same thing as controlling which images are popping up in our mind’s eye. Projectionists at your local theater are actively involved in producing the images on the screen, but they do not control the character of those images.