Our understanding of what’s going on in the minds of animals has come a long way. Where once science held that animals were little more than instinctive automatons, now we understand that cats miss us when we’re gone, crows can remember human faces and hold grudges, and a number of species even have a rudimentary sense of self. We have found more and more traits in the animal kingdom that previously had been thought to be uniquely human. One trait that has been investigated in animals recently is empathy.

Cats notice a lot, but can they notice your emotional state? Image by Kate Dzikiewicz.

Empathy is defined as the ability to understand and share the feelings of another. If you ask a pet owner if animals feel empathy, they might recount a time when their cat or dog seemed to sense they were feeling poorly and came over to comfort them. As it turns out, the pet owners may be in the right, as empathy has been demonstrated in one of our most humble of animal brethren: Rats.

Rats are no strangers to scientific studies. They have been used to model everything from addiction to mutation, and a group of scientists in Japan, Nobuya Sato, Ling Tan, Kazushi Tate, and Maya Okada, decided to put them to the test where empathy was concerned.

In their experimental apparatus, two rats were separated by a door. On one side of the door, the rat was placed in water, at no danger from drowning, but very wet and uncomfortable. The wet rats had to either swim or cling to a small platform, something that an empathetic human would certainly recognize as distressing. The rat on the other side of the door was dry and comfortable, but able to clearly see its unhappy cagemate. The door between them could only be opened from one side, the dry side. Would the dry rat graciously let in the wet rat from the damp?

Ten rat pairs were put through twelve trials during the experiment. Though not all dry rats initially opened the door to let the wet rats in, by the end of 12 sessions 9/10 of the dry rats were consistently freeing their wet companions. The speed at which they opened the door increased greatly throughout the trials too.

For the next stage of the experiment, researchers switched the roles of the rats. Now, the previously dry helper rats were placed in the water and the previously wet rats were on the dry side. It was under these conditions that rat response time was fastest of all. All previously wet rats leapt into action when seeing the other rat in the water, including the one rat that hadn’t been helped by its dry counterpart in previous experiments.

Just based on these first results, it does seem like the rats were showing empathy. They helped their companions in need, and helped them faster when they had a greater understanding of what they were going through. However, rats are intelligent and curious animals. To truly see if they were motivated by empathy, it was necessary to test them in more neutral situations as well.

A helper rat assists a wet rat. SATO, N. ET AL., ANIMAL COGNITION (2015)

It can be fun to just open doors sometimes. To test whether the rats were just opening doors as play, helper rats were placed in a number of other conditions. When the wet side of the cage was empty or held only a toy rat, the helper rats were far less motivated to act. They opened the door less often, and when they did, they took over a minute longer on average to do so than if there was another rat on the other side instead.

They tested another condition too. Rats are very social animals, so it’s possible that the dry rats just wanted company when they were “helping” the wet rat. They separated the rats again in the experimental chamber, but this time both sides were dry and neither rat was distressed. When they tested eight pairs of rats this way, only one rat ever bothered opening the door to let the second rat in. This rat wasn’t very consistent with opening the door, either. It only opened the door in about half the sessions, and was in no hurry to do so when it did. Rats have apparently no urgent need to open doors for their kind when both are fairly comfortable.

Rats open doors for suffering rats, leave them shut for comfortable rats, and show only a passing interest when something other than a rat is on the other side of the door. Signs point towards rats being motivated by recognition of the suffering of others, but not even this conclusion was enough for the researchers.

Would you pull a distressed human out of the water if you saw someone offering free $100 bills in the other direction? I think most people would still stop and help their fellow human, but would a rat be able to make a similar complicated moral choice? What would happen if the rats were given the choice between rescuing a suffering cagemate or getting a reward?

In this final experimental condition, there were three rooms to the rat chamber. The central room with the dry helper rat opened into two other chambers, one with the distressed wet rat, and another with a tasty food reward, chocolate cereal.

Could rats resist the sweet treat, even if it meant abandoning their comrade to damp discomfort? In most cases, yes. Over half of the rats opened the door to the wet rat first. Rats that had been initially taught to open doors with a wet rat on the other side helped the wet rat first around 80% of the time and rats that were taught to open doors with a cereal reward helped the wet rat first in closer to 50% of trials. Even the rats that chose the treat first would still help the wet rat eventually, though some had to wait until after they were done eating.

This is a truly amazing result that really calls into question the notion of animals as creatures of pure self-preservation and instinct. Food is necessary for survival and thus undoubtedly high on the priority list for animals, but most rats still chose to help their fellow rat before feeding. Some even shared their treat with their rescued companion afterward.

It does seem apparent that rats are able to feel some form of empathy after these experiments. Considering that they are helping the other rats with seemingly no reward, one could even say that rats are altruistic.

Rats can make great pets too! Image by Inge Habex

It may be that empathetic thinking is common in the animal world, and it’s only now that we’re finally able to recognize it. Vampire bats share blood with other bats that are too sick to go out and feed. Whales have been seen sheltering and protecting sickly dolphins that can’t take care of themselves. With this in mind, it certainly doesn’t seem far-fetched to think that your pet really does feel for you when it comes over to cheer you up when you’re feeling down.

Far from being alone, humans might be in good company when it comes to feeling the emotions of others.

- Kate Dzikiewicz, Paul Griswold Howes Fellow

For more information, see: Sato, Nobuya, et al. "Rats demonstrate helping behavior toward a soaked conspecific." Animal cognition 18.5 (2015): 1039-1047.