Hide and squeak: scientists reveal the playful lives of rats

A rat plays hide-and-seek in this undated image courtesy of Reinhold, Sanguinetti-Scheck, Hartmann & Brecht
A rat plays hide-and-seek in this undated image courtesy of Reinhold, Sanguinetti-Scheck, Hartmann & Brecht

The next time you come across a rat darting furtively for cover, consider this: It might just want to have a playful game of hide-and-seek.

A group of neuroscientists in Germany spent several weeks hanging out with rodents in a small room filled with boxes, finding the animals were surprisingly adept at the cross-cultural childhood game—even though they weren't given food treats as a reward.

Instead, the rats appeared to genuinely enjoy both finding their sneaky human companions and being caught by them, as shown by their joyful leaps (what the Germans called "freudensprung") and ultrasonic giggles that previous work has found is a sign of happiness.

The researchers' paper was published in the influential journal Science on Thursday, and beyond the cuteness factor (or creepiness, depending on one's perspective), it offers new insight into play behavior, an important evolutionary trait among mammals.

"When you work a lot with rats over the years, you see how intelligent these animals are and how social," co-author Konstantin Hartmann from the Humboldt University of Berlin, where the other members of the team are also based, told AFP.

"But it was still very surprising to us to see how well they did," he said.

Working with adolescent male rats in a room of 30 square meters (320 square feet), a scientist would either find a cardboard box to crouch behind in a hiding role, or give the rat a headstart to find cover while the scientist searched.

Random Seek. Two trials during a ‘Seek’ session. Credit: Reinhold, Sanguinetti-Scheck, Hartmann & Brecht

Over a period of one to two weeks, the rats were taught that starting the game inside a closed box that was opened remotely meant they were seeking, while starting the game with the box open meant they were hiding.

They quickly developed advanced strategies, including re-visiting spots humans had previously hidden when they were seeking, and choosing to take cover in opaque rather than transparent boxes when they were hiding.

To help train them, the authors rewarded the rats not with food or water, which would invalidate the experiment, but with positive social interaction in the form of physical contact, explained Hartmann.

"They chase our hand, we tickle them from the side, it's like a back and forth a little bit like how you play with small kittens or puppies," he said.

The scientists suspect though that the rats were motivated not just by this interaction but that they also liked to play for the sake of play itself.

The animals would let out high-pitched giggles three times above the human audible range and would execute so-called "joy jumps" during the game—both associated with feelings of happiness.

Once they were discovered, the rats often jumped away and "playfully rehid" at a new location, sometimes repeating the process several times—indicating they wanted to prolong the play session and delay the reward.

Hide. Three trials of a ‘Hide’ session. Credit: Reinhold, Sanguinetti-Scheck, Hartmann & Brecht

Ethics questions

Play is an important part of cognitive development for adolescent mammals, and rats make for ideal models to study brain activity in humans because of their evolutionary proximity to us, which is also why they are often used in the study of disease.

Scientists are therefore keen to learn what parts of the brain's prefrontal cortex that is linked to social behaviors, are involved—but because play is a free-flowing activity, it had been difficult to study.

The team therefore attached microwires to the rats' heads that recorded their brain activity, allowing them to identify which individual neurons were linked to specific game events.

This in turn could be used for future study: for example, to look at neural development when play activities are restricted during adolescence.

But the more we learn about rat and mice social behavior, the more human-like they seem, raising difficult ethical questions about their use in medical trials and other experiments.

"I think, being aware of the cognitive abilities of an animal is really important," said Hartmann, adding it was always important to judge the value of the expected outcome against the use of animals.

"This type of research will also help other scientists to see in rats more than what you usually see when you just get the rat and use it for standard experiments, when you're not aware of what these animals can do."


Explore further

Brain circuit controls individual responses to temptation in rats

More information: A.S. Reinhold el al., "Behavioral and neural correlates of hide-and-seek in rats," Science (2019). science.sciencemag.org/lookup/ … 1126/science.aax4705
Journal information: Science

© 2019 AFP

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Sep 12, 2019
IT would be stupid to let sentimentality eliminate the use of animals as medical test subjects. As long as the testing avoids causing the animals undue pain.

Sep 13, 2019
I'm not surprised that it's Germans doing this sort of research.
American and Australian researchers would consider the findings invalid because they dare to describe the behavior in such human terms.
While the Americans think they are being rigidly scientific in refusing to do this, they are actually obeying a religiously rooted cultural imperative so deeply ingrained in American and Australian culture that even atheists are oblivious to its influence on how they perceive animals.
I'm referring to the religiously rooted notion that humans are not animals because humans have souls. That religious belief is the root of so much American and Australian bias against thinking or describing other animals using human terms, because what makes us human is a soul.

Sep 13, 2019
hmm @Jonseer. Australia's multicultural, with a nominally dominant Christianity. There are plenty of atheists who place humanity at the pinicle of existance based on a demonstrable sapience, thus allowing for the exploitation of all other species; @rrrander that would allow for your argument also. Why - because it is just so.

Sep 13, 2019
Funny thing, scientists. They find cause to denounce experimenting on rats, by experimenting on them.
I propose, that given enough time, we could tame every other creature. The reality, however, is that we are the ones being tamed.
Doubt me?
Well, as you read this article. Did you notice your growing acceptance of these little critters? When did you realize that you agreed with the researchers' views?
We are the experiment?

Sep 14, 2019
I'm referring to the religiously rooted notion that humans are not animals because humans have souls. That religious belief is the root of so much American and Australian bias against thinking or describing other animals using human terms, because what makes us human is a soul.


On the other side, you have people who argue that animals are just like people. It's the same error, just flipped around. Kinda like the kind of "atheism" that is really about denial of God rather than simply not believing in deities.

The reality is, just because rats giggle and play doesn't mean they're the same sort or degree of sentient as people are, if they are at all, and this has nothing to do with the notion of souls. The problem is that we are quick to jump to conclusions when we recognize a familiar feature. We project our own sentience to the animal in attempts to explain it.

Sep 14, 2019
Someone explained it to me rather well: when a bird flies in the sky looking for food, and it sees a wasp with the yellow rings, it doesn't think "Oh, those are warning colors, better avoid that.". It just goes the bird equivalent of "Yuck" and goes elsewhere.

When people look at the situation, we explain it almost like the wasp was consciously displaying those rings to the bird, who is consciously observing that the wasp is displaying signs of being poisonous to eat. We project the sentience to the situation to explain it, whereas in reality the whole thing happens by nature - without explicit thinking of any sort.


Sep 14, 2019
There are plenty of atheists who place humanity at the pinicle of existance based on a demonstrable sapience, thus allowing for the exploitation of all other species


The irony is, without a universal lawgiver (God), there are no objective morals and therefore the exploitation of other species - even exploitation of other people - is morally neither justified nor unjustified. You don't need to elevate people to be the "pinnacle" and justify it that way - you can just do it without any excuses because none are really needed.

It's a matter of agreeing not to do it, which is what we did with the universal declaration of human rights. Just remember that trying to say "because it's wrong/unethical" requires you to invent yourself a "god" to grant you such absolute morals, which is falling back into the original trap.

What you have to say instead is "because I don't like it", which is the truth.

Sep 14, 2019
A point of note is that not all agree to the universal declaration of human rights. It's a matter of people accepting the rule because they want the rule to apply to themselves - but if you're in a position of security where you know you can have your way either way, you simply don't have to.

So some societies, for example many of the Islamic societies, have their own version of the declaration of human rights which puts the ultimate authority in Allah, or in other words, the religious elites.

Which is to say, the appeal to ethics and morality in animal rights mirror the same in human rights: it depends on who you ask, and nobody has the ultimate answer. For example, if you believe in the UN declaration of human rights, have you any right to make other people follow the same? If so, why? Why not?

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