A new generation of lie detectors is being developed (see Prospect, Oct 09, Lie Detection by Ian Leslie, p66). Remember the scene in Meet the Parents when Robert De Niro wires up his future son-in-law in the basement and interrogates him. This was the old-fashioned polygraph, which works by monitoring stress levels – blood pressure, heart-rate, etc.
The new models work by scanning the brain. When we tell a lie, even if we keep the stress levels down, an extra burst of mental energy is required. This energy is released in the areas of the brain responsible for reasoning and self-control. So if the scanner suddenly spots us thinking hard and carefully as we answer a progression of simple yes or no questions, then we are probably lying.
It could be bunkum. Many neuroscientists question its effectiveness. And a woman in India who was convicted of murder on the basis of evidence from such a lie detection test had her case overturned because there was no material evidence connecting her to the crime.
Why is the thought of an infallible lie detector so unsettling? It’s not because we are all inveterate liars terrified of being exposed. It’s because it makes us appreciate that the truth of another person is not just something that can be ripped out of them and put on display for all to see. Knowledge, when it has to do with another human being, can’t be separated from a relationship.
In ordinary friendships, it is the journey of coming to know someone that is more important than the actual knowledge we come to possess. As I heard in a recent film, the words ‘I’ve never told anyone that before’ are even more important than what was actually told.
We let someone in gradually. We choose how much to share, and when to share it; and this depends on how much we trust someone, and how much they trust us, and how far along the road we have come together. It’s not that anyone has a right to lie. But we do all have a right to disclose ourselves gradually, on our own terms. Discretion and reticence are the background virtues that allow intimacy and friendship to have any meaning.