Cops Buy Voice Stress Analyzers; Experts Dubious


Police say that a lie detector that looks for vocal tremors in recorded conversations is eliciting confessions, reports the St. Louis Post-Dispatch. Many scientists, including Washington University psychologist Mitchell Sommers, say the voice analysis devices are little more than $10,000 wastes of money. In distinguishing liars from truth-tellers, flipping a coin works better, he says a study showed. “It’s beyond my imagination why anyone would buy one of these devices,” Sommers said.

Yet at least 1,400 law enforcement agencies have purchased a Computer Voice Stress Analyzer from the National Institute for Truth Verification, a Florida company that pioneered so-called voice stress analysis. Voice analysis assumes that lying causes stress, which in turn causes tiny telltale tremors and other modulations in a person’s voice. Sommers says the devices are pretty good at detecting stress. But whether that stress indicates lying is another question. There’s the stress associated with lying and there’s also the stress of being an innocent person in an interrogation room. University of Chicago psychologist John Cacioppo says the devices depend on consistent reactions, when individuals can have different physical responses to lying. He adds: “We tend to treat lies as if they are all the same. There’s a spontaneous lie, well-rehearsed lie, a lie for greater good, a lie for individual gain.”


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