An important review article by Josep Call has appeared in the February issue of Mind and Language bearing the straightforward title, “How Artificial Communication Affects the Communication and Cognition of the Great Apes.” The title suggests an important question for this blog: how much did the human lineage change just by the fact that it had begun speaking? We today have a variety of differences between ourselves and apes. How many of those traits can be attributed to the fact that we speak, and how many required other evolutionary interventions?
Much of the paper takes the form of presenting evidence of an interesting change, and then undercutting it with the conclusion that there is less here than meets the eye. For example, if you present chimpanzees with two bowls of food, one large, one smaller, the chimpanzee will immediately reach for the larger amount of food. If you put a clear plastic barrier between the chimpanzees and the food, it will still reach for the larger. Suppose that you now complicate the chimp’s life. It reaches for the larger bowl on the other side of a barrier, and you hand it the smaller bowl. It turns out to be very difficult for a chimpanzee to learn to reach for the smaller bowl to get the bigger bowl. However, a chimpanzee can learn numbers and know, for example, that 6 is a bigger amount than 4. Once having learned the numbers, it can learn to reach for the smaller number to get the larger bowl. This work suggests that replacing a perception with a symbol liberates the animal’s thought processes by putting a little distance between what you see and what you want.
Such a tidy conclusion is welcome, but Call immediately goes on to undermine the idea by saying that other experimental designs have found ways where the chimpanzee can learn to reach for the smaller. He adds that even with the original design, they learn the task if allowed more trials. Finally, he notes that there is a great deal of individual difference and some individuals learn the solution quickly. Thus, the ultimate conclusion is much less tidy. Using symbols does seem to free up the animal’s thinking a bit, but the change appears to be a matter of degree rather than introducing a new trait.
Josep Call works with Michael Tomasello at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany and is in general agreement with Tomasello (and this blog) in holding that apes do not have the cooperative motivations that humans do, and their motivation does not change as a result of learning to speak. Call does investigate this question. He reports:
There is considerable evidence, and it continues to accumulate, that enculturated apes outperform non-enculturated apes in several domains including social learning, communication, and more recently, tool-use. However, what changes in enculturated animals is unclear. 
“Enculturated” seems to refer to captive apes that interact with sympathetic humans for their survival. Fifteen years ago Call and Tomasello co-authored a paper in which they argued the critical novelty in the enculturated environment was that humans treated apes as “intentional beings,” individuals with their own wants and purposes, and that this treatment “may lead to a fundamental change in the social cognition of apes such that they begin, … to view others as intentional agents” [11 quoting p. 394]. New data, however, has led Call and Tomasello to change their mind. They now believe that “all apes, not just enculturated ones, know about essential aspects of intentional action and can attribute goals to others” .
Again, the change seems to be one of degree rather than introducing a novelty. Call suggests that the reason behind the intellectual improvement among the enculturated apes is that they have learned to pay attention to things that non-enculturated apes ignore. Naturally, this blog likes attention-based explanations, but we will have to wait to see how it holds up.
A starlit sentence late in the paper gets the key point: More than transforming the mind, symbols reveal its richness . Call goes on to argue that “a complex cognitive system, like that possessed by apes and other animals, can find new solutions to new problems by virtue of its flexibility” . Thus, the changes that follow the introduction of symbolic communication may reflect a response to the more complex environment rather than the introduction of symbols themselves.
Our hypothesis is that when subjects are exposed to new challenges and opportunities early in their ontogeny, they develop solutions taking those new elements into consideration and in doing so come to differ from their conspecifics that did not face the same physical and social environment during their ontogeny. 
That’s a fancy way of saying that, even among the apes, an enriched childhood leads to a richer life. It would be charming if we could say that the introduction of symbols and life among the humans transform the ape mind, but Call concludes that although the ape mind can be enhanced, “no mental revolution takes place” .
For this blog the implication is clear. Speech alone is not the only distinguishing intellectual feature between humans and apes. Even if you got apes to cooperate enough to speak, something more would be necessary before they became us.