The juddering styluses of the polygraph machine, beloved by daytime TV and police procedurals, have never proved to be an effective lie detector. But artificial intelligence and brain-scanning technologies have spawned startups that claim to offer a better tool.

But does it really work? As it turns out, even under laboratory conditions the polygraph is no more accurate than tossing a coin.


The polygraph is a staple of crime television shows, with detectives gleaning truth from suspects as they sweat nervously in the interrogation room. Despite their popularity, most psychologists believe that polygraphs are little more than pseudoscience.

The premise behind the test is that people’s physiological responses to questions are different when they lie. By analyzing the subject’s heart rate, blood pressure, breathing, and perspiration changes, the examiner can determine whether a person is lying by comparing their responses to control questions with those to relevant ones.

The problem is that it’s difficult to tell a lie from a genuine response. Even if a subject’s heart rate spikes during a question, it could happen for any number of reasons, including shock, anxiety, or just being nervous about taking the test itself. Plus, the control questions are often so arousing that they make nondeceptive subjects doubtful of their own answers. As a result, the accuracy of polygraphs is very low.


When you move, electrical signals in your nerves travel to your muscles and cause them to contract or tighten. Your doctor can check your muscle and nerve health with two tests, usually done at the same time: needle electromyography (EMG) and a nerve conduction study. For more info I’ll suggest you visit the website Lie Detector Test.

The test involves a healthcare provider inserting a needle electrode into your muscle to record its electrical activity. You may feel a quick, sharp pain during the procedure. The electrode picks up the electrical signaling that your muscles produce and sends it to a monitor, where it shows up as wavy and spiky lines on the screen. It also can be heard through a speaker.

Normally, muscles at rest have no electrical activity, but slight contractions of the muscle produce activity that increases as you contract the muscle more. The EMG translates this information into graphs and numbers that help doctors make a diagnosis. EMG can reveal problems with your motor nerves, muscles or the communication between them.


Eye tracking is a powerful and accurate method to understand how users interact with your app, website or digital product. It allows you to measure and analyze the metrics of a user journey based on ‘points of fixation’, which are moments during the user experience when the participant stops and focuses their attention for long enough to process information (also known as a saccade).

The system uses an infrared video camera to track where the participants are looking on the screen. It does this by reflecting light off the surface of a participant’s cornea, and then matching up the location of that reflection with where the pupil is on the screen.

This technique has many applications, ranging from recording how much a user watches an advert to how quickly they scan comparison tables. However, this type of research requires a large investment in equipment and training. Furthermore, the data can be influenced by external factors like light levels, which can affect a person’s pupil diameter.


The nerve cells in the brain generate electrical impulses that fluctuate rhythmically and form distinct patterns of activity, which can be recorded using an electroencephalograph (EEG). The technique is also known as brain-wave recording.

During an EEG, you lie down on a bed or reclining chair and remain very still. The technician will mark spots on your scalp where the electrodes should be placed. The areas might be scrubbed with a gritty cream to help ensure a high-quality reading. Then the technologist will attach flat metal discs called electrodes to your head, usually with a special adhesive. The electrodes are connected to wires that go to a machine that records the electrical signals.

The machine changes the electrical signals into visual patterns on a computer screen. If you’re tested at a hospital, you may be given a mild sedative to relax you. The sedative might affect your ability to drive or operate machinery, so you’ll need someone to take you home afterward.