Scientists develop an objective, thermography-based method that allows to know if a person is 'in love' or not

Their work has determined the thermal changes the bodies of the participants experienced when they contemplated an image of the person they love. This represents the world's first "love's thermal map," in the authors' words.

For this work, the UGR researchers analyzed the thermal differences between the subjects that were exposed to photos of their loved ones as opposed to those who contemplated images which produced in them an emotive response other than love (anxiety, calm, empathy…).

60 people participated in this research, healthy men and women between 24 and 47 years old, which declared to be in love in a romantic way (with passion and intimacy) and to have started a relationship few weeks earlier.

After going into the laboratory of thermography, the subjects were naked for 20 minutes in order to get acclimatized, and then they were taken their basal temperature. In different sessions, the main group watched, in a computer's screen, photos of their love relationship, chosen by them. The control group, for their part, watched images taken from the International System of Affective Images, which produced anxiety; or photos of family and friends.

The results showed that love increases in two degrees Celsius the temperature of cheeks, hands, chest, genitals, and around the mouth. However, the authors warn that "love's thermal pattern is very complex," given that it includes the co-existence of passion and sexual desire (or the lack of it), in contrast with the predominance of empathy and intimacy or compromise and social contract, for example.

In the last years, researchers from the CMCYS's Laboratory of Thermography directed by UGR professors Emilio Gómez Milán and Francisco Tornay Mejías have managed to construct the thermal map of complex feelings such us love, happiness or empathy and also of basic emotions such as joy, sadness, fear or wrath.

"Thermography shows us that passion increases the temperature around hands and face whereas empathy (the ability of 'tuning in' with the other as a person, not just as an object of desire) decreases it, especially in the nose. It's as if passion was an accelerator that turns our body on, and empathy was a brake to that activation," says professor Emilio Gómez Milán. In brief, romantic love would be a mix of passion and empathy.

The cold stress test

Nowadays, the UGR researchers are working on another method known as 'cold stress test', frequently used in Medicine for treating diseases like Parkinson's. This method consists in introducing the dominant hand (depending on the subject being right or left-handed) in a bowl with water at 0 ºC for two minutes. Afterward, they dry the hand and film it for six minutes (the time necessary for a healthy person to recover the hand's normal temperature).

"In the case of young people in love, we have observed that when contemplating images of the loved one during the thermal recovery, said recovery is accelerated and complete after four minutes because love accelerates vasodilation, whereas watching anxiety-generating images, delays thermal recovery, as it produces vasoconstriction," says Emilio Gómez Milán.

In the last years, this same research team belonging to the UGR has applied thermography to the field of Psychology, for example, to determine the so called 'Pinocchio effect' (which shows that the temperature of the nose changes when people lie), objectively measuring the duende of flamenco dancers (or 'bailaores') or the mental pain associated with the so called 'mirror-touch synesthesia'.