About Rationally Speaking

Rationally Speaking is a blog maintained by Prof. Massimo Pigliucci, a philosopher at the City University of New York. The blog reflects the Enlightenment figure Marquis de Condorcet's idea of what a public intellectual (yes, we know, that's such a bad word) ought to be: someone who devotes himself to "the tracking down of prejudices in the hiding places where priests, the schools, the government, and all long-established institutions had gathered and protected them." You're welcome. Please notice that the contents of this blog can be reprinted under the standard Creative Commons license.

Thursday, February 02, 2012

The mismeasure of neuroscience

by Massimo Pigliucci

These days you can’t turn around without bumping into yet another news story about “the neuroscience of X.” Some of it is fascinating, some controversial, and quite a bit of it is, well, let’s say at the very least, misguided. Julia and I have already done a couple of Rationally Speaking podcasts touching on this subject (one on Cordelia Fine’s “Delusions of Gender” and one on what we term “neurobabble”), and no doubt there will be plenty of occasions to do more.

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.


  1. I agree with everything you said, but I wish that you bounded your conclusion epistemically; you left the door open for all kinds of magical thinking.

    Our decisions are entirely accounted for by environment and the mind. The mind is entirely accounted for by genetics, the brain, and environment.

    If you fully understand the brain you can fully understand its output if you fully know its input. It's like knowing what a TV will output given you know what signal is being inputted.

    Even if you don't fully know the inputs, if you know what's in the black box, you can largely predict the output.

    This is what fields like sociobiology, neuroeconomics, affective neurobiology, behavioral neurobiology, comparative neuropsychology, and quantative genetics do or at least are in the process of doing.

    1. How can you be so certain that the mind is entirely accounted for and perfectly predictable by science? Science can't even predict the results from much simpler systems such as the double slit experiment, the position of an electron, or the timing of the decay of a radioactive substance. Do we know for certain that the mind couldn't possibly be influenced by a random effect similar to the the types of systems I have listed?

      Look, I have great admiration for Science, but there ARE some things that Science just can't link causally. And these are things that are unknowable in principle, not just things that are inconvenient to determine. Just about everyone here on this blog seems to ignore that fact and speak as if Science can predict the results from any system where the intial state and inputs are known. Or, if predictions can't be made, they assume that the events are still linked causally in principle. But that's not true! God DOES play dice with the universe! Try to predict when a radioactive substance will emit its next alpha particle or link the emmision to some prior event. Isn't the human mind more complex than a gram of U235?

    2. Yes, Tom, a brain's more complex than a gram of U235, but that complexity serves to organize it and CONTROL randomness

    3. The idea that we can fully understand the output of the brain if we understand its input is a valuable methodological assumption. It is far from a verified fact.

  2. I think the main problem is that the technology of fMRI is so advanced and produces spectacular pictures that people are so tempted to overstate what they see. It's also important to remember that in most publications, the colorful picture that we see is not from a particula person but an average of all the subjects which usually makes it look nicer. And the media too love these studies..

  3. I agree with Massimo that showing the physical (in this case neurological) correlate (or "material aspect") of a behavior is not equivalent to reducing this behavior to a mere illusion or epiphenomenon. That applies not only to neuro theories, but to many other themes (is grasping an apple "merely" a matter of oxidizing glucose in the mytochondria of certain muscle cells making those cells produce some proteins that cause the muscle mass to change its properties in a certain way? Is water "just" oxygen and hydrogen? Are biological entities "just" a mass of chemical substances, or physical sub atomic particles?).

    But I wonder on the adequacy of Massimo's argumentative strategy in this matter. We know so little about neuroscience (despite its spectacular advances) that "explaining" complex phenomena like consciousness or free will is for now just not feasible; we should try something more simple, like the molecular pathways for the consolidation of short term memories; see for instance, although too enthusiastic to my taste, the work of John Bickle and his "ruthlessly reductive" approach in his book "Philosophy and Neuroscience", esp. ch. 2: he does not discuss great things, such as "who's in charge", only very small ones, apparently those where neuroscience is more sure of itself. And he tries to go beyond "neural correlates" to study (in the lab) actual molecular pathways that "cause" such memories to exist and persist, using "cause" in the same sense that a punch in a nose causes the nose to bleed.

