Friday, March 21, 2008

Brain Bubbles

My sister-in-law recently sent my spouse and me a pointer to a a video by a neuroanatomist, referenced in TEDBlog. My beloved played this thing, and I heard the speaker, Dr. Jill Bolte Taylor, start to describe the brain and its hemispheres, the right one, which "functions like a parallel processor," and the left, which "functions like a serial processor." With growing apprehension, I heard her say,

Our right human hemisphere is all about this present moment…. It thinks in pictures …. Information in the form of energy streams in simultaneously through all of our sensory systems, and then explodes into this enormous collage …. I am an energy being connected to the energy all around me through the consciousness of my right hemisphere. We are energy beings connected to one another through the consciousness of our right hemispheres as one human family….

This is the problem with having two computers in the same room; sometimes one spouse starts to run an audio the other really didn't want to hear. (Hey, who knew that the Voyeurweb tittie cam even had audio?) As Dr. Taylor waxed more and more ecstatic about the right hemisphere, I tried to stifle a rising urge to shout, "This is utter crap!," but I was not successful. Meanwhile, an essay on one brain hemisphere must be followed, as the night the day, by an essay on the other:

Our left hemisphere … thinks linearly and methodically. Our left hemisphere is all about the past and it's all about the future. Our left hemisphere is designed to take that enormous collage of the present moment and start picking out details…. It then categorizes and organizes all that information, associates it with everything in the past we've ever learned, and projects into the future all our possibilities. And our left hemisphere thinks in language. It's that ongoing brain chatter that connects me and my internal world to the external world. It's that little voice that says to me "Hey, you gotta remember to pick up bananas on your way home…." It's that calculating intelligence that … reminds me when I have to do my laundry. But perhaps most important, it's that little voice that says to me, "I am; I am." And as soon as my left hemisphere says to me "I am," I become separate, I become a single, solid individual, separate from the energy flow around me, and separate from you….

At this point I had to leave the room, because I really couldn't interrupt my spouse's session with Dr. Taylor with a spell of badgering about how absurd the good Dr.'s descriptions were.

Dr. Taylor is a neuroanatomist, who, according to her website, "specializes in the postmortem investigation of the human brain." Fine; I'm sure she knows her way around dead brains like the back of her hand. But her knowledge of the living variety has apparently been garnered from the same pop-psych books that just about everyone seems to have absorbed and believed unquestioningly. You know the type: They promise to help you unleash the potential of your right brain, which processes information "nonlinearly," and so can help you think outside the box.

There is a grain of truth in these theories, and that is that in most people language is mostly processed in the left hemisphere. Damage to certain areas results in linguistic deficits that are by now somewhat predictable, although by no means understood.

That's about all we know that is relevant to the issue at hand, regarding differences in processing abilities in the two hemispheres. In particular, spatial reasoning and other sorts of nonverbal abilities do not show any asymmetry; they are, as far as anyone can tell, carried out by tissue distributed across both hemispheres. The mechanisms of consciousness, described in authoritative tones by Dr. Taylor, are still controversial, but all the proposed "neural correlates" of consciousness do not show the sorts of asymmetries she takes for granted.

Indeed, the only reason that I have ever been able to glean for the near-universal opinion that the left hemisphere is "serial" and the right "parallel" is the assumption that language is serial in a way that other human capacities are not. This assumption is derived from the obvious fact that words are spoken, and heard, one at a time, and that deciphering the meaning, and intelligibility, of a sentence depends upon assembling the words into sentences that preserve the order in which the words were uttered. At a cocktail party, you may or may not succeed in isolating the words one person is saying, but if you don't you will hear a meaningless babble.

Furthermore, many people are insecure about, shall we say, their "debating skills." They may have strong opinions about, for instance, capital punishment, but faced with an argument that conflicts with those opinions they often just get frustrated. I say "they," but I think everyone has been in this position at one time or another. It's comforting for us to think that we have arrived at our opinion "holistically," whereas our opponent is good at thinking "linearly." The opposing argument is, after all, stated in the form of an argument, whereas what we have is a cloud of opinions that we feel must be justified somehow. Wouldn't it be great to think that there are merely two styles of thinking, each valid in its own way, and that the one we use transcends the stifling linearity of argument and arrives at a deeper truth while at same time connecting us to all the other "energy beings" who agree with us?

When you add it all up, it's a mighty slim set of reasons to believe some patent absurdities, which I will try to refute:
  • The left hemisphere does not "think in language." The ability to produce and understand language may or may not reside entirely in the left hemisphere, even if much of it does, in most people. But to suppose that the thinking required to understand language is itself transacted in language is a ridiculous case of circular reasoning.
  • The brain is a parallel processor, all over. It has billions of neurons that generally find something to do most of the time. This is just as true of the left hemisphere as the right. Think about it: In a sizable fraction of people the language areas are in the right hemisphere; if a child suffers an injury to their left hemisphere, the right one can often adapt. Would that mean the right hemisphere turns serial?
  • There is nothing serial about language, or at least what we normally think of as "linguistic thinking." The standard example of "linear" thinking is a mathematical proof. But even if a proof is linear, that doesn't mean the thinking required to find or understand the proof is linear. At the very least there are many blind alleys in searching for a proof, and you can't really understand the proof without reproducing some of that search.
  • People who claim that language is "linear" are overlooking poetry and fiction. Texts in these forms are sequences of words just as much as proofs are, but no one would believe that writing or understanding a poem is just a matter of grasping one word after another.
  • We do not become "separate...individuals" because an inner voice says "I am." To believe that is to believe that there weren't any separate individuals until the evolution of language. I'm guessing individualhood is as old as the first cell. Of course, consciousness didn't come along until later, but most of us believe that dogs and chimpanzees are conscious, and they don't have inner voices speaking English to them.
The truth is, we know remarkably little about how the brain thinks, in spite of much recent progress in neuroscience, and hullabaloo about techniques such as fMRI. Nonetheless, people like Jill Bolte Taylor love their preconceptions, and it will be a long time before they stop speaking as though there were evidence to back them up.

No comments: