The subjects were asked to perform a simple task: hit a button as soon as they recognized a word flashed on a computer screen. While monitoring the subjects' brain waves, the researchers alternated nonsensical strings of letters with neutral words such as "table," and emotionally evocative words like "maggot" and "cancer." What they found was that normal subjects spent more time processing emotion-laden words than the psychopaths. "When you see a word like 'cancer,' you have all sorts of associations - fear, or you think of someone who's had cancer," says Hare. "But for psychopaths, the word 'cancer' and the word 'table' had the same emotional connotations - which is to say, not very many. It's as if they're emotionally color-blind."
Even more staggering were the findings of a study conducted by New York City psychiatrist Joanne Intrator, with Hare's collaboration, at the Bronx Veterans Administration hospital in 1993. The investigators employed the same language test, this time injecting the subjects with a radioactive tracer and scanning color images of their brains. As normal subjects processed the emotion-laden words, their brains lit up with activity, particularly in the areas around the ventromedial frontal cortex and amygdala. The former plays a crucial role in controlling impulses and long-term planning, while the amygdala is often described as "the seat of emotion." But in the psychopaths, those parts of the brain appeared to remain inactive while processing the emotion-laden words. That, says Hare, helps explain why a psychopath's conscience is only half-formed. "I showed the scans to several neurologists," recalls Hare. "They said that it did not even look like a human brain. One of them asked, 'Is this person from Mars?' "
Hare's next experiment will be even more sophisticated. Slated to begin at the University of British Columbia in May, it will be run by graduate students Andra Smith and Kent Kiehl. (The latter happened to grow up three blocks from serial killer Ted Bundy's home in Tacoma, Wash., which prompted Kiehl to take up his line of study.) The researchers plan to apply the same linguistic test to 32 subjects, half of whom are psychopaths housed in a maximum-security federal prison near Vancouver. Most of those volunteers, who will be transported in shackles under armed guard, have committed violent crimes, including rapes and murders.
Hare says that the study - which was turned down for funding by the federal Medical Research Council last year, and is now privately supported by the B.C. Medical Services Foundation - will provide a better picture of what is going on inside a psychopath's brain. The reason: it will take advantage of the university's 18-month-old, state-of-the-art General Electric magnetic resonance imaging (MRI) facility - and the expertise of its scientists, radiologist Bruce Forster and physicist Alex MacKay. The unit itself, visible through a window from a control room, is a small white room equipped with a gurney that slides along a horizontal track into a short tunnel. That is where subjects lie as the machine probes their brains with magnetic torque. When Hare and his colleagues tested the procedure on a psychopathic subject last fall, the convict viewed the computer prompts through mirrors aimed at a rear-projected screen. And because the MRI is thrown off by any metal in its vicinity, the subject had to respond by pressing a touch-pad connected to a computer by fibre optics instead of a keyboard or joy stick wired with metallic cable. Capturing brain images at the rate of one every 40 milliseconds or so, the experiment effectively creates a video of the psychopath's brain as it processes emotional information.
