AI Lie Detection from Skin Signals

By Dustin Shaw

In March of 2011, an article in New Scientist gave away the details of a mock-up experiment in the psychology lab at Maastricht University. It was designed to test lie detection among a group of people or suspects and weed out the ones who lie from the ones who don't. This study of detecting lies via skin signals is to address what's lacking in the traditional lie detector machine and polygraph test questions. The experiment's proponent, Ewout Meijer, said that most of today's security threats were from terrorist groups who involve not one but multiple suspects.

The experiment took place in a bar in Maastricht University in the Netherlands where twelve students are given one envelope each marked with "Top Secret." Inside the envelope are plans for a certain terror attack somewhere in the country. The go


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al is that the students must tell no one. Later on, the students were arrested under suspicion of terrorist activities; they were interrogated using the so-called concealed information test (CIT). Specially designed sensors measure their skin conductance or the moisture levels in their skin. Various mathematical techniques which were adopted from artificial intelligence were then used to analyze the findings, thereby figuring out what the students were hiding.

With the polygraph-based lie detection method, the determination of whether or not deceit is taking place is done via a series of questions about the crime. The responses are then recorded on a polygraph, which measures the physiological signals like pulse, respiration rate, and skin conductance. This method is normally inconclusive and unreliable. Meijer's CIT experiment aims to see if any of the suspects react strongly to a specific question in a series of similar questions. During the mock-up experiment, the twelve students were questioned while measuring their skin conductance through two small electrodes on their fingers. The students were asked a set of queries which included possible dates, cities, and specific targets for the planned attack, including the correct detail for each question. The students were all told to answer "no" to all the questions.

If the suspect is guilty, the question which pinpoints an element of the plot will bring about an autonomic nervous system response or an arousal response; this will register a stronger signal than the other questions in the series. This triggers a spike in both the skin conductance and the EEG signal called P300. An innocent person's physiological response will not trigger any spikes.

It is helpful to understand how the process of lying and its biometric patterns work. That knowledge can be handy not just in workplace or familial situations but also in the day to day life.