I have nothing against splitting infinitives, but "to once they have terms for something take for granted" is pretty extreme. It's likely to overflow the reader's stack. After fixing that, running an iteration of the "omit needless words" algorithm, and doing a bit of rephrasing, here's what I came up with:

There's a related problem: If they have terms for something, humans tend to think things that make syntactic sense actually have semantics behind them.

(Ninja edit: Some more needless words omitted, including a nominalization.)

(Edit 2: Here's a better nominalization link because it gives examples of when to use nominalizations, not just when not to use them.)