An outlandish animal

Ludwig Wittgenstein c. 1948 (from Culture and Value (ed. G. H. Von Wright with Heikki Nyman, trans. Peter Winch):

Two people are laughing together, say at a joke. One of them has used certain somewhat unusual words and now they both break out into a sort of bleating. That might appear very extraordinary to a visitor coming from quite a different environment. Whereas we find it completely reasonable.

(I recently witnessed this scene on a bus and was able to think myself into the position of someone to whom this would be unfamiliar. From that point of view it struck me as quite irrational, like the responses of an outlandish animal.)