I think Koko's trainer really did believe her more extravagant claims. So did Clever Hans's. But there was a lot of wishful thinking along the lines of "Koko's

I think Koko's trainer really did believe her more extravagant claims. So did Clever Hans's. But there was a lot of wishful thinking along the lines of "Koko's making a weird gorilla joke that doesn't make sense to human minds" when a more likely explanation would be "Koko really doesn't know what she is saying".