As Valentine's Day fast approaches, many people in the thralls of a new relationship may find themselves wondering, "Does he/she really love me?". Well, if those people have access to a thermal imaging camera, they may just get their answer – at least, so a group of researchers at the University of Granada tells us.

For their study, the scientists used a group of 60 volunteers consisting of men and women aged 24 to 47 years old. All of them had started a new relationship within the past few weeks, and described themselves as being in love "in a romantic way."

Each person was observed through a thermographic (heat-imaging) camera, as they sat naked in a room looking at images on a computer screen. Half of the people were shown photos of their romantic partner (as pre-selected by them) while the other half looked at photos of family and friends, or at images specifically chosen to produce feelings of anxiety.

The scientists observed that when viewing the images, members of the first group showed a 2-degree Celsius body temperature increase in areas such as their cheeks, hands, chest, genitals, and around their mouth. That change didn't occur with the control group.

A test subject's baseline thermal reading (top), and one taken as they view images of a lover (bottom)(Credit: University of Granada)

In another test, subjects' dominant hands were placed in a bowl of 0º C (32º F) water for two minutes, taken out and dried, then filmed with the camera for six minutes – that's the amount of time it should take for a healthy person's hand to recover to normal body temperature.

Members of the first group beat that time, however, with their hands recovering in an average of just four minutes. According to the researchers, this is because feelings of romantic love cause the blood vessels to dilate, increasing blood flow.

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