In honor of the recent April Fools Day, let us look at a humorous subject: the laughing dog.
Many a dog owner has sworn that their dog is smiling at them or laughing along with them. Certainly, the opened-mouthed expression on the face of a panting, playing dog looks like a smile. But zoologists warn us about anthropomorphizing animals, reading human meanings into their actions or expressions. Often people will see what they want to see, regardless of the real meaning of the animals' actions.
Yet intriguingly there is a new report in the journal Science that speculates that "play sounds" in animals, like panting sounds in dogs and chimps that resemble human laughs, do indeed represent an animal equivalent of laughter. Chimps display the laughter-like panting noises when they chase or tickle each other. Anyone who has roughhoused with a dog has heard their "play pants" as they chase and tumble.
The author of the report is Dr. Jaak Panksepp, of Bowling Green State University in Ohio, who studies the neuroanatomical and neurochemical mechanisms of emotional behaviors in the emerging field of affective neuroscience. Dr. Panksepp's work seeks to understand a variety of emotional responses including social bonding and social play, and how these affective responses are organized in the brain. In a recent issue of the journal Science, Dr. Panksepp cited the long observed panting "play noises" of chimpanzees, which sound like human laughter, and panting sounds of dogs at play.
In a 1998 study, Panksepp and another researcher reported that rats produced a high-pitched chirping sound during play, and that the sounds were associated with a pleasurable response to tickling or play. When rats are tickled in a playful way, they become socially bonded to humans and even would seek out tickles. The rats' chirps do not sound like human laughter and are even beyond our hearing range, yet are associated with play.
Neural circuits in the brain that release the neurotransmitter dopamine light up in the human brain when people laugh. A similar response is thought to occur in rat brains during the chirping response.
Research shows that our laughter circuits are found in the more primitive parts of our brain, in structures that we share with many animals. This suggests that the capacity for human laughter preceded the capacity for speech, according to Panksepp. Laughter is a universal human expression that needs no translation across cultures, although jokes provoking laughter might. Babies learn to laugh spontaneously at about three months, long before they learn to talk.
Human laughter is an emotional response that is not entirely in our control. It is surprisingly hard to fake a laugh and easy to detect a fake one. Yet they erupt spontaneously in the right circumstances. Although we often think of laughter in response to humor, research shows that it is a social response that is more likely linked to social bonding than to what is funny. People rarely laugh alone, and the laughter of others is likely to provoke us to laugh, suggesting a connection to another universal human social behavior, smiling.
Studies in humans indicate that laughter may have more to do with social bonding, or with communicating to others that one is only playing, than with amusement. This social communication aspect may be the common link with animal play sounds, as they may communicate that no harm is intended.
However, making jokes might still be a purely human trait.
While many scientists are skeptical of the concept of animal laughter, the link between play sounds and ancient parts of the brain that we share with many animals raise an intriguing, even amusing, thought. If animals engage in play, why can't they laugh too?
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