What is unpleasant and threatens my modesty is that in fact I am every name in history.
Nietzsche wrote that in a letter to Jacob Burckhardt in January, 1889, after his descent into insanity, but if you look past the self-absorption, in a disturbing and poetic fashion the sentence manages to captures the essence of the hypothesis that Tomasello defends in The Cultural Origins of Human Cognition: our uniquely human cognitive abilities exist because our minds "stand on the shoulders of giants," or contain within them the advances of the human minds that came before us. In Chapter 1, Tomasello puts forth this hypothesis, the basic reasons he thinks it is necessary (the "problem"), and in a very general way, the themes that will guide his defense of it. As Tomasello himself notes, Chapter 1 thus serves as a précis for the rest of the book. That means that it's important that we understand the basic concepts in the chapter, and also that we can begin to see some of the potential problems with Tomasello's view. In this post, I will briefly summarize the main points in Chapter 1, and describe one of the potential problems that may threaten the entire exercise.
In the beginning, Tomasello lays out the problem that motivates his hypothesis. Six million years ago, the evolutionary paths of modern apes and modern humans diverged. Until two million years ago, the evolutionary path of modern humans was dominated by one genus, Australopithecus, which was much more ape-like than human-like, particularly in its cognitive abilities. And it appears that most of our modern cognitive abilities arose within the last 250,000 years. Tomasello believes that this time period does not allow enough time for the evolution of these abilities through the ordinary mechanisms of biological evolution. Hence the problem: how can there be such large cognitive differences between apes and humans if there was not enough time for them to evolve through the ordinary biological evolution?
If there wasn't enough time for biological evolution to produce our uniquely human cognitive abilities through its ordinary mechanisms, then another mechanism is required, and Tomasello's hypothesis is that the mechanism through which most of our uniquely human cognitive abilities developed is cumulative cultural evolution. While other animal species are able to transmit information socially, they are not able to do so cumulatively, and therefore, as Blar notes in his first post on Tomasello, their inability to build on the past leaves them "doomed to repeat it." In Chapter 1, Tomasello gives us his hypothesis for how humans evolved the ability to transmit knowledge culturally. There are two primary parts to this hypothesis, one of which is responsible for the other: the ability to share attention with concspecifics, and the resulting development of uniquely human linguistic abilities. I'll briefly discuss each.
As Tomasello notes, humans and nonhuman animals share many of their basic cognitive skills. Tomasello lists perception, memory, attention, and categorization (p. 10) as shared cognitive abilities. He also notes that nonhuman primates, particularly those closest to us evolutionarily (chimpanzees and bonobos) are capable of innovation, or the creation of new knowledge and abilities (p. 5). But unlike humans, these nonhuman animals are unable to transmit their innovations to future generations. For Tomasello, there is one difference between humans and all nonhuman animals that allows us to develop the ability to transmit information cumulatively through culture (what he calls the ratchet effect). In order to do so, they must be able to understand that other humans have beliefs and intentions (p. 7-8). This understanding allows humans to reason about the actions of others, and this in turn allows us to imitate those actions intelligently. Thus the single difference between humans and nonhuman animals that evolved about a quarter of a million years ago must be one that makes this understanding possible. Tomasello's hypothesis is that this single evolved difference is the ability to identify with others of our species. This allows us to engage in "joint attentional activities," in which we recognize that another is attending to a specific object, and that he or she has beliefs and goals (intentions) that relate his or her actions to that object. This in turn allows us to imitate and learn from those actions. As we will see in later chapters, it also allows us to directly teach our knowledge and skills to others. In other words, once we are able to identify with other members of our species and engage in joint attentional activities with them, we are able to teach and learn collaboratively. According to Tomasello, it is these abilities that "form the basis for children's initial entry into the world of culture" (p. 7-8). Collaborative learning raises the human mind above the minds all of its evolutionary predecessors and all current nonhuman animals.
To illustrate this, Tomasello describes two examples that are missing one of two pieces of this puzzle. In the first example, autistic children are embedded in the "world of culture," but cannot enter it, because they lack the theory of mind abilities that allow us to identify with our conspecifics and thereby reason about their beliefs and intentions. This is why extremely autistic children display such profound deficits in uniquely human cognitive abilities, particularly language. In the second example, a child has the ability to identify with other humans, and thus to learn collaboratively, but grows up in an environment in which she is completely isolated from all other humans, and thus cannot benefit from the collaborative learning of accumulated cultural knowledge. This hypothetical child, Tomasello believes, will resemble the extremely autistic child in its cognitive abilities.
