Zombie Neuroscience

October 14, 2014

In an opinion piece in the New York Times Sunday Review (October 12, 2014, p. 12), Michael Graziano asks “Are We Really Conscious?” His answer is that we are probably not conscious. If his theory is right, our belief in awareness is merely a “distorted account” of attention, which is a reality that consists of “the enhancing of some [neural] signals at the expense of others”.

This distorted account develops in all of us, and seems to us to be almost impossible to deny. But beliefs that the Earth is the center of the universe, that our cognitive capacities required a special creation, and that white light is light that is purified of all colors, have seemed quite natural and compelling, yet have turned out to be wrong. We should be skeptical of our intuitive belief that we are conscious.

In short, Graziano is saying that your impression that you are conscious is likely a false belief. “When we introspect and seem to find that ghostly thing –awareness, consciousness, the way green looks or pain feels – our cognitive machinery is accessing internal models and those models are providing information that is wrong.”

One might well wonder what is supposed to be “ghostly” about the experience of green you think you have when you look at, say, an unripe banana, or a pain that you might believe occurs when you miss a nail and hit your thumb with a hammer. But, of course, if you are already convinced that there are no such things, then you must think that their apparent presence is merely the holding of false beliefs. If you then try to say what these false beliefs are beliefs about, you will be hard pressed to produce anything but ghosts. There are, of course, neural events that are necessary for causing these allegedly false beliefs about the way bananas look or pains – but these beliefs are not beliefs about those neural events, nor are they beliefs about any neural events at all. (People believed that unripe bananas looked green and that they had pains long before anyone had any belief whatsoever about neural events.)

Graziano’s positive story about awareness is that it is a caricature: “a cartoonish reconstruction of attention” (where, recall, attention is enhancement of some signals at the expense of others). This description raises a puzzle as to what the difference is between a cartoonish reconstruction of a signal enhancement that is caused by light reflected from an unripe banana, and a cartoonish reconstruction of a signal enhancement caused by a blow to your thumb. But perhaps this puzzle can be resolved in this way: The banana causes enhancement of one set of signals, the blow to the thumb causes enhancement of a different set of signals, and which false belief you acquire depends on which set of signals is enhanced.

A problem remains, however. Your beliefs that you are experiencing green or that you are in pain are certainly not beliefs about your signal enhancements. They are not beliefs about wavelengths or neural activations caused by blows to your thumb (though, of course, wavelengths and neural activations are among the causes of your having beliefs about what colors or pains you are experiencing). There is nothing else relevant here that Graziano recognizes as real. Your false beliefs are beliefs about nothing that is real.

We can, of course, have beliefs about things that are not real – for example, unicorns, conspiracies that never took place, profits that will in fact never materialize. In all such cases, however, we can build the non-existent targets of the beliefs by imaginatively combining things that do exist. For example, we have seen horses and animals with horns, so we can build a horse with a horn in our thoughts by imaginative combination.

But green and pain are not like unicorns. They have no parts that are not themselves colors or feelings. There are no Xs and Ys that are not themselves colors or feelings, such that we can build green or pain in our imagination by putting together Xs and Ys. So, if we were to accept Graziano’s dismissal of color experiences and pains as unreal, we would have to allow that we can have beliefs about things that neither exist, nor can be imaginatively constructed. We have, however, no account of how there could be such a belief. The words “way green things look” and “pain” could not so much as mean anything, if we suppose that there are no actual examples to which these words apply, and no way of giving them meaning by imaginative construction.

Graziano invokes impressive authorities – Copernicus, Darwin, and Newton – in support of skepticism about intuitions that once seemed incontestable. (See list in the second paragraph above.) He presents his theory as coming from his “lab at Princeton”.

The view he proposes, however, is not a result supported by scientific investigation. It is supported by the other authorities to which he appeals – Patricia Churchland and Daniel Dennett. These writers are philosophers who offer to solve the notoriously difficult mind-body (or, consciousness-brain) problem by the simple expedient of cutting off consciousness. Voilà. No more problem.

