Psychologists have long known how hard it is to spot a liar. In 2003, psychologist Bella DePaulo, now affiliated with the University of California at Santa Barbara, and her colleagues combed through the scientific literature, gathering 116 experiments that compared people’s behavior when lying and when telling the truth. The studies assessed more than 100 possible nonverbal cues, including averted gaze, blinking, talking louder (a nonverbal cue because it doesn’t depend on the words used), shrugging, shifting posture, and movements of the head, hands, arms, or legs. None proved reliable indicators of a liar, though a few were weakly correlated, such as dilated pupils and a tiny increase—undetectable to the human ear—in the pitch of the voice.
Three years later, DePaulo and psychologist Charles Bond of Texas Christian University reviewed 206 studies involving a total of 24,483 observers judging the veracity of 6,651 communications by 4,435 individuals. Neither law-enforcement experts nor student volunteers were able to pick true from false statements better than 54 percent of the time—just slightly above chance. In individual experiments, accuracy ranged from 31 to 73 percent, with the smaller studies varying more widely. “The impact of luck is apparent in small studies,” says Bond. “In studies of sufficient size, luck evens out.”
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This size effect suggests that the greater accuracy reported in some of the experiments may just boil down to chance, says psychologist and applied-data analyst Timothy Luke at the University of Gothenburg in Sweden. “If we haven’t found large effects by now,” he says, “it’s probably because they don’t exist.”
Police experts, however, have frequently made a different argument: that the experiments weren’t realistic enough. After all, they say, volunteers—mostly students—instructed to lie or tell the truth in psychology labs don’t face the same consequences as criminal suspects in the interrogation room or on the witness stand. “The ‘guilty’ people had nothing at stake,” says Joseph Buckley, president of John E. Reid and Associates, which trains thousands of law-enforcement officers each year in behavior-based lie detection. “It wasn’t real, consequential motivation.”
Samantha Mann, a psychologist at the University of Portsmouth in the U.K., thought that such criticism by police had a point when she was drawn to deception research 20 years ago. To delve into the issue, she and colleague Aldert Vrij first went through hours of videotaped police interviews of a convicted killer and picked out three known truths and three known lies. Then Mann asked 65 English police officers to view the six statements and judge which were true and which were false. Since the interviews were in Dutch, the officers judged entirely on the basis of nonverbal cues.
The officers were correct about 64 percent of the time—better than chance, but still not very accurate, she says. The officers who did worst were those who said they relied on nonverbal stereotypes like “liars look away” or “liars fidget.” In fact, the killer maintained eye contact and didn’t fidget while deceiving. “This guy was clearly very nervous, no doubt,” Mann says—but he controlled his behavior to strategically counter the stereotypes.
from Hacker News https://ift.tt/3crnBpF
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