Some interesting experiments on rat empathy from the article:
> "It all began with a study in which the rats refused to press a lever to obtain food when that lever also delivered a shock to a fellow rat in an adjacent cage. The rats would rather starve than witness a rat suffering. Follow-up studies found that rats would press a lever to lower a rat who was suspended from a harness; that they would refuse to walk down a path in a maze if it resulted in a shock delivered to another rat; and that rats who had been shocked themselves were less likely to allow other rats to be shocked, having been through the discomfort themselves. Rats care for one another."
> "In 2011, the issue of rats’ empathy resurfaced when a group of scientists found that rats will reliably free other rats who are trapped inside a tube. It was not that they were merely curious or wanted to play with the apparatus: if it was empty or contained a toy rat, they would tend to ignore it. And the tube wasn’t easy to open – it required effort and skill – so it seems that the rats really wanted to free their fellow rat."
> "It all began with a study in which the rats refused to press a lever to obtain food when that lever also delivered a shock to a fellow rat in an adjacent cage. The rats would rather starve than witness a rat suffering. Follow-up studies found that rats would press a lever to lower a rat who was suspended from a harness; that they would refuse to walk down a path in a maze if it resulted in a shock delivered to another rat; and that rats who had been shocked themselves were less likely to allow other rats to be shocked, having been through the discomfort themselves. Rats care for one another."
> "In 2011, the issue of rats’ empathy resurfaced when a group of scientists found that rats will reliably free other rats who are trapped inside a tube. It was not that they were merely curious or wanted to play with the apparatus: if it was empty or contained a toy rat, they would tend to ignore it. And the tube wasn’t easy to open – it required effort and skill – so it seems that the rats really wanted to free their fellow rat."