The lie detector (aka #polygraph) is back in the news. The name polygraph is based on the fact that the device can record and display several things at once. Like a dashboard.
In the 1920s, a young American physiologist named John Larson devised a version for detecting liars, which measured blood pressure, respiration, pulse rate and skin conductivity. Larson called his invention, which he took with him to the police, acardiopneumo psychogram, butpolygraphlater became the standard term. To this day, there is no reliable evidence that polygraphs actually work, but the great British public will no doubt be reassured by official PR that makes our masters sound like the heroes of an FBI crime series.
Over a hundred years ago, G.K. Chesteron wrote a short story exposing the fallacy of relying on such a machine. Even if the measurements are accurate, they can easily be misinterpreted.
There’s a disadvantage in a stick pointing straight. The other end of the stick always points the opposite way. It depends whether you get hold of the stick by the right end.
There are of course many ways in which the data displayed on the dashboard can be wrong – from incorrect and incomplete data to muddled or misleading calculations. But even if we discount these errors, there may be many ways in which the user of the dashboard can get the wrong end of the stick.
As I’ve pointed out before, along with the illusion that what the data tells you is true, there are two further illusions: that what the data tells you is important, and that what the data doesn’t tell you is not important.
No machine can lie, nor can it tell the truth.
G.K. Chesterton, The Mistake of the Machine (1914)
Hannah Devlin, Polygraph’s revival may be about truth rather than lies (The Guardian, 21 January 2020)
Megan Garber, The Lie Detector in the Age of Alternative Facts (Atlantic, 29 March 2018)
Stephen Poole, Is the word ‘polygraph’ hiding a bare-faced lie? (The Guardian, 23 January 2020)