No one wants to hear that subliminal messages can make us ruder, more loving or plain prejudiced. Or that the brain sends signals to start moving muscles well before we "decide" to move them. Reducing emotion and memory to maps of synapses undermines our sense of self-control and makes free will seem illusory.

But if traditional neuroscience is disturbing, the really creepy stuff is on the horizon, reports neuroscientist Richard Restak in The Naked Brain. Marketers and politicians would like to literally get into our minds, using the results of brain scans and psychology experiments to alter perceptions of reality. They might use "backward framing" to mold people's memories. (In one experiment, 16 percent of adults remembered seeing Bugs Bunny at Disneyland, where, as a Warner Bros. Looney Tunes character, Bugs could never be.) Or a political party might take advantage of the fact that people trust candidates who resemble themselves. "It would not be all that complicated," Restak writes, "to send you a morphed picture of a political candidate incorporating elements from your own face drawn from, say, your driver's license photo." Each house, each voter, gets a slightly different contender.

Yet despite the hype on the book's dust jacket, Restak is more interested in summarizing science than in speculating how people might be manipulated by it. He rings alarms, but only occasionally; instead, he spends chapter after chapter recapping experiments and supplying newspaper-like quotes from experts. Taken individually, the experiments are fascinating, and Restak, who has written self-help books, encourages readers to try the simpler ones at home. But the constant jumping from one to the next makes The Naked Brain seem less written than pasted together. While the writing is clear, and Restak is sympathetic to how complicated the material can be for lay readers, there's too much information stacked too closely.

It's a shame because the philosophical discussions lurking in these pages never get the space they need. Take the scant eight pages he devotes to racial stereotyping. Restak suggests that readers visit a Web site where they are asked to sort images that pop onto the screen. First, they sort pictures of white and black people -- half to the left, half to the right. Next round, they do the same for positive and negative words such as "awful," "fantastic" or "lovely." Third, there's a combination round: Good words and pictures of black people are sorted to one side, white people and bad words to the other. Finally, uncomfortably, those pairings are reversed. Many people taking the quiz can sort more quickly and accurately when black and bad are coupled.

So they're bigots, right? Restak differs:

"According to this assumption, automatic responses reveal the 'real' you . . . with the follow-up response [i.e., battling the prejudice] entailing nothing more than an attempt to make nice. But when you think about it, why should those automatic responses over which we have no control be granted precedence over more thoughtful reactions, which reflect our consciously espoused beliefs and values?"

He cites the case of a black man married to a white woman who, in a moment of passion, called her husband a racial slur. The woman's frontal lobe -- which processes reason -- was overwhelmed with anger from a reptilian part of her brain. Restak would argue that it's the interplay of the automatic and thoughtful portions of her mind that determine her "true" personality, with weight given to the latter. The husband didn't see it that way. The marriage disintegrated.

But should it have? For one slip that she "deeply regretted"? Restak devotes just one paragraph to this conundrum. Other tantalizing debates that neuroscience could frame and focus -- Should introverts be allowed (or encouraged) to convert into extroverts by swallowing pills? Should employers screen applicants with MRIs? -- are relegated to the afterword.

But Restak's preference for proven science over speculation reveals another theme of The Naked Brain: Neuroscience has limits. The mind is too intricate for scientists to sort out from a brain scan who will drink Coke or Pepsi, much less to address deeper concerns. "The answers provided by neuroscience aren't necessarily definitive," he writes. "Indeed, they often aren't as valid as information gathered from traditional sources (asking questions, making behavioral observations, etc.)" Keeping limits in mind will be hard, however: Human brains are wired to want more than they have. ·

Sam Kean is a writer living in Washington, D.C.


How the Emerging Neurosociety Is Changing How We Live, Work, and Love

By Richard Restak

Harmony. 255 pp. $23