Why do people slap their knees (laps) at a funny joke? When I hear or see something incredibly funny, I will certainly look to slap my lap. But why? Is there a primitive mechanism at work here? Something, perhaps, to do with evolution? What does hitting something (yourself) accomplish?
Also, when someone tells me a joke while I am in the middle of eating or drinking, I may start to laugh, but have to swallow my food first. I have noticed I get significantly less enjoyment out of the joke when I am finally able to laugh again. Likewise, when I tell a joke to other people in the same circumstance (they are eating or drinking) I feel like it’s a wasted opportunity. When they are able to laugh again, it’s usually very little, and the humorous moment is gone.
Why do people slap their knees (laps) at a funny joke? When I hear or see something incredibly funny, I will certainly look to slap my lap. But why? Is there a primitive mechanism at work here?
I suspect that “knee slapping” is more cultural than DNA. Do Aborigines slap their knees?
What does hitting something (yourself) accomplish?
One element of humor is “surprise” and it’s not uncommon for a surprise to evoke a physical response - fight or flight and all that. In other words, a surprise can make you jump and it’s not hard to see how that jump and be morphed into a harmless knee slap as a way to dissipate that physical response. One way of looking at it would be that people slap their knee as a coping mechanism for dealing with the stress of the surprise.
The humorous moment passes and you don’t laugh as much anymore because the sudden flash of “getting it” is what makes you laugh in the first place. Otherwise, you could read over the same jokes you had just heard, and crack up all over again.
Learned behavior. The only time I’ve seen someone in Spain (actually, in Western Europe) do something which could remotely be called “slap their knees laughing” it was an actor in a comedy; for some it’s almost a signature move. I’ve sometimes see people grab their thighs (sometimes right above the knee) because laughing had made them lose their breath: that’s an “out of breath” gesture. And as for “slap” your belly, I’m confused. Grab it because it’s hurting from laughing so much, yes. But slap it, color me confused. Maybe what the OP calls a slap I’d call a quick grab.