The Zombie Within

Today’s volunteer is Jim, a tall, dark-eyed sophomore. Once he’s wired — electrodes on the right hand, sensors on the left hand — Carter proceeds to determine the appropriate level of electrical bite. “You want it to be the maximum level of discomfort that the subject can tolerate without it being painful,” he deadpans. For reasons that are not understood, people have wildly different responses to the shocks. The head of Caltech’s Human Safety Committee “maxed out” the machine, Carter tells me — even at full charge, the shocks didn’t bother him at all. I tanked a mere third of the way up the scale. Jim settles on a point around the two-thirds mark. Now he is asked to rest his head in a stand so that Carter can track the motion of his eyes. In all, he’ll be monitored by three computers, though with the electrodes dangling from his arms and the metal contraption cradling his head, the whole setup looks as if it’s been devised by Victor Frankenstein.

Jim is now ready to begin. Soon elephants and butterflies are flashing across the screen. Halfway through the test, it’s clear his unconscious is learning its stuff — the skin-conductance peaks are beginning to appear before the shocks hit, which means that somewhere in his mind neurons have learned when to expect these jolts. This is a brand-new experiment, Carter tells me. They get to study both “trace” and “delay” conditioning at once, giving them an unprecedented window into some of the unconscious mechanisms of perception.

Yet if Koch’s team is beginning to reveal the physiological footprints of our most intimate mental state, the question remains: How do the material processes they are discovering give rise to subjective states of mind? How is it that neuronal spiking in response to, say, the color red gives rise to the rich subjective experience of “seeing” red, the full-on panoply of feeling that philosophers refer to as qualia — the redness of red, the painfulness of pain and so on? For all our advances in neuroscience, Oliver Sacks wrote in a recent essay, “Neuronal activity and psychic activity still seem utterly different,” even “incommensurable” in kind.

In their Nature article, Crick and Koch frankly admit their ignorance: “No one has produced any plausible explanation of how the experience of the redness of red could arise from the actions of the brain,” they write. In short, the mind-body problem remains as intractable as ever. Crick and Koch’s innovation has been to sidestep the grand philosophical dilemma — what Chalmers calls the “hard problem” — and to get on with the mundane field work. Rather than try to explain how consciousness arises, or even what consciousness is, they have confined themselves to identifying the neurological conditions under which consciousness is present.

Koch draws a parallel with the discovery of the double helix and the subsequent development of gene science. In the early 1950s, he points out, “No one had much idea what a gene was,” but the discovery of the physical structure of DNA provided a foundation on which to investigate the question. Half a century later, geneticists have cataloged most of the human genome; they can insert, delete and alter individual genes at will. Just as an understanding of the physical basis of heredity revolutionized our view of life, so, Crick and Koch believe, understanding the material processes behind consciousness will lead eventually to a comprehensive and applicable theory of mind.

5. RETURN OF THE ZOMBIES

“I know of no logical reason why you couldn’t be a zombie,” Koch declares amiably as we chat one morning in the Caltech cafeteria. Considering my insomnia the night before, I must admit to feeling less than fully present. Koch, however, is jazzed as ever and about to embark on another “awesome” climbing trip to Zion National Monument, where he and Zinn will rappel down a 1,500-foot canyon, at times having to travel from one drop to the next underwater. In addition to a heavy load of climbing tackle, they’ll be hauling wetsuits. Whatever doubts I harbor about myself, I am pretty certain that anyone who can think through such an operation is unlikely to be a zombie. The idea of planning is in fact central to Crick and Koch’s thesis about the purpose of consciousness.

In principle, Koch says, there is no reason why consciousness is necessary to life. With enough “input sensors and output effectors,” it is conceivable that “A zombie could pretty much do anything.” But since every zombie behavior must be hard-wired, the more situations it must respond to, the more complex its internal mechanism must become. Instead, “Evolution has chosen a different path, synthesizing a much more powerful and flexible system” that we call “consciousness.” The main function of this innovation, he and Crick propose, is to enable organisms to deal rapidly with unexpected events and to plan for the future. As Koch likes to say, consciousness puts us “online,” allowing us to override our instinctual “offline” programming.

Within Crick and Koch’s scheme, the neural correlates of consciousness map the things in an organism’s environment of which it is currently aware. As my awareness flits from, say, the cup of coffee in front of me to the sound of a bird singing outside, the contents of this “cache memory” change. Thus, Crick and Koch propose that consciousness is innately linked to short-term memory. That linkage is key, Koch says, for it suggests what he refers to as “an operationalized test” for consciousness. Since zombie agents operate purely according to preprogrammed rules, a zombie would have no need for short-term memory, and hence Koch believes the absence of this feature would serve as an indication that consciousness was also missing.