How many ways can a human laugh?

[People] can chortle, chuckle, titter, hoot, giggle, snigger, howl, or guffaw. This richness of language may suggest to some that laughter, itself, is a phenomenon of infinite variety, one that lends itself to endless subcategorisation…. [W]ork led by Roza Kamiloglu, a psychologist at the Free University of Amsterdam, provides evidence that there are just two primary types of laughter: one generated when people find something funny and one that can be induced only through the physical act of tickling.

The findings … are more than light entertainment. They could, instead, point scientists towards the evolutionary roots of laughter…. One of the first things that infants do early in life is laugh. Even babies born deaf spontaneously produce laughter.

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As for all the other forms of laughter that … people produce, these probably evolved millions of years after tickling came along, when the human brain became complex enough to understand irony, slapstick and puns. But he who laughs last, it would seem, laughs longest.

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