Even Some Rodents Display Empathy

For a long time, scientists thought consolation was a uniquely human trait. This barrier separating humans from animals is being battered down by species after species.

Animals do the most amazing things. Read about them in this series by Janaki Lenin.

Among prairie voles, both parents take equal responsibility in rearing offspring Credit: Todd Ahern

Among prairie voles, both parents take equal responsibility in rearing offspring Credit: Todd Ahern

We hug our friends when they are unhappy and comfort them. From the time we are two-year-olds, we feel our buddies’ pain. For a long time, scientists thought consolation was a uniquely human trait. This barrier separating humans from animals is being battered down by species after species.

In recent decades, scientists showed great apes, dogs, crows, and elephants commiserate with their buddies. Since they are clever creatures with complex social lives, scientists thought animals comforting others needed high-powered intellect.

How do we know when animals console each other? What do we look for?

An uninvolved spectator provides solace by licking, grooming, or touching a miserable individual. So say primatologists Frans de Waal and Angeline van Roosmalen.

Chimpanzees console each other by touching, hugging, and kissing. To researchers, this behaviour indicates empathy. Monkeys, however, show a limited display of empathy, not to the degree great apes do. When even these intelligent creatures appear insensitive, it comes as a surprise when scientists recently declared that prairie voles comfort their friends and mates.

The prairie vole is a brown mouse-like creature, smaller than a palm squirrel. It’s among the few animals that are monogamous for lifeWhat made scientists from Emory University, Georgia, U.S., look for empathy in these little rodents?

Mated pairs spend a lot of time together. They cooperate and show concern for each other. “Since prairie voles are able to form these kinds of attachments, we believed they would exhibit instinctive pro-social behaviour to others in distress, or so-called emotional empathy,” Elissar Andari, a neuroscientist and one of the authors of the paper, told The Wire. “By studying these species, we can also compare them to the closely related meadow voles.”

“We thought that the basic instinct to notice and respond to distress in others might be much simpler and more widespread than was previously believed,” added James Burkett, the main author.

The researchers tested if these voles responded to anxiety in others. They separated pairs of voles that were mates, siblings, or long-term cage-mates. They gave a mild electric shock to the feet of one group, the ‘demonstrators.’ Although the other group didn’t see their partners’ getting zapped, they were called ‘observers.’

The researchers reunited the two groups and watched. Even though observer voles had no idea what had happened to their mates, they immediately began licking them and didn’t give for up to 10 minutes. When the scientists reunited the pairs without delivering any shocks, the observer voles didn’t spend as much time grooming their mates. The rodents seemed to gauge if their partners were stressed and in need of consolation by merely seeing them.

Consolation helped the agitated voles become normal again. The level of corticosterone, the stress hormone, in their blood voles didn’t surge.

A prairie vole consoles another. Credit: Zack Johnson

A prairie vole consoles another. Credit: Zack Johnson

When researchers didn’t allow voles that received shocks to reunite with their mates, the animals remained scared and agitated. Observing them through a clear perforated sheet, their observer mates also grew afraid, anxious, and had higher levels of corticosterone. Viscerally mimicking another’s emotional state is a symptom of empathy, say the authors.

The research team notes that this degree of commiseration was reserved only for known individuals. When they saw unfamiliar voles with high-stress levels, they didn’t rush to console them. Humans are similarly biased too.

We feel empathy when the hormone oxytocin kicks in. The chemical is linked to maternal care and pair-bonding, and it also enables us to mind-read another’s state of mind. This empathy-causing chemical acts on a particular part of the brain called anterior cingulate cortex. This area not only regulates blood pressure and heart rate but is vital for empathy.

“Unlike meadow voles, prairie voles have a considerable amount of oxytocin receptor, a sensor for oxytocin, in key emotional brain regions that is crucial for bond formation,” says Andari.

The researchers gave a shot of oxytocin-blocker to observer voles’ anterior cingulate cortex and watched their behaviour. The oxytocin-challenged observers didn’t show any concern for their partners. So the interaction of oxytocin with the cingulate cortex was essential for empathy.

If voles, not known to be brainy like chimpanzees, can console, then the evolutionary origin of empathy must go farther back. This means empathy is likely to be more common among animals, and it doesn’t need any great cognitive abilities.

“Scientists have been reluctant to attribute empathy to animals, often assuming selfish motives,” says Frans de Waal, one of the authors, in a press release. “These explanations have never worked well for consolation behaviour, however, which is why this study is so important.”

Although animals as far apart as humans and prairie voles console, it doesn’t mean meadow voles can. They behave so differently from prairie voles, they could  belong to different families. Meadow voles are promiscuous, and while the males are gallivanting, females single-handedly rear their offspring. In experiments, these rodents weren’t considerate to their stressed peers. The authors say consolation “emerges only under particular social and evolutionary conditions.”

Why is empathy so hard to find among animals? Does feeling empathy come at a cost to them?

“Empathy can involve a certain degree of sacrifice,” says Burkett. “When we share in the pain and sorrow of others, we sacrifice our own happiness and calm to feel with them. When we are motivated to comfort and console others, we sacrifice our time and energy to benefit them. However, highly social species, like humans and prairie voles, can also benefit from showing empathy and comforting others, in terms of peace, cooperation and community. In this way, consoling can be considered an altruistic behaviour.”

If humans and prairie voles share a common evolutionary heritage, is it possible meadow voles and other rodents feel empathy but don’t know how to express it?

“It is possible that other rodents have other forms of expression that can be more subtle and less explicit to the human eye,” says Andari, who studies autism and neurobiology of human social behavior in conjunction with animal research. “Hence, it would be more difficult to observe or measure. I believe that incorporating more behavioural neuroscience approaches into molecular science is crucial for making substantial progress in psychiatry.”

Scientists use such animal studies to help humans with mental health issues, including autism, schizophrenia, and psychopathy.

“I previously found that giving intranasal oxytocin to patients with autism helped them to attend more to social cues and better understand implicit social contexts,” says Andari. “By studying consolation in prairie voles, we can understand the neural circuitry and unravel the role of molecules such as oxytocin in triggering such behaviours. Since oxytocin has a crucial role in emotional empathy, it could help alleviate socio-emotional dysfunctions in several psychiatric disorders such as psychopathology and autism.”

Until researchers find other animals that empathise, this lowly rodent is the odd entrant to the rarefied world of empathisers. The study was published in the journal Science on January 21, 2016.

Janaki Lenin is the author of My Husband and Other Animals. She lives in a forest with snake-man Rom Whitaker and tweets at @janakilenin.

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