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The most reliable scientific model to date for detecting when a person is lying, based on thermography

Scientists from the University of Granada have studied the so‑called ‘Pinocchio Effect’, which causes the temperature of the nose to decrease between 0.6 ºC and 1.2 ºC while that of the forehead increases between 0.6 ºC and 1.5 ºC when a person is lying

The new method for detecting lies in a laboratory is more accurate and yields less false positives than a polygraph: it offers an accuracy of up to 80% and 20% of false positives

Researchers from the University of Granada (UGR) have designed the most accurate laboratory model to date for determining if a person is lying or telling the truth. This method, which uses thermography techniques, is based on the so‑called ‘Pinocchio Effect’: when a person is lying, the temperature of the nose decreases while that of the forehead increases, among other facial thermal changes.

The researchers, belonging to the UGR Mind, Brain, and Behavior Research Center (CIMCYC, from its name in Spanish), point out that this system is more accurate than the famous polygraph –a measuring instrument used for recording physiological responses– and other brain‑imaging techniques used in research, since thermography offers an accuracy of up to 80% (10% higher than that of the polygraph).

Emilio Gómez Milán, lead researcher of this study, points out that the two facial regions key for measuring this ‘Pinocchio Effect’ are the forehead and the tip of the nose. “When we lie, the temperature of the tip of the nose decreases between 0.6 ºC and 1.2 ºC, while that of the forehead increases between 0.6 ºC and 1.5 ºC. The greater the difference in temperature between both facial regions, the more likely the person is lying,” the expert points out.

The reason for this phenomenon to occur is quite simple. When someone lies, the body experiences an emotional response, anxiety, which is revealed in the temperature of the nose. “Besides, a cognitive response also occurs since, for lying, we have to think, to plan our excuses, to analyze the context…, and that causes a cognitive charge in us, a strong demand for attentional control which translates into an increase in the temperature of the forehead,” Gómez Milán explains.

In other words, according to the author, “one has to think in order to lie, which rises the temperature of the forehead; but at the same time we feel anxious, which lowers the temperature of the nose.”

The UGR researcher warns that it is necessary to differentiate between the study of lying in a laboratory and in real life. “The methods we use in the laboratory are very different of those used, for example, by the Police, which uses the so‑called strategic interviewing (with questionnaires including ‘tricky’ questions and demanding a lot of details) to try and catch a liar.” True detection of lies, even carried out by professionals, is only slightly higher than pure chance (54%), and the rate rises to 60%‑70% with strategic interviewing.

Its use in airports and refugee camps

“The ideal case would be to combine both methods, strategic interviewing and thermography, moving our system to, for example, police stations, airports or refugee camps. That way, it would be possible to detect if a criminal is lying or to know the true intentions of people trying to cross the border between two countries,” Gómez Milán says.

In order to carry out this study, published in the Journal of Investigative Psychology and Offender Profiling, the researchers worked with a sample of 60 Psychology students from the University of Granada, who underwent a series of tasks with the thermographer.

One of those tasks was to make a telephone call of about 3 to 4 minutes to a close person (partner, mother, friend, etc.), in which they should tell a significant lie made up by themselves (e.g., that they saw a celebrity or that they had had a car accident).

On the other hand, the control group, also monitored by the thermal camera, would make a similar call, but telling to the person at the other end of the line what they were watching on the computer (that is, gross images of mutilated bodies and car accidents).

“In both cases, the circumstances made them feel anxious, but the experimental group experienced the so‑called ‘Pinocchio Effect’ in the nose and the effect of ‘mental effort’ in the forehead, which allowed us to monitor the lie,” the researcher explains.

The author warns that, despite the fact that this new method for detecting lies is an improvement on existing ones, “there’s no method with an accuracy of 100%, since the difference between truth and lie is quantitative, not qualitative. However, with this method we have achieved to increase accuracy and reduce the occurrence of ‘false positives’, something that is frequent with other methods such as the polygraph.”

Bibliographic reference:

The Mental Nose and The Pinocchio Effect: Thermography, planning, anxiety and lies

  1. Moliné, E. Dominguez, E. Salazar‐López, G. Gálvez‐García, J. Fernández‐Gómez, J. De la Fuente, O. Iborra, F.J. Tornay, E. Gómez Milán

Journal of Investigative Psychology and Offender Profiling, Volumen 15, Issue 2, 2018.

DOI: https://doi.org/10.1002/jip.1505

Images:

Emilio Gómez Milán, UGR researcher

Efecto Pinocho

One of the subjects participating in the study makes a phone call lying to the person at the other end of the line. In the thermal image, the temperature of the nose has decreased while that of the forehead has increased

Two thermal images corresponding to the beginning and the end of the lie: the decrease in the temperature of nose and hands and the increase in the temperature of the forehead are noticeable

Contact info:

Emilio Gómez Milán

Department of Experimental Psychology, University of Granada

Phone number: (+34) 958 240 665

E‑mail: egomez@ugr.es