On the blog, I have criticized Sam Harris for making unwarranted statements concerning alleged scientific solutions to moral issues, which he largely bases on new findings from neurobiology (I know he has a new book on free will! Can’t wait!). And of course I keep promising an in-depth analysis of Alex Rosenberg’s new book on atheism and reality (a review will soon appear in The Philosopher’s Magazine, stay tuned).
It’s not that I don’t like neuroscience, on the contrary, it is precisely because I’m fascinated by the new discoveries, and because of the respect and love I have for science, that I think people do a disservice to the whole enterprise when they make claims that are simply unsubstantiated by the available evidence (or, worse, when they incur category mistakes, like Harris’ confusion between facts and values).
Fortunately, not everyone falls prey to easy sensationalism about neuroscience. For instance, I am in the process of reading (for a forthcoming review in Skeptical Inquirer) Michael Gazzaniga’s new book, Who’s in Charge? Free Will and the Science of the Brain (yes, I know, free will!), and I find the author to be eminently sensible about the whole thing. Not only does he knows his stuff, he also knows where to draw the line between science and speculation, and the book is peppered with a good dose of philosophically sophisticated reasoning (just like another of my favorite neuro-authors, Antonio Damasio).
Nevertheless, there are two general issues that I’m concerned about whenever discussions of “the neuroscience of X” come up: one has to do with an apparent confusion (in some people’s minds) regarding what exactly one establishes when one discovers a neural correlate for a particular human behavior; the other has to do with what can (and cannot) be learned from studies of brain damage, be it accidental or as the result of surgery to alleviate neurological problems.
Let’s begin with what exactly follows from studies showing that X has been demonstrated to have a neural correlate (where X can be moral decision making, political leanings, sexual habits, or consciousness itself). The refrain one often hears when these studies are published is that neuroscientists have “explained” X, a conclusion that is presented more like the explaining away (philosophically, the elimination) of X. You think you are making an ethical decision? Ah!, but that’s just the orbital and medial sectors of the prefrontal cortex and the superior temporal sulcus region of your brain in action. You think you are having a spiritual experience while engaging in deep prayer or meditation? Silly you, that’s just the combined action of your right medial orbitofrontal cortex, right middle temporal cortex, right inferior and superior parietal lobules, right caudate, left medial prefrontal cortex, left anterior cingulate cortex, left inferior parietal lobule, left insula, left caudate, and left brainstem (did I leave anything out?).
I could keep going, but I think you get the point. The fact is, of course, that anything at all which we experience, whether it does or does not have causal determinants in the outside world, has to be experienced through our brains. Which means that you will find neural correlates for literally everything that human beings do or think. Because that’s what the brain is for: to do stuff and think about stuff.
This does not at all mean that I don’t find these studies fascinating, they surely are. But they are answering a different question from the one that often gets pushed in news stories. Specifically, what neuroscientists are finding is how the brain does X, which constitutes an explanation of X only in a very limited and specific sense of the word “explanation.” Take moral reasoning as an example. What “explains” it? Well, at the neurobiological level, it is the result of the action of the above mentioned brain areas (and probably many more). Evolutionarily speaking, a sense of morality probably evolved to help large-brained primates deal with their social environment. Culturally, our sense of morality has evolved in different directions at different times and in different places (though with some interesting convergences). Sociologically, what is moral depends on a complex interaction between fundamental human needs (like the need to feel safe) and idiosyncratic rules adopted by certain groups of people for entirely arbitrary reasons (like those regulating the Sabbath). Which means that the neuroscience of X is a fascinating but very limited part of the larger puzzle comprised by the broader question of “what is X?” And it behooves us to keep this distinction in mind.
The second issue that I see recurring in news or popular coverage of neuroscience is the one about what exactly we learn when the brain malfunctions. V.S. Ramachandran has written a whole mind boggling book on this sort of research, but perhaps the most spectacular of these case studies are those concerning so-called split-brain patients. As is well known, these are situations in which the corpus callosum, the tissue that normally mediates communication between the right and left hemispheres of the brain, is severed because of accident or surgery (usually to ameliorate epilepsy).
The above mentioned Gazzaniga is one of the leading experts on split-brain research, and he is very careful when he draws conclusions from what he observes in these patients. Nonetheless, it is not at all uncommon to hear people jump to the conclusion that these experiments show that the unity of consciousness is an “illusion” (a word which Rosenberg, for one, is surely fond of: it recurs a whopping 100 times in his book, in different but related contexts), and that our much vaunted rationality is really rationalization. These two notions arise from the experimental observation that split-brain patients are literally “of two minds,” since the experimenter can communicate with the right and left hemisphere separately, often obtaining contradictory or incongruent answers. Moreover, when the left hemisphere (which is in charge of spoken language) is asked to explain the incongruities, it simply makes stuff up by connecting the available evidence in an apparently coherent story. Gazzaniga refers to the left hemisphere as “the interpreter,” the structure that is in an important sense in charge of our conscious view of the world.
But observations of split-brain patients — as captivating and scientifically informative as they are — do not at all warrant the above mentioned conclusions. Remember that split-brains are not normal, they are a pathology. Pathologies do tell biologists something about how things work, but they certainly do not tell them the “real” nature of a biological process any more than a mutation tells geneticists the “real” structure of an organism’s trait. Let’s try to draw the analogy in a bit more detail. Biologists have discovered that a mutation in a particular gene causes a condition known as phenylketonuria. If you are affected, you absolutely need to stay away from the amino acid phenylalanine, which is found in a variety of foods, including soda drinks (next time you drink one, check the label, it has a warning to phenylketonurics).
Now imagine how ridiculous a geneticist’s statement would be if he said that the biochemical pathway that metabolizes phenylalanine is “really” an illusion, as demonstrated by the phenotype (the manifestation of phenylketonuria) that we observe in patients with the mutation. If you think this analogy is outrageous I’d like you to explain to me exactly why. In both cases one takes an individual with a pathology and uses his behavior to conclude that what appears to be normal is actually illusory, and that the pathology is a better guide to what’s “really” going on.
The same reasoning can be applied to the confabulation of the left hemisphere “interpreter.” Yes, the experiments do show very clearly that if the left hemisphere doesn’t have access (because of the severed corpus callosum) to the information coming from the right hemisphere, it makes stuff up in order to make sense of what it knows. This does not mean that we confabulate and rationalize all the time, it means that when our brains are fed bad information they weave it together the best they can. This surely has all sorts of implications, including for public education, but we have to keep in mind that we are observing a maladaptive behavior caused by a malfunction of the brain. We are not therefore licensed to conclude that it also malfunctions under normal operating conditions.
So, the next time you hear someone say that moral decision making is “just” your brain working, ask them what else could possibly generate that behavior, and whether that’s all there is to know about this crucial ability shared by all non-psychopathic human beings. And when someone tells you that consciousness is an illusion because split-brain patients have lost their unity of mind, ask them if they are also comfortable in drawing the conclusion that metabolic defects are the real way human biochemical pathways function. That ought to generate some interesting discussion.