Brett Kavanaugh’s accuser, Christine Blasey Ford, passed a polygraph test before she came forward with her claim that he’d sexually assaulted her. This was, admittedly, to solidify her credibility in anticipation of intense scrutiny given the political stakes of a Supreme Court confirmation. And, what now feels like a decade ago—it’s been less than two weeks—Senator Rand Paul proposed President Trump polygraph every member of his staff to find out who had authored an anonymous New York Times op-ed as a double agent operating right under his nose.
The polygraph is simple machine. It’s a heart-rate monitor that charts subjects’ blood-pressure and perspiration during interviews or testimonies, purportedly to test his or her truthfulness: the faster your pulse flutters, for instance, the more nervous you are—and the more nervous you are, the more likely you are to be telling a lie. But the polygraph has no reliable backing in science, as partisans have leapt to point out in these last few weeks. It’s not a lie-detector test.
And yet, as its critics have amply cataloged, the culture at large—and the federal government in particular—still regards it with an outsized reverence.
Though there’s no technologically or scientifically satisfying explanation for our continued faith in the polygraph, there is a human explanation. “Truth technology,” as historian and polygraph expert John Philip Baesler calls it, is an imperfect science in part because the line between truth and falsehood is always going to be a little fuzzy. Baesler recently published a history of the polygraph, Clearer Than Truth, that traces the machine’s legacy from its technical origins in the 1920s to its widespread and authoritative use by federal government after World War II.
A congressional review in the 1980s panned the polygraph, and then in the early 2000s the National Academy of Sciences determined that, as Baesler put it in a recent interview, “the reliability of a lie detector test may vary depending on the skills of the interrogator and the specific situation about which somebody is being questioned. But,” he went on, “the basic problem of the lie detector is that it wants to infer causes from consequences.” A quickening pulse, for instance, is a consequence—but how can we be sure of its cause? As the interrogator, “You’ll have to make an inference that it is fear of being caught lying rather than just being embarrassed by the nature of the situation, or having a bad conscience for personal reasons that you’re not even aware of. You’re forced to make this gigantic leap in logic independent of the technology, of how precise you are or how precise the machine is. That leap in logic never goes away.”
And at the heart of the questions that Baesler’s book attempts to answer— “What exactly did the polygraph measure? How does a machine measure imponderables such as loyalty to democratic values?”—is a problem so fundamentally human it can only ever elude us. The impossibility of a perfectly pure truth to satisfy every perspective is also a big part of why the polygraph, despite its proven inaccuracy, crops up so much in politics, Baesler said.
It’s a useful tool for telegraphing truthfulness. “Obviously in politics, people want to look good in public, or they don’t want to take the blame,” he said. “So if they’re attempting to be able to point to something specific and say, See, I can prove to you that I was not the leaker! the idea of the ‘lie detector’ is more powerful”—more powerful, that is, than the reality that the actual polygraph is far from infallible.
The power and the mystique of the polygraph come from its presence in cop shows—and its continued use by the federal government. “The authority of the polygraph comes indeed from the authority of an organization like the CIA,” Baesler said, where its main purpose is also to send a message about power. “It gives them a little bit of a cutting edge, it betrays the sense of the elite: that you’ve made it, you’re part of the insiders’ club if you went through that ordeal,” he adds, describing a potent ritual. “The medical instruments that they’re using have been around since the 19th century. They were just reappropriated, so it is very old school but on the other hand that also gives it a certain cache.”
When we perpetuate that mystique, however, we also permit its misappropriation. Here, Baesler described another contemporary example. “When somebody voluntarily takes a lie detector test, what they do is they take it in private,” he said. “If it gets you the results you want, you publicize the fact that you just passed the ‘lie detector test.’ And if you did not get the result you want, you just stay quiet about it.” Either way, the truth—whatever that is—is on your side.
