Can we draw a line what is out of scope here and better refer to Cognitive Science?
P.s.: I started a similar topic on Cognitive Science.
I don't think it's productive to fret over putting every question in the right bucket. When a cog-sci oriented question is asked here, we should evaluate it the same way we did before that site was created. If it doesn't fit here, we then have a separate decision of whether it should be migrated or simply closed. (Of course, the same applies to UX oriented questions on Cognitive Science.)
My feeling is that there is a division between the sites in most cases, because UX should relate to application design questions ( in a very broad way ) whereas CS should handle scientific or theoretical questions.
In my time here, I think there have been a few - very few - questions that really overlap. What is probably more useful is for members here who have interest or knowledge to join CS, and vv, so that UX questions can also have CS insights, and CS questions can, where relevant, also have UX insights.