[komali2]

I swear I saw a paper on here a couple months back about some weird negative correlation between intelligence and tendency to breath through the mouth rather than nostrils. Like, somebody had managed to provide evidence that mouth-breathers are stupid.

[stagbeetle]

Air is processed differently (see: less "goodly") when taken in by mouth.

It's not too much of a stretch this could affect cognition the same way pollution does.