WHILE BRAIN IMAGING OFFERS NEW KNOWLEDGE, IT CAN BE AN ILLUSION

There, right there, see that spot of blazing red in a cool blue sea of your
cortex? That's your brain on drugs. Or, more specifically, that's the brain
of a recovering cocaine addict, clean for months, who sees a mound of white
powder. His brain responds with the same craving and anxiety -- marked by
the red on the brain scan -- as when he was snorting every night, which is
why addiction is so tenacious.

And here, see how a chess grandmaster activates the region of the brain
that stores memories, such as those of games he has played or studied? But
in the brain of a neophyte the activity is over here, in a region that
analyzes positions from scratch.

If you're impressed, you're not alone. Brain scans such as these have a
power to persuade that other forms of data lack. Although measurements of
recovering addicts' heart rates and skin properties (perspiration,
basically) had already shown that seeing cocaine triggers an intense
physiological reaction, and although grandmasters can tell you they
memorize old game positions and strategies, in both cases the brain scans
carried the day. They convinced policy makers that addiction reflects
biology (rather than a character flaw), and laypeople that experts think
differently from novices.

Blame it on the cognitive paparazzi. Neuroimaging such as PET and fMRI are
seducing laypeople and scientists alike into believing we know more than we
do about how and why we think, feel and behave, some scientists say. The
power of brain imaging, says Frank Keil, a Yale University psychology
professor, reflects "the illusion of explanatory depth. If people see
something, they are often deluded into thinking they understand it better
than they really do."

That is especially so now that neuroimaging is expanding beyond "where does
the brain do multiplication?" to complex social and moral behaviors. In a
fit of physics envy, researchers in economics, political science and even
philosophy are deciding that neuroimaging is just the thing to make them
more scientific. Yet the results are less than groundbreaking.

Social psychologists had shown that people hold both implicit and explicit
attitudes about other races, for instance, attitudes that are often at
odds, says Elizabeth Phelps of New York University. Then along came fMRI
images showing that unconscious brain activity, in the anxiety-generating
amygdala, indeed increases when people see the face of someone of a
different race.

"When we got the pictures that tied this to a neural system, it didn't
advance the science of social attitudes all that much," she says. "But if
you're saying something based on a brain scan, people believe it a lot more
than when social psychologists say the same thing based on behavioral data."

So it goes in political science, too. "If a study finds that the 'anger'
part of the brain lights up when a Democrat watches a Republican ad more
than when he watches a Democratic ad, have we learned anything?" asks Prof.
Keil.

Not scientifically. But with every such study, the public gets a new, and
troubling, message. "The more we publish these things, the stronger the
message that there is a brain excuse for everything," says Prof. Phelps.
"That makes many people say it's beyond their control, when in fact just
because it's in the brain doesn't mean it's any less controllable."

Another danger of being seduced by the cognitive paparazzi is that pretty
pictures showing where in the brain something occurs obscure the fact that
"where" is usually less interesting and important than "how" or "why." For
instance, psychotherapists have reported that therapy lifts patients'
depression, or alleviates obsessive-compulsive disorder. Those claims were
often dismissed as unscientific -- until brain images showed that activity
in regions linked to those illnesses really did change following successful
therapy. The discovery was hailed as explaining how psychotherapy works.
But did it?

"It doesn't answer the important question of how successful treatment
changed brain activity," says Susan Fitzpatrick, vice president of the
James S. McDonnell Foundation, which funds neuroscience. She helped
organize a forum on neuroimaging last month for the American Association
for the Advancement of Science.

Sometimes, to be sure, finding "where" solves a longstanding mystery. These
have been among neuroimaging's greatest hits. For instance, brain scans
show that when people conjure up a mental image (picture a giraffe), the
same neuronal apparatus in the visual circuits becomes active as when you
see a giraffe in the flesh. There had long been a debate over whether
seeing in the mind's eye is really seeing; it is. Neuroimaging also shows
that memory isn't a single process centered in one brain structure, as was
long believed. Instead, different regions form and retrieve different kinds
of memories.

For all its flaws, neuroimaging is here to stay. No self-respecting psych
department can afford to forgo it. Of the dozen or so new faculty members
recently hired by his department, says Phillip Shaver, chairman of
psychology at the University of California, Davis, 10 use primarily
neuroimaging. Economists, political scientists and sociologists are not far
behind. As with all powerful tools, let the user beware.