I think a cornerstone of panpsychism is that none of the concepts presently available to any physicalist explanation is sufficient or on the horizon, therefore it is necessary to entertain such ideas as a universe-spanning proto-consciousness.
I find this position to be pre-emptive, not in the spirit of scientific open mindedness, not compatible with any research program that could prove or disprove it, and completely emptyhanded in any conversation that seeks to understand consciousness in functional or structural terms as well as completely emptyhanded in even beginning to explain the combination problem.
Until it gets its act together and gets out of alpha-testing, I fault pansychism proponents for bringing a "teach the controversy" approach to a table of scientific investigation at which they are yet to have earned a seat.
However, my understanding of the double slit experiment is that the "observer" in the experiment means something more like measurer or measurability, which can be done by devices. And it shouldn't be construed as being deeply tied to consciousness in philosophically important sense.
So when I say like the double slit needs to be adapted, it would need to account for such. It would need to test for 'choice' from a particle... somehow...
Or... maybe randomness as a concept is flawed. Maybe randomness === '(some level of informed?) choice' from particles we are not privy too. not some 'hidden variable' but a dynamic ability to 'choose'?
How would we prove random is random and not a choice/decision we can't see or understand?
We might as well posit pancandleness in order to explain the candleness of candles. Without such a thing, why call a candle a candle? It would merely be just a temporary arrangement of molecules.
Likewise, a feeling of red isn't due to some mysterious redness. It is just the label we put on a particular configuration of neural activation. No need to make it mysterious until someone shows that more is required to explain it.
Well... that's the problem no one can 'show' it, but we all know the feeling of 'redness'(mysterious or not, caused by neural activations alone or not) is still fundamentally different from the knowledge that red light is shining on another object. And that's the problem.
I mean, maybe you don't experience this feeling and I'm truly talking to an automaton (hello!). But I can't honestly take these claims seriously when it's extremely obvious to me that the feeling of seeing red is fundamentally different from the pure information content that red light is shining on my face. It's a fundamental feeling of sensation that is simply inexplicable.
Why does red feel anything at all. Why is there a conscious (whatever that even is) experience of red. Wouldn't the universe work fine if it's all just automata (however intelligent). Why is there a feeling of existence at all. Is that necessary for the universe. Why? Waving these questions away as 'not mysterious' is either due to laziness or a fundamental difference in experience (which would be fascinating on its own, but I have no idea how to approach methodologicaly).