doc_text: A lie detector that measures brain waves would be more accurate than polygraphs, which measure bodily functions, says its developer.
  "It would probably not falsely accuse any innocent people, and it would probably pick up 70 to 90 percent of guilty people," says J. Peter Rosenfeld, a Northwestern University professor of psychology and of neurobiology and physiology.
  "I think that's better than existing units."
  The American Medical Association and the congressional Office of Technology Assessment have said polygraphs are wrong 15 percent to 50 percent of the time.
  Rosenfeld's lie detector picks up brain-wave activity through electrodes attached to the scalp, amplifying the signals and feeding them into a computer, which coordinates the information and displays it on a video screen.
  "If sensory information has a special meaning for you ... then your brain will respond with a special kind of trough called the P3 wave," he said.
  In tests at Northwestern, subjects have been asked to look at a series of words, most with no special meaning.
  "Occasionally, they'll see a word that is meaningful, like some anti-social act they're involved in _ cheating on tests or using drugs _ which is sometimes the case here," Rosenfeld said.
  "When they see terms like that, their brain waves break into P3 waves."
  Polygraphs measure the physical expression of emotions _
  pulse, sweating, blood pressure and breathing, he said.
  Advertising researchers have measured P3 waves to better gauge what consumers want instead of what they say they want, and psychiatrists can detect certain disorders, such as attention deficits, by measuring them, he said.
  Rosenfeld has worked on the detector for almost four years and says it could be widely used within three more.
  He published a study last year and will publish another this summer in the International Journal of Neuroscience.
  "It's a perfectly valid way of detecting lies," said Sidney Weinstein, a professor of neurology at New York University College of Medicine in New York City and editor of the Danbury, Conn.-based neuroscience journal.
  However, a brain-wave lie detector would probably cost 10 times as much as the $500 to $600 for a polygraph, and the operator would need a great deal more training, Weinstein said.
summary_text: The American Medical Association and the Congressional Office of Technology Assessment have said that polygraphs give a false report as often as 50 percent of the time.
  A professor of psychology and neurobiology is developing a lie detector that measures brain waves, rather than bodily functions, as do the polygraphs now in use.
  He claims that it will pick up 70 to 90 percent of those lying, and will falsely accuse no one.
  The developer also said that the new detector will be on the market in four years, and it will cost ten times as much as the polygraph machines now in use.