How Does A Polygraph Test Work?

We’ve all seen the lie detector test in one medium or another. If you’ve watched a cop show, then you may well have noticed people hooked up to a machine and asked a series of questions to prove or disprove guilt. However, people can look at these things on the television for years and then not understand how the lie detector tests work. We’re going to be taking a look at how the actual technology does its job, to bring you up to speed on the science behind lying.

So, a machine can tell if I’m lying?

While the idea may seem far fetched, it has been in use for some years now as a way to prove if someone is telling the truth or not. What people may not be aware of is that there is a particular set of processes and biological changes which occur when you tell a lie, and you know that you’re lying. Usually, the heart beats faster, you sweat more, and your breathing accelerates. These changes, while subtle, are easy to detect with sophisticated machinery. And this machinery is actually how people can identify if you’re telling a lie or not.

What a lie detector does is registers these subtle chances in those biological processes to determine if someone is in fact lying. When you are first hooked up to it, the machine records all of your baseline vitals. These are the things like your resting heart rate, your respiration levels, and your perspiration levels. What examiners will typically do is ask one or two control questions, which may well be things like ‘have you ever told a lie?’, or ‘have you ever broken the law?’. Most people will answer no to both of those questions to seem like honest people, but in truth, we’ve all lied to someone or crossed the road when we shouldn’t have done. This will then generate an increase in all of those biological processes, and this forms the basis for identifying when you’re lying because whenever you do those same process will rise again.

The lie detector will only register the lies you tell as being actual lies if they generate more of a change than the control lie which was given at the very beginning. Therefore, if you tell a dangerous lie, then the detector will be able to identify if you’re trying to hide something.

Overall, lie detector tests are built to catch people out, and they work through the identification of changes in things like your perspiration and heart rate. The lie detector test is used in many different scenarios, but they all work in the same way, by measuring changes in those conditions and using them to determine if someone is lying or if they’re not. Lie detector tests are necessary for getting the truth from a situation, but they should also be used with caution, as the innate sense of anxiety that most people feel can work against them.