The Impact of Nervousness on Lie Detector Tests

Many wonder how nervousness can affect the outcome of a lie detector test, also known as a polygraph test. These devices measure physiological responses such as heart rate, blood pressure, respiration, and skin conductivity. When a person is nervous or anxious, these physiological changes can sometimes mimic the signs of deception. This could lead to inaccurate results, making the use of polygraphs controversial and not widely accepted as a definitive measure of truthfulness.

Factors Influencing Polygraph Accuracy

It is no secret that being nervous can affect the results of a polygraph test. However, the level of nervousness and its impact can vary. The operator's skill in calming the subject can significantly influence the outcome. Generally, anxiety is expected during a polygraph test and is typically mitigated to some extent. If a subject is overly agitated, the test may be canceled, regardless of whether they have any guilty knowledge.

Understanding Polygraph Mechanisms

It's important to note that there is no such thing as a "lie detector" in the strictest sense. Polygraphs are based on the Law of Initial Values, which assumes that everyone, except those under the influence of certain drugs, will be nervous or anxious about taking the test. This anxiety is a given, both at the start and the end of the test. What is being evaluated are the changes that occur during the data collection process.

The test tries to minimize the impact of anxiety by including baseline questions. These questions help establish a baseline response, accounting for any general nervousness a person may have. However, the actual test questions may still cause stress, leading to changes in physiological responses that may be misinterpreted as signs of deception.

Historical and Practical Examples

A real-life example from the past highlights the nuances of polygraph testing. In 1987, a candidate officer was being vetted on a lie detector as part of the routine process. One question asked, "Have you ever had contact with another Intelligence service?" As the candidate's mind wandered, he answered "yes" without thinking, triggering no stress reaction and indicating "the truth." However, when he realized his mistake, intense distress ensued. Despite this troubling incident, the candidate was able to clear the vetting process with the help of a psychologist, avoiding major repercussions.

Pre-vetting procedures also involve a series of calibration questions to establish a baseline reaction. This means that an individual with a general high state of anxiety can still exhibit specific signs of deception. To further mitigate anxiety, polygraph operators may ask control questions at critical points to stabilize the baseline response. For instance, the operator might ask, "Is it the month of November?" while the subject is experiencing heightened anxiety.

Limitations and Controversies

Trusting the results of a polygraph test entirely is risky. In the United States, results from polygraph tests are not admissible in court. Other countries have similar restrictions or do not use polygraph tests as part of police interrogations. The South African Defense Force (SADF) dropped the use of lie detectors in 1988, deeming them relatively ineffective.

While the American intelligence community still employs polygraphs, their use is not universal. The fallibility of these tests underscores the need for careful interpretation and the importance of corroborating evidence.

Conclusion and Takeaways

In conclusion, nervousness can indeed affect the results of a lie detector test. The polygraph operator's ability to manage a subject's anxiety and the test protocol itself play crucial roles in ensuring accurate results. However, the inherent limitations of polygraphs mean that they should not be relied upon as the sole method for determining truthfulness. Always seek multiple forms of evidence and professional evaluation to ensure fair and accurate conclusions.