As an intern at COSMOS Online:
The mere observation of a familiar mouse in pain has been found to affect the observing mouse's own pain sensitivity. This behaviour, say researchers, suggests empathy, a trait that is thought to be unique to higher primates, and possibly to humans alone.
Mice were subjected to a ‘writhing' test, in which they were injected with 0.9 per cent acetic acid, which caused abdominal pain. The pain response of a mouse caged with another, familiar mouse, also in pain, was markedly higher than that of a mouse housed individually, and higher still than that of a male mouse observing an unfamiliar, unaffected mouse.
"We were following up a previous finding suggesting mice were communicating with each other, and that this sort of social interaction could modulate pain," said Jeffery Mogil, Professor of Pain Studies at the McGill University in Canada, and lead author of the paper that was published on Friday in Science.
"When all the data was collected, empathy was simply the best explanation for what we observed," he said.
The observations of Mogil and his team could not easily be explained by stress, imitation or conditioning. However, Mogil asserted that the study does not claim that mice have ‘sympathy' or ‘altruism', both of which are higher forms of empathy. Instead, mice are being attributed with what he called "the lowest level of empathy: emotional contagion".
Emotional contagion is the tendency to express and feel emotions similar to those perceived in others. It is the phenomena responsible for 'contagious yawning' in humans.
These findings imply the communication of pain between mice. Further experimentation revealed that pain was communicated visually.
The study may shed light on the effect of social interactions on chronic pain behaviour in humans, as well as the behaviour of animals.
"If mice have empathy, it stands to reason that all mammals should," Mogil said.
