How do rats use empathy to prepare for danger?

Many studies have shown the tremendous abilities, individual or societal, of rats. They are able to solve basic puzzles, organize themselves into hierarchical colonies and perform complex tasks. They also manage to avoid danger in a particularly effective way. And researchers at the Netherlands Institute of Neuroscience have finally discovered a key element in this mechanism: empathy. Indeed, by recognizing and feeling the fear and emotions of their fellow creatures, rats know when to avoid an immediate danger.

Their study shows that rats can use their siblings as antennas signaling danger, being extremely sensitive to the emotions of the rats that surround them. With this discovery, new targets for the treatment of empathic disorders in humans, such as psychopathy and frontotemporal dementia, could be identified in the future. The study was published in the journal PLOS Biology.

Preparing for danger through empathy

Contrary to the idea that empathy is one-way, where one person shares the pain of another, researchers have discovered a more interactive process in which animals align their emotions with mutual influences. They put two rats face to face, then surprised one of them (the demonstrator) with a brief electrical stimulation of the paws. They then observed the reaction of the two rats (the other being the viewer).

When a rat shows a reaction of fear, the other rat also feels it. In return, the reaction of the second conditions the fear felt by the first. Credits: Yingying Han et al. 2019

"The first thing we observed is that when you see your neighbor jump, the viewer is suddenly scared too. The viewer feels the fear of the demonstrator, "explains Rune Bruls. The spectator's reaction influences the way the demonstrator feels the shock. The spectators who were less afraid reduced the fear of their demonstrators. " The fear goes from one rat to another. In this way, a rat can prepare for danger before he even sees it . "

An empathic process similar to that of humans?

In humans, attending to the pain of others activates an area between the two hemispheres that is also active when we feel pain within our own body. This is considered one of the main areas of empathy of the brain. To see if this region is the same in the rat, the team injected a drug to temporarily reduce activity in this area.

"What we observed was striking: without the region that humans use to show empathy, the rats were no longer sensitive to the distress of another rat. Our sensitivity to other people's emotions may be more like that of the rat than many thought, "explains Keysers.

An empathy independent of the familiarity of individuals

The study also revealed that empathy is independent of whether or not to know the individual. For the rats that had never met, the emotions of the other rat were as contagious as for the rats that had shared the same "house" for 5 weeks. " It really challenges our notions about the origin of empathy, " explains Valeria Gazzola.

Familiarity between individuals does not influence the ability of rats to be empathic. They show empathy for both familiar and unknown individuals. Credits: Yingying Han et al. 2019

Many believe that humans and animals are empathic because they are sensitive to the suffering of their offspring. This parental concern then spreads to empathy for the closest friends. " What our data suggests is that an observer shares the emotions of others because it allows the observer to prepare for danger. It's not about helping the victim, but about avoiding becoming a victim yourself, "says Gazzola.

A level of empathy depending on past experiences

Although familiarity with the demonstrator plays no role in a rat's empathic or non-empathic reaction, previous experience does. Efe Soyman compared two groups of observers: one who had experienced electrical stimulation in the past and one who had not. He found that while experienced observers showed high levels of empathic fear, the inexperienced ones barely responded to what had happened to the demonstrator.

This is important because it shows that emotional contagion is not an innate mechanism, but something we must learn. " Rats are like humans: the more our experiences match those of the people we observe, the more we can understand how they feel, " Soyman concludes.


Bidirectional cingulate-dependent danger information transfer across rats

Yingying Han, Rune Bruls, Efe Soyman, Rajat Mani Thomas, Vasiliki Pentaraki, Naomi Jelinek, Mirjam Heinemans, Iege Bassez, Sam Verschooren, Illanah Pruis, Thijs Van Lierde, Nathaly Carrillo, Valeria Gazzola, Maria Carrillo, Christian Keysers

PLoS Biol 17(12): e3000524.


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