Years ago I had a conversation with my brother, when his son was a few months old. At some point I mentioned something along the lines of "he [the infant] thinks such-and-such", and he countered with "he doesn't think, he doesn't have any language".

It's unlikely that this statement was informed on any sort of linguistic basis, as he's not the kind of person who would read such things (he's more of the artsy type, not the "hacker" type), it was just intuitive to him. I think it is for many people, including me, but the human sense of "intuition" on these things is not always equally accurate.

This is kind of similar to how many people have an intuitive sense of dualism, that the mind and body are two separate things. This concept is highly unlikely, but for almost everyone – myself included – it's very natural, hence the gazillion stories about people swapping bodies and whatnot.