Truth Machines

When the first lie detectors appear at the beginning of the 20th century, many consider them as almost infallible machines capable of directly revealing human truth. Pulsations, breathing, and perspiration suddenly become measurable data. Modern justice then begins to dream of an entirely scientific interrogation freed from the ambiguities of language.

The first modern lie detectors appear in the United States in the 1920s. By recording at once heart rhythm, breathing, blood pressure, and perspiration, they rest on an intuition that seems revolutionary: the body would betray, despite itself, the stress of lying. Their promoters present the polygraph as a scientific instrument capable of surpassing the limits of human testimony.

This confidence embraces an era's obsession with objective measurement of behavior, where experimental psychology, criminology, and forensic medicine all dream of converting emotions into readable data. The machine also has an obvious spectacular force: with their suspects connected to cables and dials, photographs and public demonstrations give it the air of a futuristic medical apparatus.

Scientists however quickly spot the flaws, since fear or simple anxiety suffice to falsify the curves without any lie being involved. The polygraph has nevertheless retained its aura, because it embodies a very modern fantasy, that of a technology that would finally make thoughts perfectly transparent.