So, in my intro to psych class, the topic of Koko the Amazing Signing Gorilla! came up. I seem to remember that there were a lot of flaws in the way the experiment was done - lack of repeatability, lack of external verification, confirmation bias, researchers who don't sign fluently, etc. Can anyone point me towards sources for this? Preferably from a Deaf point of view, and preferably relatively 'official' (or scholarly, even).