Rats 'capable of showing empathy'
Rats display human-like empathy and will unselfishly go to the aid of a distressed fellow rodent, research has shown.
The results of an experiment in which rats opened a door to free trapped cage-mates astonished scientists.
No reward was needed and not even the lure of chocolate distracted the rescuing rats.
"This is the first evidence of helping behaviour triggered by empathy in rats," said US study leader Professor Jean Decety.
"There are a lot of ideas in the literature showing that empathy is not unique to humans, and it has been well demonstrated in apes, but in rodents it was not very clear.
"We put together in one series of experiments evidence of helping behaviour based on empathy in rodents, and that's really the first time it's been seen."
The study, conducted at the University of Chicago, involved placing two laboratory rats which normally share a cage in a test arena. One rat was held in a closed tube with a door that could only be nudged open from the outside.
The second was allowed to roam free outside the clear plastic tube, able to see and hear its trapped cage-mate. Once the free rat learned by trial and error how to free its companion, it did so almost immediately.
Most strikingly of all, rats still prioritised their cage-mates when offered the option of "freeing" chocolate chips from a second restrainer tube.
The research is reported in the journal Science.