Is There Room for the Soul?
New challenges to our most cherished beliefs about self and the human spirit
But something curious happened within a generation of that book's publication. Psychology quite suddenly dropped the investigation of consciousness. Dissatisfied with the reliance on introspection-how do you make an objective science out of people's subjective reports on their private experiences?-psychologists followed the lead of researchers like Ivan Pavlov and John Watson and turned to the observable results of consciousness: behavior. Or at least most did. For those less enchanted by the business of running rats through mazes there was the siren song of Sigmund Freud's theory of the unconscious mind. For more than half a century, varieties of behaviorism and psychoanalytic theory dominated the field of psychology, banishing the subject of consciousness to the realm of the occult or mere philosophy.
Slowly, however, developments conspired to bring the banished subject back. The invention of program-controlled computers in the 1940s gave birth to artificial intelligence, a branch of computer science dedicated to building machines to accomplish tasks requiring intelligent behavior. At the same time, the effort to create artificial intelligence encouraged a whole new field of psychology concerned with finding universal principles for different mental processes: cognitive psychology.
Also crucial to the rise of the scientific study of consciousness was the very sort of technology so frustratingly unavailable to earlier neuroscientists (including the young Freud), technology that could show what the brain was actually doing when someone experienced the color red or remembered a phone number. A raft of new brain-imaging and scanning technologies, including computed tomography (CT) scans and positron emission tomography (PET) scans, magnetic resonance imaging (MRI) and functional magnetic resonance imaging (fMRI), and magnetoencephalography (MEG), came to fill this need. These instruments enabled researchers to observe brain structure and activity in a variety of noninvasive ways, while the newest gadget in the arsenal, transcranial magnetic stimulation (TMS), actually allows the researcher to disrupt activity in the cortex underlying specific mental tasks. Well before such devices were available, however, in the late 1940s, a Canadian psychologist named Donald Hebb put forth a remarkably resilient hypothesis. According to Hebb, groups of neurons that fire together tend to form what he called "cell-assemblies," the activities of which persist even after the event that triggered their firing is no longer present. These assemblies, in effect, come to represent the triggering event. The neurophysiological basis of thought, Hebb concluded, was the sequential activation of various groups of cell-assemblies.
Variants and refinements of this hypothesis, particularly the notion that neurons that fire together wire together, have been at the center of the research agendas of top cognitive neuroscientists during the past two decades. The most ambitious of these scientists-call them, if you will, the hard-core demystifiers-came to believe quite strongly that most of the mysteries of the mind, if not all of them, are reducible to the biochemical mechanisms underlying these neural networks. These scientists have been a formidable lot, including at least a couple of Nobel laureates who moved to the study of consciousness after doing major work in other fields. One of them, Gerald Edelman, winner of the 1972 prize for his work in immunology, is the founder and director of the Neurosciences Institute, which sits to the west of the Salk Institute on the same La Jolla mesa. Edelman launched the institute in 1981 as part of the Rockefeller Institute in New York City but brought it to La Jolla in 1993, where he also chairs the neurobiology department of the Scripps Research Institute, directly across the street from Neurosciences. A man as conversant with philosophy, literature, and music as he is with science-his early passion was the violin, but he feared he lacked the right stuff to perform-Edelman went into medicine, and then research. As he explains when we meet in his office, Darwin's theory of natural selection is what guided his groundbreaking research on antibody structures, and it is what underlies his theory of neuronal group selection in his work on consciousness. "I wanted to bring Darwin's selectional process to neurons," he says.
advertisement
