Tag Archives: rodents

Empathetic rats avoid hurting other rats

Credit: Pixabay.

Most humans actively try to do all they can do to avoid harming other people. Psychologists refer to this behavioral trait as ‘harm aversion’ and it is considered a fundamental cornerstone of healthy moral development. Case in point, studies point to the fact that people with violent antisocial tendencies score low on this trait. That being said, not much has been known about how harm aversion works in the brain — until now, after researchers showed that rats also actively avoid harming their own kind.

Rodent empathy

Neuroscientists at the Netherlands Institute for Neuroscience (NIN) performed experiments with caged rats where they had the choice of pressing two levers, one of which delivered a tasty treat (sucrose pellets).

After this conditioning round, the entire setup was changed such that pressing the lever that offered candy also delivered an unpleasant electric shock to the floor of an adjacent cage where another rat was stationed. Pressing the lever caused the neighboring rat to squeak in protest.

Time after time, the rats stopped pressing the lever after they figured out that this would cause pain to the adjacent rat. This was true whether or not the neighbor had previously shared a cage with the lever-pressing rat or was a total stranger.

“Much like humans, rats thus actually find it aversive to cause harm to others” explains Dr. Julen Hernandez-Lallement, first author of the study and researcher at the NIN.

Schematic of the experiment. Credit: Christian Keysers.

Previously, brain scans showed that a brain region nestled between the two hemispheres, called the anterior cingulate cortex, lights up with activity when people empathize with the pain of a fellow human.

This same region also becomes more active in rats that witness the pain of fellow rats. According to the researchers, the rats have emotional mirror neurons that trigger the animal’s own pain neurons when another rat is harmed.

When brain activity in the rats’ anterior cingulate cortex was reduced after a local anesthetic was administered, the affected rats stopped avoiding pressing the lever that harmed the neighboring 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 engrained in the biology of our brain and shared with other animals”, commented Dr. Valeria Gazzola, one of the senior authors of the study and group leader at the NIN.

This doesn’t necessarily mean that the study proves that rats have empathy and care about the welfare of other rats. Perhaps the rat stops pressing the lever because he simply can’t stand the squeaking noise, for instance. We can’t know for sure unless you ask the rodent and, unfortunately, that is not an option. But the same reasoning can be applied to humans also. How can we know for sure when a person acts out of altruism or selfishness?

The findings, which were published in the journal Current Biology, are extremely valuable nevertheless. More practically, they suggest that the anterior cingulate cortex can be targetted by pharmacological means to perhaps treat individuals who might engage in violent or psychopathic crimes.

“Whatever the motive, that we share a mechanism that prevents antisocial behavior with rats is extremely exciting to me. We can now use all the powerful tools of brain science to explore how to increase harm aversion in antisocial patients,” added Prof. Christian Keysers, group leader at the NIN.

This wasn’t the first time that researchers showed that rats have empathy traits. A study published all the way back in 1959 found rats refused to press a lever to obtain food when that lever also delivered a shock to a fellow rat (yes, just like this new study). Their protest was so strong that the rodents would rather starve than witness a rat suffering. Subsequent studies showed that rats refuse to follow a certain path in a maze if it resulted in a shock delivered to another rat or that rats who had been shocked themselves were less likely to allow other rats to be shocked.

In other words, rats seem to care about their fellow rat. The kind of care that seems to be in low supply among some humans.

Too ugly for science? ‘Ugly’ rodents and bats receive less scientific attention

A study conducted by Australian researchers found that scientific journals discourage the study of ‘ugly’ rodents and bats. This group of animals, while often endangered and critical to local ecosystems, remains grossly understudied.

Not cute enough for science? Black flying fox feeding on a palm tree in Brisbane, Australia. Photo by Andrew Mercer.

The scientists reviewed the published literature for each of Australia’s 331 mammal species and found that they can generally be split into three categories: the good, the bad and the ugly. The good are marsupials and monotremes (mammals which lay eggs), and most studies focus on their physiology and anatomy. The bad are introduced mammals, such as foxes, cats and rabbits, and most studies focus on their environmental impact and population control. Then, there’s the ugly – mostly native rodents and bats with studies focusing on … nothing, because there’s not much literature on them.

“The majority of studies on monotremes and marsupials (the ‘good’) are directed towards their physiology and anatomy, with a smaller ecological focus,” the study writes. “By contrast, introduced eutherians (the ‘bad’) have attracted greater attention in terms of ecological research, with greater emphasis on methods and technique studies for population control. Despite making up 45% of the 331 species studied, native rodents and bats (the ‘ugly’) have attracted disproportionately little study.”

According to researchers, one of the main reasons why this category is so understudies is their cryptic nature – they’re small and difficult to spot and monitor. However, there’s also another factor: with limited funding and resources, most scientists choose to focus on charismatic species, largely ignoring the ‘ugly’ category. Scientific journals are also more likely to reject such studies for being “parochial and of limited interest”.

“Current global and national conservation funding largely overlooks these non-charismatic species, and yet these may arguably be most in need of research effort,” said Professor Trish Fleming, a wildlife biologist at Murdoch University in WA, who co-authored the paper with Dr Bill Bateman from Curtin University.

Fleming asks for more funding for the ignored species and political backing to help conservation agencies protect species. She says citizen science programs could help increase research capacity.

Journal Reference.