Researchers at the Nippon Telegraph and Telephone Corporation in Japan led a group of volunteers to a dark room and asked them to place their hands on a plate lit up either in blue or red. The scientists then asked them to state which plate felt warmer. Despite the researcher's expectations, the volunteers chose blue, which is commonly associated with degrees of coldness. Ho and his team expected them to pick red because this colour is usually associated with warmth.
Ben Fogelson at Scientific American explains that red-coloured surfaces needed to be warmed an extra 0.5 degrees Celsius than the blue ones before the volunteers felt they were warmer to the touch.
“I was very surprised,” said Hsin-Ni Ho, a communications researcher at the Nippon Telegraph and Telephone Corporation in Japan and the study’s lead author, to Fogelson. “I think as most people, our expectation is that red objects should feel warm and blue objects should feel cold. We get a totally reversed result. At first I was like, ‘Oh, is something wrong?’”
This study seems to contradict previous research in which red or blue lightning made people feel warmer or colder. Ho explained to Fogelson that this may be due to the fact that this study tested how people perceive the temperatures of objects when directly touched.
Because our minds are programmed to expect red objects to be warmer than blue to the touch, more heat is required for us to notice the difference.
To confirm the results, Ho and his team conducted a second experiment in which they projected red or blue light onto the participants' hands. This time around, however, red hands made surfaces feel warm at lower temperatures than blue hands. Our brain already expects a hand to be warm, so when we touch it, Ho explained to Fogelson, we interpret it as being warmer than it is.
“When you look at a red object you expect it to be warm. You have something already in your mind,” said Ho. “The contrast between the expectation and actual temperature perception will influence what you feel.”
The results of the study were published in Scientific Reports.