New research suggests that how you feel pain is affected by where sources of pain are in relation to each other, and so crossing your fingers can change what you feel on a single finger.

Researchers at the University College London used a variation on an established pain experiment, known as the "thermal grill illusion". In the thermal grill illusion, a pattern of warm-cold-warm temperatures applied to the index, middle and ring finger respectively causes a paradoxical, sometimes painful, sensation of burning heat on the middle finger - even though this finger is actually presented with a cold stimulus.

"The thermal grill is a useful component in our scientific understanding of pain," Angela Marotta, co-lead author in the research, said in a statement. "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."

The thermal grill produces burning heat sensations because of a three-way interaction between the nerve pathways that tell the brain about warmth, cold and pain. The warm temperature on the ring and index fingers blocks the brain activity that would normally be driven by the cold temperature on the middle finger.

"Cold normally inhibits pain, so inhibiting the input from the cold stimulus produces an increase in pain signals," Dr. Elisa Ferrè, co-lead author of the study, said in a statement. "It's like two minuses making a plus."

For the study, researchers showed that this interaction was based on the spatial arrangement of the fingers. When the middle finger was crossed over the index finger, the paradoxical sensation of burning heat on the middle finger was reduced.

However, if the index finger was cooled and the middle and ring fingers were warmed, the burning heat sensation was now increased when the middle finger was crossed over the index finger.

"Our results showed that a simple spatial pattern determined the burning heat sensation," Ferrè said. "When the cold finger was positioned in between the two warm fingers, it felt burningly hot. When the cold finger was moved to an outside position, the burning sensation was reduced. The brain seemed to use the spatial arrangement of all three stimuli to produce the burning heat sensation on just one finger."

Researchers said interactions like these may contribute to the "astonishing variability" of pain.

The findings are detailed in the journal Current Biology.