Researchers did a follow up experiment to some earlier rat empathy studies and found that rats were willing to help other rats even to their own detriment, but only if they had some prior familiarity with the particular strain of rats, e.g. an albino rat being bunk mates with a black and white rat. If they didn't have any previous experience with that strain of rat, they would not help. Or according to the Washington Post: "The creatures aren’t born with an innate motivation to help rats of their own kind, but instead those with whom they are socially familiar."
The rat empathy thing is interesting because it suggests an evolutionary advantage to empathy, not necessarily a "humans are special snowflakes of the animal world" reason for empathy. The articles discussing the findings use an interesting choice of words that accords -- they call the rats actions "noble" and other such language. This helps explain to me a little more why the fetishism for empathy, that people are biologically pre-programmed not only to engage in empathetic acts, but that they are also pre-programmed to find those acts appealing in the same sort of way that they crave sugar or find others attractive or not based on their pheromones.
Another interesting idea is that with all of these studies with animals and empathy (see also prairie moles), the animals will not act with empathy unless they are familiar with either the particular animal in need (spoiler alert, but see for example Ser Jaime's actions in recent Game of Thrones episodes) or at least someone of the same breed. It's like what they say about gay people or mormon people or any other people that a lot of people often have a hard time understanding or being ok with -- you just have to know one or two of them personally in order to humanize them to your own self.
What implications does this have for sociopaths, if everyday sociopaths stay hidden forever? Will people never learn to show empathy to them?