But it is not good philosophy to affirm a view that commits one to there being beliefs of a kind for which one can give no account.

It is important to understand that resisting the dismissal of consciousness is fully compatible with affirming that there are indeed neural causes for our behavior. Hammer blows to the thumb cause neural signals, which cause reflexive withdrawals. Somewhat later, the interaction of these signals with neurons in our brains causes behaviors such as swearing and taking painkillers. But hammer blows to the thumb also cause pains. It is indeed difficult to understand how or why pains should result from neural events that such blows cause. But it is not a solution to this problem to dismiss the pains as unrealities. Nor is it true that science teaches us that we ought to deny consciousness.


Mind the Gut

September 19, 2011

Johan Lehrer’s Wall Street Journal column for September 17-18, 2011 reports a fascinating pair of facts – and then makes a puzzling application of them.

The first fact concerns probiotic bacteria, which are often found in yogurt and other dairy products. Researchers provided mice with either a normal diet, or a diet rich in probiotic bacteria, and then subjected them to stressful situations. The mice with the probiotic-enriched diet showed less anxiety and had lower levels of stress hormones.

By itself, this result is not so interesting. After all, it could be that the probiotic bacteria affect digestion, then blood chemistry, and finally hormone levels. But the second fact shows that a different mechanism is at work.

The second fact is that when neural connections between gut and brain were severed, the probiotic-enriched diet no longer produced the effect of reducing symptoms of stress. This fact suggests that the effect of the difference in diet works directly through the gut-brain neural connection, rather than through a less direct blood chemistry path.

It’s as if we have a sense organ in our gut that feeds into an evaluative system. It doesn’t give us any sensations, but it tells our brains how things are in our digestive systems. If things are going well down there, we’re less prone to anxiety when stressful situations arise.

That’s a surprise that contributes to a sense of wonder at how deliciously complex unconscious processes can be. Lest one think that this has nothing to do with us, Lehrer also reports a study that showed an analogous result in human subjects who received large doses of probiotics for a month. (No cutting of nerves in that case, of course.)

Now for the puzzling conclusion. These and other studies are taken by Lehrer to show that “the immateriality of mind is a deep illusion. Although we feel like a disembodied soul, many feelings and choices are actually shaped by the microbes in our gut . . . . ” And, although he concedes that “This doesn’t mean, of course, that the mind-body problem has been solved”, he goes on to declare that “it’s now abundantly clear that the mind is not separate from the body . . . . Rather, we emerge from the very same stuff that digests our lunch.”

But “shaped” is one of the many words that mean “caused”, with the addition of something about the manner of causing (as in “burned” or “built”), or degree of causal contribution (as in “influenced” or “forced”). What the cited research shows is that causes of anxious behavior and hormone levels include the presence of probiotic bacteria in the gut, and that the means of that causal contribution works through a neural connection. That is surprising and fascinating, but it offers no evidence whatsoever that feelings of anxiety are the same things as any material events.

In general, causes and effects are different. From “How anxious you feel depends in part on what kind of bacteria you have in your gut” it does not follow that feelings are material – only that feelings, whatever they are, can be caused in a very surprising way.

Similar remarks apply to “emerge”. Different people use this word in different ways, so it’s not a very helpful term. But one of its meanings is “causes”. Yes, it is indeed fascinating that what’s in our gut can cause how we feel, and do so through a direct, neural pathway. But no, that does not show that feelings are material events. It does not show that immateriality of feelings is a deep illusion.

For some purposes, the point I’m making may not matter. It’s an important fact that what goes on in our consciousness is brought about by events in our neural systems, and the studies Lehrer cites in this article do help drive that point home. But when the mind-body problem is introduced into the discussion, it becomes important to distinguish between the views (1) that neural events cause mental events such as feelings and (2) feelings are the same things as neural events. The evidence Lehrer cites in his article support (1), but are silent as regards (2).

[Jonah Lehrer, “The Yogurt Made Me Do ItThe Wall Street Journal, September 17-18, 2011, p. C12.]