I'm looking to describe an effect caused by using a particular construction in English, and the fact that it affects the listener and the whole of their thought processes without the listener being aware of it. The words insidious or pernicious would almost do, but these have negative connotations. The effect here is neither positive or negative.
The use of (x) has a(n) _____ effect on our mental processes.
That sentence requires an adjective, but an adverb would do just as well :
The use of (x) affects our mental processes _____ .
So, a quick recap. Ideally the word would:
- convey that the process is silent and unnoticed by the speaker
- convey that it spreads through and affects all of the speaker's thought processes
- not have any particularly negative or positive connotation