It's here that one objection might be raised against Tomasello's hypothesis (Clark raises a similar one in his post, and Jesse discusses it as well). The idea that the primary deficit from which autistics suffer is in the area of theory of mind (the ability to identify with conspecifics) is still somewhat controversial. A great deal of research has been conducted on the relationship between theory of mind and autism over the last 10-12 years, but most of it has relied on the false belief task (see the previous post on Tomasello for a description of this task). However, several researchers have argued that the false belief task does not actually test for theory of mind. Bloom and German, for example, have argued that the false belief task is a test of more than just theory of mind, and that there is more to theory of mind than is tested in the false belief task. Thus, individuals may have theory of mind abilities, but have deficits on other abilities that are tested in the false belief task, and thus be unable to perform the task. Conversely, they may not have fully developed theory of mind abilities, but pass the false belief task because it does not test for all of the aspects of theory of mind. Thus, it's difficult to conclude from autistic children's inability to perform the false belief task that those children do not have theory of mind abilities. Furthermore, autistic children are able to perform on other theory of mind tests, albeit at a later age than non-autistic children. It may be that autistic children have deficits in other abilities that underlie theory of mind as well as many of the other cognitive deficits that autistic children display. The leading theory is still that autism is related to theory of mind deficits, but exactly what this relationship is, and its effect on the many symptoms of autism is still unknown, and the topic of a great deal of current research. If it turns out that there is a common underlying cause of theory of mind deficits and other cognitive deficits in autism, Tomasello will have lost one of the strongest pieces of evidence for his hypothesis.
Returning to Chapter 1, immediately after the discussion of the ability to identify with conspecifics, Tomasello discusses one of the most important results of this ability: the ability to learn and use a uniquely human language (p. 8-11). It is here that Tomasello writes one of the most interesting and important passages in the entire book, so I will quote it at length:
As the child masters the linguistic symbols of her culture she thereby acquires the ability to adopt multiple perspectives simultaneously on one and the same perceptual situation. As perspectively based cognitive representations, then, linguistic symbols are based not on the recording of direct sensory or motor experiences, as are the cognitive representations of other species and human infants, but rather on the ways in which individuals choose to construe things out of a number of other ways they might have construed them, as embodied in the other available linguistic symbols that they might have chosen, but did not. Liguistic symbols thus free human cognition from the immediate perceptual situation not only by enabling reference to things outside this situation ("displacement" Hockett, 1960), but rather by enabling multiple simultaneous representations of each and every, indeed all possible, perceptual situations. (p. 9, emphasis mine)The point here is that language enhances the abilities to learn and transmit cultural knowledge, the very abilities that make the learning and use of language possible. Language opens up all sorts of cognitive avenues. Tomasello lists three of these (p. 10): metacognition, in which we think about our own thoughts and thought processes; representational rediscription, which allows us to rerepresent specific knowledge in a way that makes it possible to use it in a broader array of situations; and dialogical thinking, in which we are able to adopt multiple perspectives at once. In addition, language provides us with our most efficient method of cultural transmission. In short, then, through the creation of language, and by making it possible for children to learn language ontogenetically (i.e. developmentally), the abilities that underlie collaborative learning have in essence created an amplifier through which they can develop the full range of human culture and uniquely human cognitive abilities.
This account of the role of language fits nicely with the agent-based model of the creation of a lexicon that I described in a previous post. In simulations using that model, simple agents were able to develop a lexicon for describing all of the possible perceptual inputs in a simple environment. Furthermore, through the development of a consensus between the members of the community, the lexicon allowed the agents to better represent that environment. That consensus was developed entirely through social interactions (speaker-listeneinteractionsns). In fact, all you had to do to make it difficult for such a consensus to develop between two agents was to make it difficult for them to identify with each other. While the model is simple and idealistic, it serves as a nice existence proof of the viability and power of Tomasello's account of the role of language in amplifying cultural learning, and the power of cultural learning in developing a common language.
Now that I've summarized Tomasello's problem and hypothesis, I can briefly discuss one potential objection. Tomasello's hypothesis is motivated entirely by the existence of his problem. If it turns out that six million, or even 250,000 years, is enough time for multiple cognitive abilities to evolve through ordinary biological means, than Tomasello's hypothesis is no longer motivated. This is in fact one of the most common criticisms of the book that reviewers, particularly biologists, have mentioned. Fortunately, we have a few biologists in the group who can help us sort this issue out. In fact, one of those biologists, Bora Zivkovic (whom you may know as Coturnix) offered just this criticism in his post on Chapter 1. Bora argues that chimps may not be as similar to us as Tomasello thinks, which could mean that we must have evolved multiple cognitive abilities biologically in order to explain the uniquely human cognitive skills that we display today. Bora also notes that there are several well-known evolutionary mechanisms that could be used to explain the rapid evolution of multiple cognitive abilities. He lists the Baldwin effect, niche construction, sexual selection, and group selection (multilevel selection). Since I'm not a biologist, I won't attempt to explain these to you (read Bora's post and follow the links for good explanations), but I will note that the first two, the Baldwin effect (the link is to a PhD dissertation that provides a thorough review and critique of the use of the Baldwin effect) and niche construction, have been used in discussions of the evolution of language. If it is in fact the case that there has been enough time in our evolutionary history to develop multiple cognitive adaptations, then the rest of Tomasello's book is interesting, but the validity of the view it describes will be highly questionable.
But we haven't even begun to delve into the substance of Tomasello's arguments, so it's too early to bury his hypothesis entirely. In Chapter 2, he'll present his argument that the evolutionary time period was not sufficient for the development of multiple cognitive adaptations, and will discuss in more detail the process of "cultural inheritance." Things are just starting to get interesting.