Yes, I should have been more clear that what I meant was that this is one possible alternative explanation that hasn't been ruled out by the experiments done, n

Yes, I should have been more clear that what I meant was that this is one possible alternative explanation that hasn't been ruled out by the experiments done, not that this is the only possibility. I had said "could have been consciously or subconsciously prompting her" and should have also said "could have been using their own theories of mind and inference ability to read more into Koko's actions than what is really there." I was just trying to list one more possible explanation that the experiments hadn't ruled out, not cover everything, but you're right, those are each also possibilities.