Criticisms of the Mutual Knowledge issue

Clark’s theory has been attacked for a long time (see Smith, 1982 for an overview of the controversies). Linguists from the “pragmatic school” have issued two majors comments regarding the “Common Ground” theory and its various instances. Both are related to different aspects of the Mutual Knowledge issue, a recurrent problem in linguistics.

The first criticism concerns the representation of Common Ground. Historically, there have been two conflicting types of representation of the CG: CG-iterated and CG- shared6. Although they look similar, the two versions are not equivalent as we can see in Table 5. The CG-iterated representation refers to the series of checks an individual should do to ground the mutual understanding, whereas the CG-shared representation states that there is no need for these checks but that simply recognizing that a piece of knowledge is “shared” between the two conversants is sufficient.

Table 5. The two different representations of Common Ground for a proposition p in a community C of people (drawn from Clark, 1996).

CG-shared CG-iterated p includes the beautiful day, the beach, the

sea, A, B and a shell between A and B.

p includes A’s awareness of situation s p includes B’s awareness of situation s

The situation s is the shared basis for a common ground.

p is common ground for members of community C if

and only if:

1. members of C have information that p;

2. members of C have information that member of Chave information that p;

3. members of C have information that member of C have information that members of C have information that p;

4. And so on ad infinitum.

6 _{There is also the CG-reflexive but we will not enter into these details here since the reflexive version}

Paradoxically, most criticisms of Clark (and Lewis) have assumed that the only proper representation of the Common Ground was CG-iterated. They focused on sequences such as the one represented in the Table 5 and argued that such infinite regression is impossible from a cognitive load or time point of view (Green, 1987; Schiffer, 1972; Sperber and Wilson, 1986). As Clark also pointed out, CG-iterated is untenable as a representation of people’s mental state because it would require an enormous mental capacity: “CG-iterated obviously cannot represent people’s mental states because it requires an infinitely large mental capacity” (Clark, 1996, p. 95). By pointing out this fundamental problem, Clark contenders dismissed the very notion of Common Ground and left aside the CG-shared representation, which is less problematic.

This leads us to the second criticism of Clark’s theory. Even with the CG-shared version, some linguists still considered that the common ground notion and its components were flawed. Harsh comments have been made by the “inference” school of pragmatics, criticizing the Mutual Knowledge theories. To them, mutual knowledge or what Clark called common ground is not necessary for communication; they then developed a different framework based on looser notions. Sperber and Wilson (1986) are the most prominent authors who propelled this view, using concepts such as “cognitive environments” and “mutual manifestness” of facts in the participants’ environment. As they propose, “A fact is manifest to an individual at a given time if and only if he is capable at that time of representing it mentally and accepting its representation as true or probably true” (Sperber and Wilson, 1986, p. 39). Therefore, if two individuals A and B have the same perceptual and cognitive abilities, a fact will be considered manifest to A and B and the two of them would easily infer that, having the same abilities, this fact is “mutually manifest” (i.e. manifest to each of them). Sperber and Wilson state that the conversants share the same “cognitive environment”. An individual cognitive environment is the set of facts that are relevant to a person (i.e. that he or she can perceive and draw inferences upon it). When the same facts are manifest to two or more people, the participants share a “mutual cognitive environment”, which is the intersection of the individual representations. Additionally, sharing such a cognitive environment does not imply that they make the same assumptions since cognitive or perceptual abilities are not strictly identical among people. Sperber and Wilson then base their argumentation on how facts become relevant to individuals (what they call principle of relevance) and how people make them manifest to others (what they call ostensive behavior). The difference with Clark’s description of Common Ground, is that saying two people share a cognitive environment does not imply they make the same assumptions; merely that they are capable of doing so, as expressed by Sperber and Wilson.

Moreover, Sperber and Wilson’s criticisms also point out the fact that the idea of having “shared knowledge” is bound to a vision of language they define as passé. To them, this approach indeed emphasizes the “conduit” metaphor of communication, in which speaker’s interactions are thoughts encoded as verbal or non-verbal interactions which are decoded by an addressee. To these authors, the pragmatic level of communication is a new code layer added on top of the linguistic code. This is why, for Clark and others “within the framework of the code model, mutual knowledge is a necessity” (Sperber and Wilson, 1986: p18).

We will not go further into a description of Sperber and Wilson’s theory here. The point here was rather to show an alternative view.

However, these criticisms of Clark’s theory have focused on earlier versions (Clark and Marshall, 1981; Clark and Wilkes-Gibbs, 1986). In the final iteration of Clark’s theory, the introduction of the coordination devices as a part of the Common Ground seems to be a way to take into account the problems raised by Sperber and Wilson. The notion of coordination devices exchanged during a joint activity is actually not far from the mutual cognitive environment. As we saw, the Common Ground consists of the accumulation of coordination devices exchanged over time. We can then differentiate a local version of the CG that would only be made of the coordination devices available in the environment (manifest and perceptible elements, conventions discussed by participants or the messages exchanged). This local CG would correspond to the mutual cognitive environment. The problem is certainly that Clark contenders misunderstood the CG: to most of them, they reduce it as a stock of anterior knowledge, which is false. Like the mutual cognitive environment, the common ground, filled with situated facts (manifest or perceptually salient), is updated but in a more discrete way (devices after devices). To bridge the gap between both theories, we should name Clark’s coordination devices as “relevant element for inferences” using Sperber and Wilson’s terms because they offer a basis for drawing inferences. Choosing between different information sources to take a decision is an inference phenomenon, based on the relevance of the coordination devices.