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A polygraph, also commonly known as a lie detector, is an instrument that identifies changes in a person’s physiological state to determine whether someone is lying or not. Lie detector test records blood pressure, heartbeat, respiratory patterns, and perspiration. Polygraph tests are sometimes used in pre-employment screening to evaluate the candidate’s honesty.
The machine behind a polygraph test was invented in 1921 by several scientists. The idea behind it is simple – when a person lies, the level of stress increases. And this level can be measured via blood pressure, heart rate, and other physiological responses.
As soon as the machine was invented, it gained an interest in terms of investigations and court proceedings. It was first used in court in 1923 but the ruling was that it is not appropriate in the trial until general acceptance is achieved. Even a century later, polygraph results are not always used in court. To this day, the scientific community has very different opinions on lie detector reliability and its results.
As for polygraph screening in hiring, it also has a long history. In the US, it started in the 1960s with the testing of job applicants by government agencies. In 1964, Congress ruled a directive to regulate the use of lie detector tests in employment. It also stated that the results should be treated as supplementary for any investigation.
The next major turn happened in 1983 when President Ronald Reagan allowed government agencies to use a lie detector test to find out the people behind information leaks. But this was revised in just 3 months because of general disagreement with such a policy. Currently, the Employee Polygraph Protection Act (EPPA) prohibits the majority of private employers from using polygraph tests as pre-employment screening.
However, there are several exceptions for specific fields where polygraph tests can be used, namely:
Overall, the employee polygraph test is used to identify honesty about work history, moral character, or potential illegal actions. The purpose of polygraph testing here is to determine whether applicants pose a risk to the company or public safety. For example, such testing is usually used in the employment process when it comes to police officer jobs, military, or firefighters. Because a prospective employee in these fields needs to meet the specific requirement not to cause any harm to others.
Also, the pre-employment polygraph test requires employees’ consent as defined by the EPPA.
There are several questions raised when it comes to employment polygraph test usage. The main one is how accurate such tests are. And there is no ultimate answer, that’s why the usage of lie detector tests is limited even in court and criminal investigations.
The instrument can only show the vital signs of higher stress. So if an applicant is stressed while giving an answer about illegal drug use, it can be a sign of dishonesty. However, lie detector tests cannot identify lying, despite their name. It can only show whether a candidate is more stressed during an answer or not. And there are many other reasons why someone might feel stressed or experience high blood pressure.
There are also specific medications and medical conditions that might influence lie detector tests and results.
Another factor to keep in mind is the examiner. Not only should they be licensed, experienced, and bound. But they also need to be very precise with formulating questions during the test. After all, they are interpreting the answers and polygraph machine results, and when interpretation is involved, there is always a place for perception bias.
Although it might be beneficial for employers to know about an applicant’s credit background, insurance history, or drug testing, a polygraph exam is prohibited in the hiring process with a few exceptions. Of course, the legislation depends on the country of residence and in some countries polygraph testing might not be controlled so strictly by federal law.
But overall, employers have to know exactly what they can do and what procedures should be held before introducing pre-employment polygraphs into the job interview process.
Another important aspect is the morality of such pre-employment tests. It is recognized as a violation of personal rights. And there are certain considerations of what questions can be asked and how. Results should never be used for discrimination against job applicants. The examiner might ask provocative questions to establish the baseline for physiological reactions, which is extremely hard to monitor.
And a candidate might get the wrong impression about a company because of such a request. It certainly reduces the impression of a comfortable work environment. This might drive potential candidates to other employers.
As mentioned above, a polygraph doesn’t identify the truth or lie. It only shows individual physiological responses at a particular moment in time. Thus it cannot serve as evidence of someone’s character on its own.
There are many factors that affect the validity of such an exam, including:
To sum it all up, there are usually too many variables to determine answers as certainly truthful or not.
When it comes to gender, males and females have significantly different patterns and baselines of autonomic arousal. These differences might affect the validity of test results. There is also not enough research considering female responses. The majority of studies in this field only work with male respondents.
As of today, there is no scientific evidence to evaluate how exactly polygraphs treat different responses in terms of gender.
Before a company decides to include such a test in its process it is necessary to identify how legal it is according to local and international regulations.
A lie detector test is not very common in a hiring process. Although it might give insights into applicants and their backgrounds, the usage of this instrument is strictly regulated by the law. Also, it is not always beneficial as it doesn’t guarantee accuracy. But in some cases and industries, it is a normal procedure. This applies to governmental agencies and companies dealing with security, pharmaceuticals, or other matters of public interest.
