Re: Why don't animals laugh?

The brief answer to your question is that other animals do laugh. The 
following is a brief excerpt from an article that appeared in “American 
Scientist” which describes laughter in chimpanzees:

Laughter 
Chimpanzee Laughter

"There is a common misperception that laughter is exclusive to human 
beings. From at least the time of Darwin, however, it has been known that 
chimpanzees and other great apes perform a laugh-like vocalization when 
tickled or during play. To pursue the details of this primate laughter, I 
teamed up with Kim Bard, who is nursery director and caregiver for young 
chimpanzees at the Yerkes Regional Primate Center in Atlanta. It is a 
pleasure to be able to play with young chimpanzees in the pursuit of 
one's science. Chimpanzee (Pan troglodytes) laughter differs in many ways 
from its human counterpart. The vowel-like notes of human laughter are 
performed by chopping a single expiration, whereas chimpanzee laughter is 
a breathy panting vocalization that is produced during each brief 
expiration and inspiration. Unlike human laughter, the laughter of a 
chimpanzee lacks discrete, vowel-like notes that have sharp leading and 
trailing edges on sound spectra. Chimpanzee laughter has the sound and 
cadence of a handsaw cutting wood. The sounds of chimpanzee and human 
laughter are sufficiently different that without viewing the 
characteristic "play face" and source of stimulation (such as play and 
tickle), naive human beings may be unable to identify the chimpanzee 
vocalization as laughter. You can experience the difference in production 
between the two forms of laughter by placing a hand on your abdomen and 
comparing the abdominal pulsations of chimpanzee-like panting with the 
smoother act of speaking "ha-ha-ha" during a single expiration."

Hope this helps,
Gabriel Vargas md/phd




References:
American Scientist Online “Laughter” http://www.americanscientist.org/template/AssetDetail/assetid/2459
1/page/3