Struggling to keep warm this winter? You may want to avoid other people who look cold: A new study published in PLOS ONE suggests humans experience "temperature contagion." Subjects saw their own temperatures sink after watching videos of people putting their hands in chilly water, per a press release from the University of Sussex. Their left hands became colder by an average of 0.4 degrees Fahrenheit, while their right hands' temperatures dropped by an average of 0.1 degrees, Real Clear Science reports. The researchers classified that temperature change as "significant." Such sympathetic coldness could be an adaptive trait, says lead researcher Dr. Neil Harrison.
"Humans are profoundly social creatures, and much of humans' success results from our ability to work together in complex communities," he explains. "This would be hard to do if we were not able to rapidly empathize with each other and predict one another's thoughts, feelings, and motivations." When the 36 subjects saw videos of people putting their hands in warm water, however, the subjects' body temperatures stayed the same—perhaps because the cold was more evident than the heat in the videos, Harrison notes. The "cold" clips showed blocks of ice throughout, whereas the "hot" ones only briefly showed steam at their start. "There is also some evidence to suggest that people may be more sensitive to others appearing cold than hot," he points out. Yawning is among other contagious behaviors, as Medical Daily notes—and even dogs are susceptible. (Read more cold stories.)