Aristotle once questioned what separates humans from animals. He decided it’s not language or reason. It’s laughter.
Aristotle wrote that the moment when a baby first laughs is when the child becomes fully human. According to historian Barry Sanders, Aristotle believed that “At that point, the creature moves from being a human into a human being.”
Aristotle may have been wrong about the uniqueness of human laughter. Neuroscientist Jaak Panksepp first discovered that rats laugh when they play. He initially believed that their play was silent. A student suggested using a transceiver to get a closer listen. The transceiver could lower high noises that humans are unable to hear. Panksepp found that while the rats played, they were making chirping sounds.
Panksepp wanted to know what the sound meant. There were many possibilities. It could mean joy, it could mean anger, or it could mean arousal. Panksepp experimented with tickling rats. He found they made the same noise as when they were playing together. He also found that the rats chased after his hand when he stopped tickling them. For Panksepp, it was clear as day. The chirping sounds meant the rats were having fun and didn’t want the fun to stop. This was laughter.
Panksepp acknowledges that not everyone agrees that laughter is the correct word for the noises that rats and other animals make. Dr. Davila-Ross describes it as expressions of joy. She has studied laughter in chimpanzees. Laughter in apes is most similar to human laughter. She believes this points to a common evolutionary ancestor. She says, “Based on the study, we can now say laughter is at least 30 million to 60 million years old.”
Many animals including meerkats, owls, dolphins, camels, and foxes have been recorded laughing. Most of the time this laughter is caused by tickling. What makes humans laugh is more complicated. According to one theory, reversing expectations is essential for many types of humor. While most animals lack the language to do this, Koko the sign language using gorilla is an exception. She can use over 1,000 signs and understands 2,000 English words. From time to time, she uses her language ability to crack jokes. She once laughed at her trainer’s clumsy movements after tying her shoelaces together and signing the word for “chase.” The book The Humor Code describes how Koko “plays with different meanings of the same word. When she was asked, ‘What can you think of that’s hard?’ the gorilla signed, ‘rock’ and ‘work.’”
Comedian Robin Williams once met the famous signing gorilla, and he left without any doubts about whether animals laugh. He says, “I recently had a mind-altering experience communicating with a gorilla. Her name is Koko. We shared something extraordinary. Laughter.”