There is a species of primate in South America more gregarious than most other mammals, with a curious behavior.The members of this species often gather in groups, large and small, and in the course of their mutual chattering , under a wide variety of circumstances, they are induced to engage in bouts of involuntary, convulsive respiration, a sort of loud, helpless, mutually reinforcing group panting that sometimes is so severe as to incapacitate them. Far from being aversive,however, these attacks seem to be sought out by most members of the species, some of whom even appear to be addicted to them....the species in Homo sapiens (which does indeed inhabit South America, among other places), and the behavior is laughter.