I wanted to finish this summary on the weekend but just didn't get round to it because I've got a lot to do right now. Here it is anyway:
Like I said in my last post, the rest of Chapter 2 focuses on what in the chimpanzee/human lineage provided a basis for modern language.
One crucial factor is chimpanzees' ability to use and comprehend pointing.
In the wild, chimpanzee pointing is very rare. But approximately 60 to 70 percent of all captive chimps spontaneously use pointing in an imperative manner in their interactions with humans, e.g. by pointing to food that is out of reach as a request for the human to get it. But pointing gestures that aren't imperative are virtually absent. This even applies to language-trained apes such as Kanzi. In the few studies that have been done on this, 96-98 percent of all their pointing were imperative. The other 2-4 had no clear function.
Thus there is nothing in chimpanzees' pointing behavior that would suggest that they are capable of or interested in sharing attention within a joint attentional frame.
On the other hand, in a Brain Science Podcast interview, Stuart Shankar, co-author of The First Idea: How Symbols, Language, and Intelligence Evolved From Our Primate Ancestors to Modern Humans , reports of a an encounter he had with the bonobo Panbanisha in which she showed him various plants and classified them, for example, as poisonous. Shankar interprets this as truly sharing attention and informing for the the sake of informing, but Tomasello argues that these kinds of gestures are not to be seen as as truly declarative or informative, as they are more
„recognitory or classificatory, as the ape simply recognizes something and produces the associated sign in recognition“ (Tomasello 2008: 38).
Interestingly, chimpanzees are much worse comprehending other people's pointing than they are producing it themselves.
In a cool experiment, Tomasello and his colleagues have shown that in a cooperative situation, chimpanzees are unable to grasp the fact that the hidden food is in the bucket that the experimenter is pointing to. Human infants, on the other hand, are able to understand this task by 14 months of age. (Behne et al. 2005) In a competitive version of this task, however, chimpanzees fare much better (Hare & Tomasello 2005). These results suggest that chimpanzees have problems with "shared intentionality," i.e. recognizing situations where you have shared cooperative goals with others and have the same shared attentional frame.
Intentionality & Perception
According to Tomasello, apes and young human children both attribute simple forms of intentionality to other actors. For example, when a human repeatedly tries to give food to a chimpanzee but fails because he is clumsy, the chimp reacts patiently, whereas he gets frustrated when the human is failing to pass him the food for no good reason or because of unwillingness.
Most of the time enculturated chimpanzees also imitate
“demonstrator’s action more often when he freely chose his action than when he was forced to use it by some constraint” (Buttelman et al. 2007: F37, see here).
Crucially, chimpanzees also understand that others have perceptions and see things. In a competitive task with a dominant chimpanzee, for example, subordinate chimps, secretly take a food reward when the other one is unable to see him, but not when the food can be seen by the dominant chimp.
According to Tomasello then,
"The overall conclusion is thus that apes understand others in terms of their goals and perceptions and how these work to determine behavioral decisions, that is, they understand others as intentional, perhaps even rational, agents (Tomasello 2008: 4)Intentionality + gestural fexibility = evolutionary foundations of language ?
This seems to be the conclusion Tomasello draws at the end of the second chapter. Clearly, when a chimpanzee produces a gesture, he does this in a very flexible manner that even shows sensitivity to the attention of the other. Ape vocalizations on the other hand are mostly inflexible and do not take into account the presence or absence of attention to the displays. Thus there is strong evidence that the capacities apes display in the gestural modality
"are the original font from wich the richness and complexities of human communication and language have flowed. " (Tomasello 2008: 55).
Behne, T., Carpenter, M., and Tomasello, M. (2005). One-year-olds comprehend the communicative intentions behind gestures in a hiding game. Developmental Science, 8, 492–499.
Buttelmann, D., Carpenter, M., Call, J., and Tomasello, M. (2007). Enculturated apes imitate rationally. Developmental Science, 10, F31– 38.
Hare, B., and Tomasello, M. (2004). Chimpanzees are more skillful in competitive than in co-operative cognitive tasks. Animal Behaviour, 68, 571–581.
Tomasello, Michael (2008): The Origins of Human Communication. Cambridge, MA; London, England: MIT Press.