Earlier quoted context omitted.
I think you're confusing cognitive processes with neurological processes. Of course we can reflect on actual cognitive processes such as forgetting or learning, and of course psychologists can gather evidence on these cognitive processes. What we cannot do is make definitive claims about neurological processes and structures based on what we know about our cognitive processes.
> Of course we can reflect on actual cognitive processes such as forgetting or learning Is there any actual evidence that our so-called reflections on our own thinking are anything more than hallucinations? "It's obvious" doesn't count as evidence.
These studies confirm our perception that we can forget stuff.