I don't think that sentence would get added complexity. "adopted child" will likely be a 7-8 letter word using the same root as stepfather. Stepfather is a word that you can't derive from knowing "adoption" which make things harder for the language speaker. You can't derive spouse from knowing the word marriage.
I'm working on a conlang (constructed language) and would like some input from the Less Wrong community. One of the goals is to investigate the old Sapir-Whorf hypothesis regarding language affecting cognition. Does anyone here have any ideas regarding linguistic mechanisms that would encourage more rational thinking, apart from those that are present in the oft-discussed conlangs e-prime, loglan, and its offshoot lojban? Or perhaps mechanisms that are used in one of those conlangs, but might be buried too deeply for a person such as myself, who only has superficial knowledge about them, to have recognized? Any input is welcomed, from other conlangs to crazy ideas.