Hemispheric Disturbances: On Michael Gazzaniga | The Nation


Hemispheric Disturbances: On Michael Gazzaniga

  • Share
  • Decrease text size Increase text size

Drawing on dozens of results of this kind, Gazzaniga suggests that one of the modules in the human brain should go under the name of the “Interpreter.” This system—located in the left hemisphere, along with the speech center—is what concocts a coherent narrative out of all the brain’s activity, and the annals of neuroscience are now full of bizarre neurological conditions and deft experiments that reveal this constant creative act at work. Of great importance to Gazzaniga’s argument are some oft-cited experiments purportedly demonstrating that conscious awareness of making a decision registers only after the brain has primed itself for that course of action, and sometimes even after the action has been performed. Gazzaniga calls this living in “a post-hoc world” and gives an example from his childhood in the California desert. If he jumped at a rustle in the dry grass that turned out to be nothing but a breeze, he would explain to the irritated sibling onto whose foot he had just landed, “I thought I saw a snake.” His point is that there’s actually no thinking involved in the jump: it’s a reflex, executed by his nervous system via a shortcut in the brain that bypasses the whole intricate baggage of conscious decision-making. Conscious choice takes time, and time is exactly what juvenile primates don’t have if they want to survive in a dangerous environment. But we still need to make sense of what our reflexes do, and this is where the Interpreter comes in, providing the story: “I thought I saw a snake.” According to Gazzaniga, the stories the Interpreter tells tend to be bravely forward-looking, all about steering the ship of fate into uncertain waters, equipped with free will and unity of purpose; but these parables of moral courage are no more than specious retrospective rationalizations for things we do automatically.

Who’s in Charge?
Free Will and the Science of the Brain.
By Michael S. Gazzaniga.
Ecco. 260 pp. $27.99.
Buy this book.

About the Author

Cathy Gere
Cathy Gere teaches the history of science at the University of California, San Diego.

The issue of unity of consciousness thereby leads directly to the other hoary question that drives the argument of Who’s in Charge?: How can free will exist in a deterministic world? If our brains act according to the causal laws governing all matter, in what sense can we be said to be free? And if freedom of choice is just a story we tell ourselves to make sense of our reflex actions, what happens to notions of moral responsibility? This has been a worry for philosophers for millenniums; now neuroscientists have begun to ponder what their work might mean for our cherished notions of human freedom and ethical accountability. Gazzaniga is impressed by the experiments showing that there is a crucial time lapse between our brains priming us to do something and our conscious awareness of making a decision, but he is anxious about the corrosive effect that this revelation might have on the American legal system. If we accept the implications of living in a post-hoc world, then “My brain made me do it” threatens to become a get-out-of-jail-free card available to everyone, not just to sufferers of fetal alcohol syndrome or schizophrenia.

Gazzaniga’s answer to this knotty little problem lies in his gloss on the term “emergence.” Roughly speaking, emergence tries to capture the sense in which things are more than a sum of their parts. Gazzaniga’s example is traffic. Traffic is composed of cars, and would not exist without them, but it cannot be reduced to cars, and it certainly cannot be characterized or predicted on the basis of the properties of a carburetor. It is a complex system in which weather and time of day and urban planning and individual events and scores of other elements all combine with cars to produce traffic. Traffic is traffic, and is not reducible. Similarly, Gazzaniga argues that free will does not reside in individual brains but is an emergent property of groups of brains: if brains are cars, free will is traffic. For Gazzaniga, freedom is a slightly vacuous concept. Free from what, exactly? He opines that responsibility, not freedom, is the essential concept for the continued operation of the legal system, and since responsibility has no meaning in the absence of others to whom to be accountable, it is better understood as an emergent property of social groups than as something possessed by individuals.

* * *

Gazzaniga opens up a number of intriguing avenues of inquiry with the concept of emergence, but his ideas about responsibility, though, are something of a philosophical dead end. He is so focused on the danger of letting people off the hook, he loses sight of the opposite hazard. If moral responsibility does not reside in the individual but in the existence of the group, then presumably all members of the human family are equally responsible for their actions, irrespective of their individual mental health or state of mind. So keen is he to evict individualism from our notions of responsibility that he cites statistics showing that people with frontal lobe lesions commit violent crimes only 10 percent more frequently than the rest of us. From this he concludes that even permanent damage to the brain’s executive function should not count as a mitigating condition. But the concept of diminished responsibility is almost as much a pillar of the Anglo-American legal system as responsibility itself, and its actual erosion—as in the tabloid-stoked trend in Britain of trying minors as adults—is at least as troubling as its still-theoretical extension to all of us. Agreed, brain scans are probably not the right tools for establishing diminished responsibility, but the concept has been refined by witnesses, judges and juries ever since naturalistic accounts of mental illness began to gain traction, and it seems fairly robust as an intuition about justice.

