Faced with danger, the human body instructs blood vessels to pinch off the flow to the face and extremities, sending more blood to the muscles and body core so you’ll be pumped up for either the flight or the fight. This is due to a combination of the autonomic nervous system, the fight-or-flight control system.
Heat-sensing cameras can pick all this up can are now sensitive enough to look for tweaks in the blood flow which vary with different emotions. Tiny wafts of heat flowing across the face can, in theory, indicate guilt, anxiety, fear, sexual arousal and so on.
An area of new research is with post-traumatic stress disorder
(PTSD). In a pilot study of bank tellers who have been robbed, a team of researchers have reported that tellers with mild PTSD have amped-up fear responses that show up in their facial heat signature.
By recording thermal video of 20 bank tellers who had been robbed at gunpoint in the last 18 months, Arcangelo Merla and colleagues at the University of Chieti carried out a classic fear conditioning experiment. Science News
notes that the researchers showed the tellers a series of happy, neutral or angry faces. Then a blast of loud white noise startled the tellers, and a video camera recorded their face’s heat as they learned to associate the face with the scary noise. The idea here is that people with PTSD have a heightened startle response in these kinds of situations.
Some of the blood drained out of each participants face when they were startled; that’s normal. Half the tellers had been clinically diagnosed with mild PTSD; the other half had no symptoms. Those with PTSD cooled off more, by up to 2 degrees Celsius, and took longer to recover than those without.
The researchers hope that the thermal imaging of PTSD patients could eventually help to identify mild PTSD and to monitor how well treatments are working.
The findings have been reported to
the journal Neuroscience
, in a paper titled “Thermal signature of fear conditioning in mild post traumatic stress disorder”.