We are not monkeys. There are many facets of our sentiency that differentiate us from the gorillas, orang-utans, baboons and chimpanzees: Language, exploration, the desire for self-understanding, historical perspective, and the interest in what happens after death.
How much does laughter belong solely to sentiency? It is believed by some zoologists that gorillas laugh when tickled. (Gorillas also understand anger and can sulk and bear grudges and such behaviour is not considered sensible behaviour for humans; it is seen, rightly, as aberations.)
The "laughter" of gorillas when tickled, and that of humans when tickled, is merely a physical reaction, not a cerebal reaction. It is not related to the laughter that we experience as a result of a cerebal event.
Cerebal laughter-inducing events include those of language and those of physical activity. In both scenarios it is the perversion of what is considered the norm, a norm that differs hugely in different cultures, that illicits the laughter. This laughter is entirely an effect of a mental process infused with the intelligence and experience of the laughee. Therefore, it is wholly sentient.
Laughter is a sentient process that is impossible for any other animal to produce.
Respect laughter in the same way that you respect your use of language, the advances of science, the great feats of exploration on earth and beyond. Laugh when an event occurs that deserves such a response. Do not just laugh for no reason.