Laughter in animals

Laughter in animals
Laughter might not be confined or unique to humans, despite Aristotle's observation that "only the human animal laughs". The differences between chimpanzee and human laughter may be the result of adaptations that have evolved to enable human speech. However, some behavioural psychologists argue that self-awareness of one's situation, or the ability to identify with somebody else's predicament, are prerequisites for laughter, so animals are not really laughing in the same way that we do.

Research of laughter in animals may identify new molocules to alleviate depression, disorders of excessive exuberance such as mania and ADHD, or addictive urges and mood imbalances.

Non-human primates
Chimpanzees, gorillas, and orangutans show laughter-like vocalizations in response to physical contact, such as wrestling, play chasing, or tickling. This is documented in wild and captive chimpanzees. Chimpanzee laughter is not readily recognizable to humans as such, because it is generated by alternating inhalations and exhalations that sound more like breathing and panting. The differences between chimpanzee and human laughter may be the result of adaptations that have evolved to enable human speech. There are instances in which non-human primates have been reported to have expressed joy. One study analyzed and recorded sounds made by human babies and bonobos also known as pygmy chimpanzees were tickled. t found although the bonobo’s laugh was a higher frequency, the laugh followed the same spectrographic pattern of human babies to include as similar facial expressions. Humans and chimpanzees share similar ticklish areas of the body such as the armpits and belly. The enjoyment of tickling in chimpanzees does not diminish with age. Discovery 2003A chimpanzee laughter sample. Goodall 1968 & Parr 2005



Rats
It has been discovered that rats emit short, high frequency, ultrasonic, socially induced vocalization during rough and tumble play, and when tickled. The vocalization is described a distinct “chirping”. Humans cannot hear the "chirping" without special equipment. It was also discovered that like humans, rats have "tickle skin". These are certain areas of the body that generate more laughter response than other. The laughter is associated with positive emotional feelings and social bonding occurs with the human tickler, resulting in the rats becoming conditioned to seek the tickling. Additional responses to the tickling were those that laughed the most also played the most, and those that laughed the most preferred to spend more time with other laughing rats. This suggests a social preference to other rats exhibiting similar responses. However, as the rats age, there does appear to be a decline in the tendency to laugh and respond to tickle skin. The initial goal of Jaak Panksepp and Jeff Burgdorf’s research was to track the biological origins of joyful and social processes of the brain by comparing rats and their relationship to the joy and laughter commonly experienced by children in social play. Although, the research was unable to prove rats have a sense of humor, it did indicate that they can laugh and express joy. Panksepp & Burgdorf 2003 Chirping by rats is also reported in additional studies by Brain Knutson of the Natiional Institutes of Health. Rats chirp when wrestling one another, before receiving morphine, or having sex. The sound has been interpreted as an expectation of something rewarding. Science News 2001

Dogs
The dog-laugh sounds similar to a normal pant. However by analyzing the pant using a spectrograph, this pant varies with bursts of frequencies, resulting in a laugh. When this recorded dog-laugh vocalization is played to dogs in a shelter setting, it can initiate play, promote pro-social behavior, and decrease stress levels. In a study by Simonet, Versteeg, and Storie, one hundred and twenty subject dogs residing in a mid-size county animal shelter were observed. Dogs ranging from 4 months to 10 years of age were compared with and without exposure to a dog-laugh recording. The stress behaviors measured included panting, growling, salivating, pacing, barking, cowering, lunging, play-bows, sitting, orienting and lying down. The study resulted in positive findings when exposed to the dog laughing resulted in the following:  significantly reduced stress behaviors, increased tail wagging and the display of a play-face when playing was initiated, and the increase of pro-social behavior such as approaching and lip licking were more frequent. This research suggests exposure to dog-laugh vocalizations can calm and possibly increase shelter adoptions. Simonet, Versteeg, & Storie 2005 A dog laughter sample. Simonet 2005