Confuse your brain and dull the pain. Thanks, science!
UCL scientists find that crossing the fingers can confuse the way the brain processes sensations – reducing pain in some cases
In the experiment, if a person just touches the hot or cold thermal pads, they will feel only hot or cold sensations respectively. But touching them together creates the illusion of burning heat, as Hannah Devlin explains at The Guardian:
“The illusion works because the hot sensation in the outer two fingers blocks the activity in a certain cooling receptor under the skin and this “inhibition” spills out to the surrounding area of the hand.
Activity in the cooling receptors in turn normally blocks the activity of pain receptors that are sensitive to extreme cold. As a result only mild cold is now needed to produce a painful burning sensation in the middle finger – hence the illusion.”
So effectively, the simultaneous heating and cooling creates an illusion because the brain is trying to reconcile a three-way interaction between the nerve pathways that are trying to send it signals about warmth, cold and pain, all at once.
The thermal grill illusion is the perfect solution for scientists wanting to experiment with and research pain sensations in humans, because it creates the feeling without causing any lasting physical damage.
“The thermal grill is a useful component in our scientific understanding of pain,” one of the researchers, neuroscientist Angela Marotta, from the University College of London’s Institute of Cognitive Neuroscience in the UK, said in a press release. “It uses a precisely-controlled stimulus to activate the brain’s pain systems. This can certainly feel painful, but doesn’t actually involve any tissue damage.”
“Cold normally inhibits pain, so inhibiting the input from the cold stimulus produces an increase in pain signals,” added one of her colleagues, Elisa Ferrè. “It’s like two minuses making a plus.”
Then, oddly enough, the team was able to show that by just changing the position of the affected fingers, they could greatly manipulate the pain levels experienced by their volunteers. When the volunteers were asked to cross their middle fingers over their index fingers, the burning sensation was alleviated.