单选题 .  What if we could read the mind of a terrorist? Researchers at Northwestern University in Chicago say they have taken a step closer to that reality with a test that could uncover evil plans by measuring brain waves.
    In a study published in the journal Psychophysiology, psychologists John Meixner and Peter Rosenfeld used electrodes (电极) to measure the brain waves of 29 undergraduates who had been told to mock-plan either a terrorist bombing in Houston in July, or a vacation in a different city in a different month. The researchers then presented the students with the names of various cities, methods of terrorist attack and dates. As they did so, they scanned the subjects' brains. They watched for a particular brainwave—dubbed the P300, because it fires every 300 milliseconds—which signals recognition of something familiar.
    "The P300's amplitude (振幅) is very large when you see an object that is rare and personally meaningful to you," Meixner says. "So the amplitude of P300 was large when we presented the word 'Houston', the city where the attack was planned. In total we were able to identify 10 out of 12 'terrorists'". The investigators also correctly matched 20 out of 30 crime-related details, such as types of explosives and specific sites and dates.
    The P300's potential as a method for confirming concealed information was first recognized in the 1980s. But while it has long been touted as a possible substitute for the polygraph test, it has yet not been used by law enforcement anywhere in the world. One of the reasons is that it becomes difficult to use if investigators do not know the information they are trying to confirm. For instance, in Meixner and Rosenfeld's study, the researchers would have struggled had they not known that the city in which the attack was planned was Houston, since it would be only by luck or guesswork they would have included it in the sample list of names.
    What's more, the P300 is vulnerable to what scientists call "confounding factors". For instance, if the mock-terrorists in the study were raised in Houston, which was also the location of the attack, the researchers would not know for sure what was causing the P300 spike.
    But Meixner and Rosenfeld say that despite these shortfalls, the technology holds more potential than the polygraph. The polygraph measures responses like respiration and sweating, which can certainly be triggered by a lie, but can also result from any high-stress situation—including the mere experience of being interrogated by a police officer. While there is nothing that can correct this problem with polygraphs, P300s can at least be made more accurate by increasing the number of details you show a suspect.1.  What can we learn about the P300 from the research by John Meixner and Peter Rosenfeld?______