The problem may be that Gazzaniga is using the wrong tools for the job. His work on split-brain patients obeys the basic logic of the “experimental lesion”—destroy an area of the brain, see what the animal is now unable to do, and infer the function of that area based on this new deficit. This may be a sound basis for making preliminary inferences about brain function, but it’s a shaky foundation on which to build a whole philosophical edifice. The fact that the workings of the Interpreter are most clearly revealed through an extreme pathology (severing of the corpus callosum) combined with a strenuously artificial experimental setup (show things to one hemisphere at a time) may be what gives the whole proposal its cynical cast. (Complicating matters is the infinite regress involved in interpreting the Interpreter’s interpretations, an issue that Gazzaniga passes over.) Under these conditions, the Interpreter module comes across as a self-congratulatory fabulist devoted to propping up our species’ self-esteem with the fiction of the soul’s freedom.

But if we shift the emphasis away from pathology, the pieces fall into a different pattern. Take the example from Gazzaniga’s neurologically intact childhood. He suggests that “I thought I saw a snake” is the Interpreter at work, misrepresenting reflex action as rational choice. It seems to me that it’s actually rather good shorthand for “At the perceptual stimulus of a rustle in the grass, my nervous system, primed by millenniums of natural selection to avoid serpentine hazards, sent a message via my amygdala to my legs instructing them to jump out of the way.” What is remarkable about the Interpreter is how well it works most of the time. We compulsively make patterns out of the available data, some of which are specious, but we also have self-correcting abilities, and the capacity to develop new layers of self-awareness. Philosophers tend to overestimate the part that rationality plays in human affairs, but neuroscientists seem to suffer from the opposite tendency. How is it that Gazzaniga, whose entire career has been based on the application of the scientific method, has so little regard for the workings of reason? With this denial he seems to claim rationality for himself and his fellow neuroscientists while consigning the rest of us to automaton status.

* * *

Now take the famous experiment purporting to show that voluntary choice is no such thing. The task that the participants were asked to perform was to move the hand and wrist. The subjects were encouraged to relax in a lounge chair and let their minds wander, moving only when they felt like it. With each subject wired to an EEG to detect activity in the area of the motor cortex that instructs the hand to move, the moment when the brain was ready to go with the action was recorded. The participants were also asked to note the time at which they were conscious of making the decision to move the hand. From the finding that conscious awareness happened crucial milliseconds after the brain was primed, the post-hoc nature of all our choices was supposedly confirmed. The precise nature of the task—its meaninglessness, capriciousness and whimsicality—was designed to represent “an incontrovertible and ideal example of a fully endogenous and ‘freely voluntary’ act.” If this existential languor is experimental psychology’s highest ideal of freedom, it’s clear why Gazzaniga has contempt for the concept. Anyone who has idly wondered when and how they will generate the momentum to get out of bed on a Sunday morning will recognize this as freedom of a pleasant but peculiar sort, in which the promptings of the body—a wiggling of the toes, a yawn, a stretch—often discernibly precede the directives of the intellect.

Contrast this feline ideal of liberty with the humanist notion of self-determination implicit in the consent forms that the experimental subjects doubtless had to sign. Informed consent rests on the same assumptions about the relationship between freedom and reason that ground our notions of diminished responsibility. The exercise of such freedom is not anarchic, whimsical or capricious; it is a highly structured intellectual activity, and there is a threshold of ability below which people, such as 12-year-olds, should not be held fully responsible for their actions or their signatures. Gazzaniga does make the connection between reason, freedom and responsibility, but all he does with it is wag an admonishing finger: “Criminals can follow the rules,” he lectures sternly in his one-paragraph conclusion. “They don’t commit their crimes in front of policemen. They are able to inhibit their actions when the cop walks by. They have made a choice based on their experience. This is what makes us responsible agents, or not.” For him, either you’ve got reason or you haven’t (and if you’ve got it, by God, you’re going down). The legal notion of diminished responsibility, by contrast, recognizes that moral thinking—the ability to see things from the perspective of others and then be constrained or not by this insight—is a more mature skill than the toddler’s ability to figure out how to get what he wants. The line the law draws between competency and incompetency can never be definitive, but isn’t it better to have an approximation of a standard than no standard at all?

One thing Gazzaniga stresses repeatedly is how ineradicable the notion of free will is. However much philosophers and scientists may pontificate about its nonexistence, he argues, even the most die-hard determinist cannot go about her business in the world without it. But this breezy confidence is somewhat undermined by his account of a fascinating recent experiment. Two groups of students were asked to play a game that had built into it the potential to cheat. As they waited to play, subjects were given some reading material consisting of excerpts from a text denying free will. For those of us who labor under the long neo-eugenic shadow of Francis Crick, it is delicious to learn that the passages came from Astonishing Hypothesis, Crick’s dogmatically scientistic account of the human mind/brain relationship. The subjects were divided into two groups. One was given a passage expressing Crick’s strong views on the illusory nature of freedom; the other read a paragraph that was neutral with regard to the question. The group primed by the determinist sentiments cheated on the tests at significantly higher rates than the control group. Who’s in Charge? comes tantalizingly close to transcending the lowering effects of neuroscientific determinism, but it is thwarted at the final fence by the author’s preoccupation with damaged brains at the expense of such effective instruments as his own finely tuned cerebrum.

  • Share
  • Decrease text size Increase text size

Before commenting, please read our Community Guidelines.