    Likewise, discussing what science journalists or "science activists" like Sam Harris think on grand themes is beyond the point: the scientific basis in this matter is not yet at the stage of enabling a layman-level valid discussion of its long-range implications for broad issues like free will or morality; it is, for now, a dull matter of small lab experiments and results, with actual scientific claims not going much beyond the results themselves.
    Scientists (even those directly engaged in the research) may of course be carried away by the possible hypothetical headline-worthy implications of their work, but the work itself is not about those implications, and their opinions on those "grand" themes are as valid as somebody else's.

    The slow accumulation of unpretentious results, and the gradual clarification of methodological and theoretical issues posed by that work, would probably lead "thinkers" to rephrase some of their philosophical ideas, even on grander subjects, and enable also lay persons to do the same, just like Einstein's theories did in the 1900s or Copernicus' in the 1500s, but the basic science is initially not so grand or pretentious. If your run-of-the-mill science journalist or moral philosopher of 1953 read the actual papers by Watson and Crick about DNA and extract some long-range implications for bioethics or the nature of mankind, they would have been befuddled by a mass of technical details beyond their comprehension, and not remotely touching on those grand themes.

    In short, I would advise sticking to small things for the moment. Great things will come in due course.

  4. Perhaps the distinction between meaning and referring will be useful? For example, although it is true that "the morning star" and "the evening star" have different meanings yet they both refer to the same thing, viz., Venus. And "Samuel Clemens" and "Mark Twain" refer to the same witty writer, but it seems odd to say that "my memory of Mom" and "the firing of synapse 547" refer to the same thing!

  5. Ray Tallis, a retired clinical neuroscientist, has written eloquently about this tendency (he calls it "neuromania"). For a quick summary see this recent article in The Chronicle of Higher Education.

  6. The correlation business has two flaws, one at each end of the correlation. Their structure is like this: brain state A correlates with behavior B. That's because A and B were each identified or described independently of the other, and then: "Aha! They are correlated!" But to show any causal connection, neuroscientists should be able, given only A, to predict correctly and in detail what B was, or vice versa. Eg. "this brain state shows that the subject was explaining the 2nd step in Euclid's proof that there is no greatest prime number - in Chinese." A claim that anything remotely like that could someday be done is mere naive hand-waving.

  7. I also find this sort of research unenlightening because these are just correlations with places. How much do we really understand about some type of thinking only from knowing where it happens? It's like people saying we now understand banking because we know it happens in the bank. To me, it's still a complete mystery how the brain really works.

  8. Phiwilli and kczat,
    much of the "neurobabble" is about correlations, but not all. There is some work that elicits more than mere correlations, in the sense of specifying molecular pathways that provide some physical grounds for causal inferences.

    On the other hand, a lot of science is built on correlations. For instance, astronomers estimate the distance of stars based on so-called cepheid (oscillating) stars, because they ASSUME that their period of oscillation is associated to their true luminosity, so the apparent luminosity is in that case an indicator of distance; however, the relationship is not exact; and for distant galaxies, it is worked out through correlation between period and apparent brightness of the faint cepheids that are barely visible in those galaxies. Both the original assumption and the resulting calculation of distance is based on correlation and regression (in LINEAR correlation and regression, at that). No astronomer questions that theory, on the other hand, even if none has a clue as to why period and luminosity should be causally related in cepheids. This is not to start a discussion on astronomy, just to show that correlation has a prominent place in many disciplines, especially when the underlying physical mechanism is not fully understood.
    Besides, sometimes a causal relation may be inferred even without knowing the underlying mechanism. This is the case, for instance, of brain lesions associated to certain psychological problems like aphasia or inability to identify faces: this is not a definitive proof that a lesion in a certain part of the brain CAUSED the emergence of the problem, because the mechanism or causal pathway is not known, but often offering very strong evidence of it for most practical purposes. For many years, the link of tobacco and lung cancer was denied by the tobacco industry precisely because it was "merely" a correlation, but the evidence was equally strong, and was later confirmed by the discovery of the causal links.

  9. 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

    Yes, exactly! That brain is (part of) me. It is not only some molecules following physical laws, it is also, at the same time me making a decision, thinking or receiving information. One could just as well say that a monitor displaying text is an illusion because look, it is "really" only photons being emitted. Astonishing how many people have problems with the concept of emergent properties and conceptualizing different levels of physical reality.

