Laughter in animals

Laughter in animals other than humans describes animal behavior which resembles human laughter. Several non-human species demonstrate vocalizations that sound similar to human laughter. A significant proportion of these species are mammals, which suggests that the neurological functions occurred early in the process of mammalian evolution. Laughter as communication is found in over 60 species. Chimpanzees, gorillas and orangutans show laughter-like vocalizations in response to physical contact such as wrestling, play chasing or tickling. This behavior is documented in both 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. It sounds similar to screeching. The differences between chimpanzee and human laughter may be the result of adaptations that have evolved to enable human speech. One study analyzed sounds made by human babies and bonobos when tickled. It found that although the bonobo's laugh was a higher frequency, the laugh followed the same sonographic 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. Research has noted the similarity in forms of laughter among humans and apes (chimpanzees, gorillas and orangutans) when tickled, suggesting that laughter derived from a common origin among primate species, and therefore evolved prior to the origin of humans. Rats emit long, 50-kHz ultrasonic calls that are induced during rough and tumble play, and when tickled by humans. The vocalization is described as distinct "chirping". Like humans, rats have "tickle skin", areas of the body that generate greater laughter responses than others. Rats that laugh the most also play the most and prefer to spend more time with other laughing rats.