THURSDAY, Dec. 8 (HealthDay News) -- Rats may have gotten a bum rap.
Far from being self-centered scroungers, a new study found that the rodents showed what looks like real empathy -- repeatedly freeing trapped companions, even when they're given the opportunity to eat chocolate instead.
This first evidence of empathy-motivated behavior in rodents suggests that this type of pro-social helping behavior developed earlier in animal evolution than was previously thought, the University of Chicago researchers added.
Anecdotal observations of empathetic behavior have been noted in non-human primates and some other wild animal species, but it had not been seen in laboratory rodents.
In the study, companion rats that normally shared a cage were put in a separate space where one was under restraint and the other wasn't. The restrained rat was kept in a tube with a door that could only be opened by a push from outside.
The researchers say the free-ranging rat appeared agitated when the other rat was kept in the tube, a state the scientists called "emotional contagion" -- feeling the distress of others.
A few days into the experiment, the free-roaming rat learned how to open the tube door, freeing the other rat. Once this was learned, the free-ranging rat made this his/her first action upon being placed in the new area.
"There was no other reason to take this action, except to terminate the distress of the trapped rats," said the study's lead author, graduate student Inbal Ben-Ami Bartal. "In the rat model world, seeing the same behavior repeated over and over basically means that this action is rewarding to the rat."
Even the lure of a tasty treat didn't seem to sway the rat from helping a trapped companion: When the researchers placed chocolate chips inside another tube, the free-ranging rat nearly always opened the tube containing the other rat first, before going for the chocolate.
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