The analogy I've used with friends is that neurotransmitters are to brain communication as letters are to language. If something gives you "more E" or "less L"

The analogy I've used with friends is that neurotransmitters are to brain communication as letters are to language. If something gives you "more E" or "less L" in your writing, the change in letter frequencies is probably not the thing that's directly making your sentences better, but the change shows it's clearly making a difference. There is an effect that is occurring on a level of complexity that we just can't fully decipher yet.