While rats and other rodents are known for their expressive faces - scientists can even use facial expression to see how much pain lab animals are in during experiments - it was unclear until now whether rats' expressions were simply reactive or if they could be used to communicate with other rats.
This study, which was published in Royal Society Open Science, adds another layer to the torture many lab rats experience. If these findings are correct, not only do rats suffer while they're being experimented on, but it's also possible they can suffer when witnessing their fellow rats go through the same experience.
"That's not lost on me," Jeffrey Mogil, a neuroscientist who currently experiments on rodents and has previously documented pain in rodent facial expressions, told Science. "The more we do experiments like this, the more we wonder if we should do experiments like this."