There’s a developing science looking at whether we can tell when a person is lying―or not lying. The developing science shows empirically that persons who are lying about a specific thing have different characteristics than persons who are not lying about a specific thing. The problem is that the evidence is based on group studies. Basically, researchers give a group of people a task, ask some of them to lie about it and others to tell the truth, and they observe the behaviours of the people in both groups - the discipline hasn’t developed to the point where one can reliably determine whether a person is lying.
However, there are factors that strongly suggest a person is lying, such as:
Although these are likely indicators of deception in group studies, they can’t be used reliably and specifically to tell whether an individual is lying or not.
Polygraph tests, often referred to as lie detector tests, measure the following physiological variables while a person answers questions or listens to information:
These physiological responses to lying are not thought to be under conscious control. The theory is that if these responses increase during questioning, the individual is experiencing anxiety due to lying. There are three major problems:
While the polygraph test may be an effective investigative tool, the findings or interpretations of polygraph results are not admissible in court. Some police officers have reported that they do not actually care about the results or interpretation of the polygraph test, but they say it’s always useful if an individual offers to undergo polygraph examination because the investigators see it as an opportunity to interview the person.
There is no real answer as to how effective polygraph tests are for detecting deception. What can be said is that they are accurate at detecting anxiety.