People generally avoid hurting others because they feel a sense of empathy, which is the ability to share or understand the feelings that someone else may be incurring. Consequently, inflicting pain on someone else would cause most people to feel remorse in response to their actions, and this is why the average human practices ‘harm-aversion.’
Empathy is a complex emotion that is often deemed a precursor to advanced intelligence in living organisms. Given what we know so far, it shouldn’t be surprising that empathy has been witnessed in some of the world’s brightest animals, including apes, dolphins, and whales, just to name a few. But a new paper published just this past week in the journal Current Biology indicates that even rats may exhibit this empathetic behavior.
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The study, conducted by a team of researchers from the Netherlands Institute for Neuroscience, involved observing rat behavior as the rodents tugged on levers and witnessed the result of their actions.
The researchers wired two levers for their experiment to see how the rats would respond – one that would dispense a tasty treat, and another that would deliver a harmless shock to a neighboring rat. The rats quickly learned which lever dispensed the treat and would yank on it as often as they fancied eating. Soon after the behavior became predictable, the cunning researchers implemented a twist – they rewired the levers so that the treat-dispensing one would deliver the shock, and vice-versa.
After the lever pull issued a shock to the neighboring rat, the acting rat heard the squeaks and quickly realized that the lever issued unpleasant sensations to another rat. Consequently, the acting rat stopped pulling that lever and instead ran for the second lever, which then issued a treat. In no time at all, that same rat began only pulling the treat-issuing lever, avoiding the deliverance of a small, albeit unsettling shock to the other rat.
"Much like humans, rats thus actually find it aversive to cause harm to others," explained Dr. Julen Hernandez-Lallement, the paper’s lead author.
While conducting these tests, the researchers also observed the rats’ brain behavior to learn how they responded to another rat in distress at the hands of their own actions. Fascinatingly, they learned that the same region of the brain responsible for empathy in humans activated when the lever-pulling rat would inadvertently deliver a shock to another rat.
"That humans and rats use the same brain region to prevent harm to others is striking. It shows that the moral motivation that keeps us from harming our fellow humans is evolutionary old, deeply ingrained in the biology of our brain and shared with other animals," added Dr. Valeria Gazzola, a senior author of the paper.
The study certainly implies that rats feel empathy toward other rats in distress, but there are a lot of other variables to consider. Perhaps rats simply don’t like listening to the annoying squeaks that another rat makes when it’s in distress, or perhaps the rats were simply seeking the food and realized that the shocking lever wasn’t giving them what they wanted.
Future research will hope to pinpoint exactly why the rats responded this way and to determine whether the rodents actually share empathetic feelings for one another, a quality that would therefore categorize rats with some of the world’s smartest animals.