The stress of being around strangers causes people to be less empathetic, according to a new study by McGill University.

A team of researchers compared the reactions of undergraduate students to the pain of putting their arm in ice water in several different scenarios - alone, with a friend, with a stranger, between two strangers given a stress-blocking drug, and between two strangers who had spent 15 minutes playing the video game "Rock Band" prior to testing. 

When the students were asked to rate the pain they felt from the ice water, it didn't appear to make a difference if they were alone or with a stranger. The pain was more intense, however, when sitting with a friend. 

The ice water was also more painful after playing 15 minutes of "Rock Band" with a stranger, which suggests that meaningful levels of empathy can be generated even through superficial bonding experiences. 

"It would seem like more pain in the presence of a friend would be bad news, but it's in fact a sign that there is strong empathy between individuals -- they are indeed feeling each other's pain," McGill University psychology professor Jeffrey Mogil, senior author of the study, said of the findings. 

Mogil previously performed the same study on rats in his lab and received the same results. 

"These findings raise many fascinating questions because we know failures in empathy are central to various psychological disorders and even social conflicts at both the personal and societal level," Mogil said. "It's also pretty surprising that empathy appears to work exactly the same way in mice and people." 

The study was published in the journal Current Biology.