The argument is just a little circular, isn't it? The Piraha ignore colors and numbers, they lack words for colors and numbers, so the lack of words must be cau

The argument is just a little circular, isn't it? The Piraha ignore colors and numbers, they lack words for colors and numbers, so the lack of words must be causing their general ignorance of colors and numbers. It could be the other way round - people tend to come up with words (or terms) for anything of interest to them. For example, linguists might come up with a terms like "linguistic relativity" or "Sapir–Whorf hypothesis" for the suspicion that linguistics drives thought. It does ignore a very common principle of linguistics - that language is flexible. If you don't have a word, people tend to invent one.