Nancy, an airline pilot, arrived promptly for a routine physical. She'd had exams before, but this time was different. She was asked to lie down and place her head in a large metallic torus, while a video screen flashed a series of images before her eyes—the inside of a 747 cockpit, a view of a target seen through a rifle's scope, a chemical formula for polyester, a photo of Bill Clinton. In an adjacent room, a technician watched as colorful images of Nancy's brain appeared on his computer screen, lighting up like brushfires with different hues in response to the pictures. As the test ended, the technician forwarded the results to Nancy's employer.
Reporting for work the next day, Nancy was confronted by her supervisor and an official from the U.S. Federal Aviation Administration. They informed her that the brain images showed Nancy might develop schizophrenia, and had a surprising familiarity with assault rifles as well. The agency revoked her pilot's license. The airline promptly fired her.
This scenario is fiction. But the basics of the technologies it alludes to already exist. New ways of imaging the human brain and new developments in microelectronics are providing unprecedented capabilities for monitoring the brain in real time and even for controlling brain function.
The technologies are novel, but some of the questions that they will raise are not. Electrical activity in the brain can reveal the contents of a person's memory. New imaging techniques might allow physicians to detect devastating diseases long before those diseases become clinically apparent. And researchers may one day find brain activity that correlates with behavior patterns such as tendencies toward alcoholism, aggression, pedophilia, or racism. But how reliable will the information be, how should it be used, and what will it do to our notion of privacy?
Meanwhile, microelectronics is making access to the brain a two-way street. The same electrical stimulation technologies that allow some deaf people to hear could be fashioned to control behavior as well. What are the appropriate limits to the use of this technology? In an age of overcrowded prisons, might society be tempted to release criminals if behavior-modifying brain implants could guarantee that they would pose no further threat?
Truth and consequences
Coupled with powerful microelectronics, science's understanding of the brain is opening the door to new ways of handling criminal investigations and screening potential employees. Several recent applications involve variants of the "guilty knowledge" test, in which investigators try to determine the presence or absence of specific memories implying a person's guilt by recording electric signals from the head.
So-called brain fingerprinting is the most striking of these. Lawrence A. Farwell [photo, right], chairman and chief scientist of Brain Fingerprinting Laboratories Inc. (Fairfield, Iowa), a commercial venture, invented the technique. Farwell claims that brain fingerprinting allows investigators to "detect information stored in the human brain" for use in forensic examinations. He promotes the method for evaluating criminal suspects and screening for terrorists.
The system that performs brain fingerprinting resembles an electroencephalogram (EEG) under computer control. In a test, the subject is seated in front of a computer screen, wearing a headband with EEG sensors. A series of words, sounds, or images is presented. Some of these are called "irrelevants": words or images unrelated to the crime or to the investigation. Irrelevants establish a baseline of activity for unimportant information.
Others are "target" stimuli: phrases or images that the subject has been told to pay particular attention to. Targets act as a baseline for information noteworthy to the subject. Finally, there are "probes": details of the crime under investigation that an innocent would have no knowledge of, such as a picture of a sofa on which a murder victim's body was found.
In response to these cues, microvolt electrical signals that correspond to brain activity, known as event-related potentials (ERPs), can be measured on the scalp at times ranging from a few tenths of a second to about a full second after the cue. Distinctive ERPs occur when a subject reacts strongly to a meaningful event. For example, a murderer might respond to the probe photograph of the sofa.
Such a reaction would result in a special ERP that includes the so-called P-300 wave. P-300 is a well-researched response that begins 300 ms after the photo appears and is thought to correspond to the brain's recognizing a noteworthy bit of information. By comparing the ERPs from probes, targets, and irrelevants using a computer algorithm, Farwell claims the system can determine whether the probes represent information that is known to the subject—guilty knowledge [see image].
Brain fingerprinting may seem similar to a polygraph (usually called a lie detector), but it differs in important ways. A polygraph measures physiologic responses such as heart rate, sweating, breathing, and other processes that are only indirectly related to brain function. Brain fingerprinting's information comes directly from brain function. It and other related tests do not measure truthfulness, but seek to determine whether the subject has a particular memory.
Already brain fingerprinting has been used in two criminal investigations. One was an attempt to win a new trial for Terry Harrington, imprisoned in Iowa for 22 years for murder. Farwell claims that his test shows that Harrington did not commit the crime. A second case involved a man accused of rape and murder in Missouri. Shortly after being found guilty by brain fingerprinting, the suspect (who volunteered to take the test) confessed.