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Experiment raises ethical questions about using rats in pain research

A cruel experiment carried out by researchers in Japan has raised ethical questions about using rats in pain research. According to the new experiment, rats can recognise the facial expressions of other rats.1 What’s more, experts believe that they actually use these expressions to communicate, just like humans do.

Scientists in Japan took photos of rats grimacing in pain and rats with normal expressions and mounted them onto the walls of two different cages joined together by a small corridor. Young rats were then placed one at a time into the cage corridor and left to explore both cages for 10 minutes. Disturbingly, the researchers had previously given the photographed rats electric shocks to make them grimace.

They found that the rats spent significantly more time in the room that displayed the photos of the happier rats and tended to avoid the images of the suffering rats. The researchers claimed that these findings show that rats are able to tell how another rat is feeling just by reading their facial expressions and that they may use facial expression to warn each other of danger or as a cry for help.

Rats are highly social and intelligent animals and findings such as these should raise serious ethical questions about their use in experiments. Dr. Jeffrey Mogil, a Canadian neuroscientist who uses rats in pain research, admitted “The more we do experiments like this, the more we wonder if we should do experiments like this”.2 We couldn’t have put it better ourselves.



1.       Receiving of emotional signal of pain from conspecifics in laboratory rats. (2015). Royal Society Open Science, 2: 140381. Original article can be found here:

2.       Rats see the pain in other rats’ faces. (2015). Science: