”Aristotle thought that it was only humans who laugh, but he was wrong,” says Peter Gärdenfors, professor emeritus of cognitive science at Lund University.
Research shows not only that most mammals laugh but also some birds, such as New Zealand’s playful parrot, the kea (nestor notabilis). The difference is that the layman often cannot recognise animal laughter, as it is expressed in ways other than the bubbling joy exhibited by humans.
”Almost all mammals laugh silently or in other ways to humans. The exceptions are elephants and sea lions, which laugh out loud, just like us,” says Peter Gärdenfors.
The sea lion that started to laugh
Peter Gärdenfors shows a film clip of a sea lion gently rolling down a slope.
”It’s just like a child might do to amuse themself. But down at the beach there are tourists and a woman bathing in the sea. The sea lion dives under the surface and then suddenly appears next to the woman and scares her – the sea lion then laughs out loud at this,” says Peter Gärdenfors.
Research that came to life
One of the longtime stumbling blocks in research on laughter among animals has been determining whether it really was laughter – or just a sound that means something else.
A breakthrough was made a few decades ago when the researchers Jaak Panksepp and Jeff Burgdorf, who work mainly in the USA, discovered that rats emitted a high-frequency sound when they played.
The sound was around 50 kilohertz, far above the human hearing limit of about 20 kilohertz.
”When they later tickled the rats’ bellies, the high-frequency sound became more intense, and the researchers realised they were onto something. Jaak Panksepp then established 12 criteria for what could be considered as laughter,” says Peter Gärdenfors.
Around 20 years later, the researchers Gregory A. Bryant and Sasha Winkler, also based in the USA, produced an overview of the play signals of 65 different mammals, one kangaroo species and four bird species.
The panting of dogs, the high-pitched call of parrots and the ultrasound squeaks of rats are all examples of sounds that can be considered as equivalent to human laughter.
Genuine laughter is a binding force
”There is always a link between play and laughter. Tickling or wrestling games are perhaps the most fundamental behaviours that make both humans and animals laugh,” says Peter Gärdenfors.
Other criteria include laughter arising as a reaction to something surprising, always in a social context – and never in connection with pain or danger.
”Laughter invites play and also indicates: ‘I am neither dangerous nor afraid’ – we can continue the game,” says Peter Gärdenfors.
The research also shows that spontaneous play among children and young animals is crucial for motor skills, social training and the ability to form relationships.
One of Panksepp’s criteria is therefore laughter’s role as social cement that reduces the risk of aggression and conflicts. But laughter is also age-related.
”Children laugh a lot more than adults. A lot of the spontaneous play disappears in puberty. It’s replaced by organised games, such as sport, and humour in the form of jokes and puns. Adults laugh via humour – but animals play,” says Peter Gärdenfors.
Slapstick is popular among animals and humans
However, we do share with certain animals the ability to laugh at slapstick.
”Just like we laugh at Charlie Chaplin, apes can laugh when someone falls off a branch. And, exactly like humans, they can think it’s funny to scare someone – as long as it’s not dangerous,” says Peter Gärdenfors.
Genuine and false laughter
People are highly sensitive to the difference between genuine and false laughter. Genuine laughter is infectious. We are instinctively drawn to someone who is laughing and children also prefer adults who laugh naturally.
”When Panksepp conducted the experiment on rats, he saw that young rats were more attracted to the hand that tickled them than the hand that just stroked them,” states Gärdenfors.
However, all laughter is not positive. Nervous laughter may be perceived as sycophantic while mocking laughter can be used to exclude and ridicule rather than as a binding force.
The fact that both mammals and birds can laugh indicates that laughter is an old evolutionary ability that nature has chosen to retain. It is joy, play and togetherness – but also a complex social tool.
”We don’t know exactly why laughter works like it does, but it seems to be necessary for both humans and animals,” concludes Peter Gärdenfors.
