Liar Liar Pants on Fire

Langleben's research is noteworthy because it demonstrated that it's possible to see the physical differences between lying and truth telling within the brain. But though Langleben's work pinpointed a few locations that are active during deception, he and scientists involved in similar studies caution that lying is a complex behavior, and that it's likely to be linked to a large number of brain sites, many of which remain unknown.


Harvard's Kosslyn hopes to make some inroads on this problem by charting the brain activity corresponding to disparate types of lies. Broadly speaking, Kosslyn suspects that the location of a deception within the brain and the amount of energy needed to carry the deception out are determined by whether someone is telling a premeditated lie or on-the-spot fib. To test this idea, Kosslyn's team told volunteers to take an actual memory and warp it into a lie. One person could, for instance, imagine that as a high school baseball player he hit 50 home runs when in reality he was a benchwarmer. Later, during an fMRI scan, the volunteers were asked questions and instructed to either stick to the memorized lie, tell the truth, or make up something new on the spot. So far, based on just a smattering of initial results, Kosslyn says that fMRI scans appear to distinguish between these different types of lies. Spontaneous lies seem to activate parts of the frontal lobes that play a crucial role in what's known as working memory-short-term, immediately relevant information-whereas memorized lies don't appear to affect this part of the brain. "We hope that in fact there will be unique brain signatures for the different types of lies," Kosslyn says.


Even if fMRI research proves fruitful, the equipment isn't likely to attain widespread use for lie detection. The machines are bulky, expensive (to buy and to operate), and highly sensitive to motion. "Just twitch a little bit, and it'll ruin the scan," says Kosslyn. Some researchers, however, are experimenting with another brain-scanning tool that may turn out to be more practical than fMRI: the electroencephalograph (EEG), which directly measures the electrical output of the brain rather than inferring brain activity from blood flow, as the fMRI does. EEGs are relatively cheap, portable, and unobtrusive.


In one EEG study, University of South Carolina researcher Jennifer Vendemia had student volunteers don a cap fitted with 128 electrodes that record brain waves. The students were then asked to look at a computer screen on which was displayed first a simple sentence that was obviously true or false-"The grass is green," for example, or "Mickey Mouse shot Abraham Lincoln"-followed by a question: either "True?" or "False?" The volunteers were told to respond by telling the truth sometimes and lying at other times. In another experiment, Vendemia had the students commit a mock crime, in which they raided the office of a make-believe professor and stole a copy of an upcoming exam.