Hot day? Cool yourself down by watching a video about someone being cold, researchers are saying, thanks to a new study that shows the feeling of being cold is contagious, whereas the feeling of hot is not.

A team of neuroscientists led by Ella Cooper from the University of Sussex and John Garlick from University College London, both in the UK, gathered together 36 volunteers who watched eight different three-minute videos that depicted actors with either their right or left hands in visibly warm or cold water, or their hands in front of the water as a control component. No emotional cues were given by the actors to show pain or discomfort.

Before and after each video was watched, the temperatures of the volunteers' right and left hands were measured and compared to see if any change had occurred. The temperature in the room was managed and the volunteers were asked to keep their hands as still as possible to minimise changes in temperature due to muscle movement. Even the tiny amount of heat that comes off a television screen was accounted for.

"While watching the warm and neutral videos did not produce any changes in subjects' hand temperature, watching the cold videos caused a small, but unmistakable drop," says Ross Pomeroy at Real Clear Science. "The temperature of subjects' right hands fell by an average of 0.1 degrees Fahrenheit, and the temperature of their left hands fell [by] 0.4 degrees. There was no change in heart rate."

So we're talking about the tiniest fraction of a degree Celsius - barely anything, but it's still something, just from watching a video, and that's fascinating.

Publishing their results in the journal PLoS ONE, the team suggest that the reason the warm videos didn't provoke a physiological response in the volunteers while the cold videos did could be because while the steam coming off the warm water indicated that it was warm, perhaps it wasn't as visible to the volunteers as the ice cubes floating around in the water of the cold videos. That, and the fact that previous research "has highlighted that temperature decreases are typically easier to elicit and of greater magnitude than temperature increases," they report.

Interestingly, the team got the volunteers to self-report their levels of empathy, and these measurements actually predicted their differences in sensitivity to the temperature contagion. 

This means the researchers can add a new physical condition to the phenomenon of emotional contagion - the tendency for two individual people to mimic each other's expressions and emotional states, the researchers concluded. They explain further in the paper:

"Emotional contagion is thought to be mediated by mirror neurons, brain cells that fire both when an animal performs a certain action or observes that action. The study also broadly substantiates an extreme case of human temperature fluctuation documented in 1920 by scientist J.A. Hadfield, who worked with a patient who was able to selectively adjust their right and left hand temperature by as much as 5 degrees Fahrenheit through suggestions of heat or cold."

Brb, downloading Home Alone 2: Lost in New York in prepapration for this Friday's 31-degree stinker.

Source: Real Clear Science