Anecdatum but I experienced looped cognition on a peculiar combination of substances.

I was able to treat thoughts as solid objects and manipulate them iteratively. (Ordinarily they're more like "glimpses" or "flashes" that fade rapidly. So I guess it would be like the mental equivalent of tracers.)

I was able to stack thoughts on top of each other, like planks. (I can do something similar or the narrowly but the planks are not nearly as wide!)

I didn't do any tests unfortunately but subjectively my cognition was greatly enhanced. (Spent a few years catching up with the insights I had that evening.)

Might be unrelated, but the part about "looped transformers" made me wonder if there's a similar "stepwise" increment going on here.

Edit: Okay, 6.8-18% is slightly less dramatic than what I was referring to.