Crossing fingers may not bring good luck, as some believe, but it can have an impact on pain, according to scientists.

The superstitious action was found to affect a well-known pain experiment known as the ‘thermal grill illusion’, which involves heating the index and ring fingers and applying a cold stimulus to the middle finger. When this is done, a sometimes painful sensation is induced in the middle finger, even though it is actually cold.

Scientists demonstrated that crossing the middle finger over the index finger helps alleviate the paradoxical feeling. However, if the index finger was cooled and the middle and ring fingers warmed, the burning sensation increased when the middle finger was crossed over the index finger.

Lead researcher Elisa Ferre, from University College London, said: “Our results showed that a simple spatial pattern determined the burning heat sensation.

“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.”

The thermal grill experiment produces burning sensations because of a three-way interaction between nerve pathways to the brain.

Warmth applied to the ring and index fingers blocks the brain activity that would normally be driven by making the middle finger cold.

“Cold normally inhibits pain, so inhibiting the input from the cold stimulus produces an increase in pain signals,” said Ferre. “It’s like two minuses making a plus.”

The findings are published in the journal Current Biology. Co-author Patrick Haggard, also from University College London, said they suggest that similar interactions may contribute to the ‘astonishing variability’ of pain.

He added: “Many people suffer from chronic pain, and the level of pain experienced can be higher than would be expected from actual tissue damage.

“Our research is basic laboratory science, but it raises the interesting possibility that pain levels could be manipulated by applying additional stimuli, and by moving one part of the body relative to others.

“Changing the spatial pattern of interacting inputs could have an effect on the brain pathways that underlie pain perception.”