And in it the author (who spent decades working with and teaching chimps) concludes that chimps have the intelligence to talk but not the vocal chords. They can understand humans talking (in the same way that a dog can understand verbal commands) but they cannot do much besides grunt or hoot back.
However when you change the conversation method to something else (such as sign languge) chimps can talk back exceedingly well. In the book mentioned above the author has video proof that the chimps can talk to humans (and each other) at the level of a two to four year old child.
This is the main chimp in the book:
This doesn't seem to just apply to chimps either. Gorillas (and other large apes) can do the same.
See for example this article regarding the work of Francine Patterson with Koko:
On the Evidence for Linguistic Abilities in Signing Apes
From which I quote (since it's Elsevier-walled):
>> One of the major problems with Patterson's study is that it presents very little data. While several large corpora of the utterances of children have been published (e.g. Bloom, 1973), there is as yet no corpus of any ape's signing behavior. That is, Patterson fails to provide a substantial number of transcribed utterances. Rather, she relies upon individual examples to support her interpretations. In the absence of a corpus of utterances, however, these examples are impossible to interpret. One cannot determine whether they have the functions wich Patterson attributes to them, or whether they resulted from the ape acting as a "random sign generator" which happened to emit sequences that could be selectively chosen to illustrate particular points. This sampling problem vitiates Patterson's claim that certain combinations demonstrated that Koko possessed the ability to creatively combine signs into novel utterances. Those who assert that apes have shown linguistic abilities have invariably relied upon examples such as Washoe's signing water bird for duck. In the absence of a large corpus, however, these examples are subject to multiple interpretations. Patterson's claim that cookie rock was a creative description of a stale sweet roll loses much of its force if Koko also produced utterances such as cookie tickle, cookie hat, and toothbrush cookie in similar contexts. The largest corpus of utterances from any signing ape, that of Terrace, Pettito and Bever (1967a,b) shows that their subject, a chimpanzee named Nim Chimpsky, did in fact combine each vocabulary sign with a large number of other signs. Although each of the resulting combinations could be interpreted metaphorically, a simpler interpretation is that he merely combined signs randomly. The correct interpretation depends on other information--an accounting of the frequencies with which signs occurred in combination with one another, the contexts in which combinations occurred, the content of the teachers' signing--which Patterson fails to provide. Without this information, the importance of her examples cannot be ascertained.
>> Patterson's discussion of her cookie rock example provides some measure of this problem. She states, "Although Koko has produced uninterpretable strings (as do some children), most of her utterances are appropriate to the situation and some are strikingly apt" (p. 88). She then cites some "interpretable" examples, including cookie rock; the "uninterpretable" strings are not described. It is the case that only "interpretable" sequences are ever documented in the reports on ape signing. Only by presenting an unedited corpus of responses, however, could Patterson's assertion be validated.
Note also that one of the two authors in the quoted paper is Laura A. Pettito, one of the researchers that worked with Nim Chimpsky.
I think you might be overreaching here! Roger Fouts was (and still is) an expert and I fear you may just be regurgitating information from a study that is nearly forty years old.
The book I mentioned earlier was written twenty years after the linked article and explicitly mentions the bias he experienced in an entire chapter alone. It counters and logically explains away a lot of the conclusions that they falsely arrived at. If I remember correctly one of the main reasons that studies in the 70s and 80s liked to play down the intelligence of chimps is that it allowed the "for profit" chimp research centers to continue operating. A lot of these studies were published and financed by people who would lose out if they had to provide better (and therefore more costly) conditions for their "dumb testing subjects".
As for the clever hans effect, Roger was extremely careful to not to selectively extract words and interpret them during his research. He even invited officials from the ASL institute to verify his findings first hand.
The clever hans effect also cannot explain away why chimps started signing to each other (when no humans were present and the chimps were being monitored by video) or why sometimes the chimps would sign to themselves (much in the same way that humans occasionally mumble to themselves).
I implore you (if you have the time) to read Roger's book. It really is an eye opener and very well written!
In any case, the article is old because the research it refers to is old and that research is old because the majority of interested scientists consider the question about great apes' language answered, and in the negative. A few holdouts, of course, will always refuse to give up their preferred theories. That doesn't mean they're right.
>> The clever hans effect also cannot explain away why chimps started signing to each other (when no humans were present and the chimps were being monitored by video) or why sometimes the chimps would sign to themselves (much in the same way that humans occasionally mumble to themselves).
Sure, but there's nothing stopping the apes from signing to each other, or to themselves, at random, without the signing actually meaning anything.
The point of the article I cite is that there is no way to know that because of the shoddy methodology followed in most such experiments.
As to the Clever Hans effect, this is what Noam Chomsky has to say:
>> CHOMSKY: Interesting story about poor Nim. The experiment was carried out by a very serious experimental psychologist, Herbert Terrace. A convinced Skinnerian [student of Behaviorist, B.F Skinner], he expected that if an ape was brought up just like a human it would be a little human. He had some very fine assistants, including some excellent former students of ours, and others who went on to be leading figures in the field. The experimentation was done with meticulous care. There’s a book, called Nim, which describes it, with great enthusiasm, claiming at the end that it was a grand success and the ape is ready to go on to great things. Then comes the epilogue. When the experiment was over, a grad student working on a thesis did a frame-by-frame analysis of the training, and found that the ape was no dope. If he wanted a banana, he’d produce a sequence of irrelevant signs and throw in the sign for banana randomly, figuring that he’d brainwashed the experimenters sufficiently so that they’d think he was saying “give me a banana.” And he was able to pick out subtle motions by which the experimenters indicated what they’d hope he’d do. Final result? Exactly what any sane biologist would have assumed: zero.
Another commenter in the parent thread also posted a link to a video where Chomsky discusses the Clever Hans effect in the Nim Chimpsky research in more detail.
>> If I remember correctly one of the main reasons that studies in the 70s and 80s liked to play down the intelligence of chimps is that it allowed the "for profit" chimp research centers to continue operating. A lot of these studies were published and financed by people who would lose out if they had to provide better (and therefore more costly) conditions for their "dumb testing subjects".
Those are very strong allegations of scientific misconduct, which of course we're not going to resolve on HN. However, I note that the people who published great ape language studies would benefit even more financially if they had managed to show that great apes can learn sign language.
In fact, the amount of money one would imagine them making would positively dwarf any expenses to improve the conditions of their subjects.
Anyway, sorry you don't want to continue the conversation.