  10. Many years ago, I conducted a meta-study of split-brain research, and was astounded by the blanket conclusions drawn by researchers on patients who had had the corpus callosum severed (leaving intact four other connections between the two hemispheres). The presumption (without much evidence) was that, because the corpus callosum provided the largest connection between the two hemispheres, if you tested responses rapidly enough, you could isolate them to one or another hemisphere. In all likelihood, techniques have improved over the past 30 years, since I looked at the experiments, but even assuming they have, lessons from split-brain testing are of only limited value for the reasons Pigliucci suggests (e.g., because all of the subjects suffer from a pathology).

    More generally, however, while we should not put too much stock in existing neuroscientific studies of the brain and human behavior, we should also bear in mind that such studies are, to all extents and purposes, in their infancy. As technologies and methods improve, there is reason to hope that neuroscience will provide value insights towards a better (if necessarily incomplete) understanding of human cognition and behavior.

  11. 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

    One claim is based on all the applicable data observed, and the other is a nonsense. The point isn't that the left hemisphere "interpreter" is unaware of what is going on over the other side: we already agree that there is plenty of unconscious mental activity going on in intact brains all the time.

    It is that the other hemisphere is engaging in complex activities like reading and responding to commands in a "conscious" fashion, and giving different answers based on different perceptions; recognizing self; carrying out moral judgements, but not as well as the left hemisphere does. Further, if we don't put these individuals in unusual setups (separating visual information to the different hemispheres etc), we would conclude they have a normal unitary consciousness.

    We then integrate these observations with other lesional studies, as is exemplified in the SEP "Unity of Consciousness" article, to see if we can discern a common pattern.

    Turk et al's [2003] interpretation of these same data is:
    "The left hemisphere [interpreter] [...] creates a unified sense of self [that can be] realistic, [or in the example above], can verge on fantasy. However, in all cases, this left hemispheric interpretation results in a unified sense of self, even in the disconnected brain."

    I don't know if a unified sense of self is the same as a unified consciousness, however.

    1. And we also do not know whether such "unified sense of self" is based on something "real" or is just a "sense" or "sensation" caused by a plurality of processes going on in the brain. When we speak of "a sense of self", is the mere "sense" of self the "reality" we seek, or we are looking for something more "real" than the mere "sense" of self?

      In cases concerning external things, the "sense of thingness" we get from our perception may or may not coincide with something real existing and having the features that we "sense" it has. Sometimes we make perceptive mistakes about the external world (e.g. taking some inanimate process, like the wind moving leaves, as evidence of the presence of someone), and also about other minds (believing someone is in love with us, when that someone regrettably isn't). Perhaps we may make such sort of mistake about our own self? Believing it is "there" when it is only something analogous to leaves rustled about by the wind? Worse mistakes are part of our common experience, even about ourselves. Or is perhaps the existence of one's self "proved" by the fact that we have a "sense of self"? What else, if anything, is needed, precisely (underline "precisely")?

  12. Now I'm not a neuroscientist and perhaps I've misunderstood but I think there is something to the research on split-brained patients you talked about.

    You're right in that it's not normal for people to have the two halves of your brain separated from each other and the brain can't be expected to act - as a whole - as normal. Surely though if the two halves are otherwise functioning normally it could be informative to watch how they act and interact in the unusual circumstance. The fact that each half will fill in the blanks when separated does at least show we've got that capability to gloss over missing information, why shouldn't that happen when the halves are re-connected? I'm guessing the messages don't make it across from one half to the other 100% of the time and I'm guessing that one half of the brain might not always have the information the other half has requested even if the messages are transmitted flawlessly.

    I agree with you about the "just an illusion" thought though, just because you can explain something on one level doesn't change it on another which seems to be a mistake people often make. Everything has an explanation - even though it's often far out of our reach - that doesn't make it somehow less real. By that illogic only the completely uninformed are living in reality.

  13. With the incredible advances made recently into the understanding of the brain, neuroscientist have been prone to assume that they can explain everything. I am not convinced that neurosciences can give an exhaustive account of human consciousness or creativity for instance... I recently watched a fascinating debate about the power and limits of neuroscience with neuroscientist and Oxford scholar Colin Blackmore amongst other things.
    Hope it can contribute to the discussion!


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