Jerry Fodor on mental architecture

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Jerry Fodor is notable for his important and influential ideas on a hypothesized "structure" of the mind or, what has often been called mental architecture.

[edit] Fodor and Chomsky

Fodor maintains that Noam Chomsky’s criticism of language learning must be extended to cover all of the essential aspects of thought. In his The Language of Thought of 1975, Fodor presented his famous "impossibility thesis" with regard to the gradual acquisition of concepts. Suppose that you are a child in the first stage of such a process of acquisition and you must try to learn the concept X, a concept of the second stage. If something is a second-stage concept, then it cannot be coextensive with any first-stage concept, otherwise there would be no distinction in expressive power between the first and the second stages and no basis at all for such a hierarchy of learning stages. But if you are a child who cannot represent the extension of a second-stage concept in terms of the extension of some first-stage concept with which you are already familiar, then you cannot represent the extension of that second-stage concept X at all because the first-stage concepts are all that you have at your disposal. And if you cannot represent the extension of the concept, then you cannot learn the concept because the learning of a concept implies the projection and confirmation of the biconditionals which determine that the extension of the concept has been learned. The conclusion is that either higher-stage concepts are indeed representable in terms of (reducible to) lower-stage concepts (in which case there is no basis for the distinctions between stages and the hierarchy crumbles with no actual learning taking place) or there are concepts in the higher-level stages which cannot be represented in the lower-stages, in which case the child cannot learn them. Fodor’s conclusion is that an "extreme innatism" concerning concepts is necessary to explain learning. He will accept, for example, that the complex concept AIRPLANE may be composed out of simpler concepts such as FLYING and MACHINE. But he insists that the human mind is "richly endowed" with many fairly complex concepts such as Machine from birth. This view has been strongly contested.^[1]

In The Modularity of Mind, Fodor makes another crucial distinction between his approach to the mental and that of Chomsky. He attributes to Chomsky (and other so-called neo-Cartesians) the view that what are actually innate are (only) the intentional objects of propositional attitudes: the content expressed by the sentences of the language of thought. This, however, flies in the face of Chomsky’s own writings which have always tended to emphasize the existence of organs of the mind similar in structure and function to the modules talked about by Fodor. In any case, Fodor suggests, in this work, that his approach, unlike the others, attempts to explain what is required, other than content, to give rise to behaviour:

"If you say '19' when I say '7 plus 12, please', your reply could undoubtedly be explained in part in reference to your knowledge of numbers. But this is not enough, given that, after all, knowledge does not translate into behaviour in virtue of only the content of propositions. It seems evident that mechanisms are needed which put into action that which is known, mechanisms which have the function of making the organization of behaviour conform to the propositional structures which are known."^[2]

The connection between functional architecture and content is therefore required in order to explain one of the most relevant questions of the program of naturalization of the mental and the explanation of behaviour in causal terms.

[edit] Why modularity matters

The Müller-Lyer optical illusion with arrows. All three arrows at the top, though they appear to be different, have the exact same lengths. The bottom part of the diagram demonstrates their equality

Fodor thinks that a (moderately) modular view of the structure of the mind is necessary to explain the strong degree of autonomy from the central system that certain properties of perception demonstrate. He cites the case of experiments which demonstrate the specificity of domain of the mechanisms which act during the analysis of phonetic information. These experiments apparently demonstrate that the mechanisms of phonetic analysis are exclusively sensible to acoustic sequences of spoken language. But, according to Fodor, what really distinguishes modules from central processes is what he calls informational encapsulation. This is roughly the thesis that modules are much less open and permeable to background knowledge and beliefs on the part of the individual. Fodor uses the persistence of perceptual illusions to illustrate his thesis. Illusions, such as Müller-Lyer tend to persist long after a subject has been exposed to them and has learned that the two lines are, in fact, equal in length. The knowledge that the two lines are equal is cognitively available and constitutes part of his background knowledge which he can access consciously at any time. Nevertheless, when looking at the rods, one still effectively sees them as uneven and the illusion persists. This suggests to Fodor that basic perceptual modules are partly closed off from the cognitive background knowledge of the subject: modules are informationally encapsulated. The study of perception is of fundamental importance for illustrating the connection between functional architecture and the theory of mental content. The fact that perception exhibits characteristics of autonomy and independence from central processes (and that it is relatively impenetrable to background knowledge) can be posted at the base of a theoretical conception able to mediate between internalist conceptions (hence preserving representational realism) and externalist conceptions (hence allowing for a causal-informational conception) of mental content.

Fodor’s proposal is characterized by the attempt to converge the causal conception with the inferential thesis of perception. His goal is to break the bond between the inferential thesis and the thesis of the dependence of perception on the system of beliefs/desires of individuals. Basing itself on the importance of background knowledge in perceptual processes, the inferential conception has been utilized in favour of the epistemic hypothesis of perception. This hypothesis fits perfectly with the inferential thesis because it explains the derivation of the hypotheses that the perceptual system projects on the proximal stimulus. The result is a notion of the cognitive permeability of perception: seeing is an interpretive act which depends on the background knowledge of the subject. According to Fodor, however, it is possible to adhere to the inferential thesis without having to subscribe to the idea of cognitive permeability. From the fact that perceptual processes are inferential it does not follow that they must have access to the background knowledge of subjects. But, in order for all of this to work, perceptual systems must be "specialized" and "encapsulated." Our best theory of perception, therefore, seems to require a modular organization of the mind.

[edit] Gibson and the inferential thesis

So why is the inferential thesis necessary for Fodor and how does he justify it? In an article called How Direct is Visual Perception: Some Reflections on Gibson’s "Ecological Approach", Fodor and Zenon Pylyshyn criticize the conception of perception proposed by James Jerome Gibson in 1979.^[3] The so-called ecological approach is in sharp contrast with the Establishment Theory maintained by cognitivists. The cognitivist thesis considers perception precisely to be a form of inference (seeing IS making hypotheses about the world). Three factors are necessary in order to sustain this thesis: memory, representation and a mechanism of elaboration able to transform—according to certain rules—some representations (premises) into other representations (conclusions). The reference to representations renders perception a mediated process which is highly indirect. Against this, Gibson proposes an hypothesis of perception capable, in his view, of doing without these three factors (and which is therefore qualified as direct . To perceive, in his hypothesis, is to directly gather, without any representational intermediation, the invariant properties of the environment. But what are these properties?

Fodor points out that in order to avoid a "trivialization problem" (that is, the possibility that anything can be counted as an invariant property), Gibson must offer some criterion capable of tying together the gathering of information and the environmental invariants:

Suppose that under certain circumstances people can correctly perceive that certain things in their environment are of the type P. Since it is not possible to correctly perceive something of the type P unless it really is P, it is always trivially true that the things that can be perceived as P share an invariant property: their being P. Now, since, according to Gibson, that which people do when they perceive is to directly gather an appropriate invariant, for every perceptual result the following pseudo-explanation will always be valid: to perceive that something is P is to gather the invariant property P that the things of this type have.^[4]

An illuminating example of the argumentative circularity which underlies the attempt to tie "direct grasping" to the invariant properties of objects can be seen in one of the key points of Gibson’s theory, according to Fodor. This is the thesis according to which the privileged invariants of objects are a sort of "affordances", or dispositional properties (being eaten, being grasped, being launched, etc.) which the objects offer to the organisms with which they come into ecological contact. Against this hypothesis, Fodor shows that such "affordances" presuppose direct perception and cannot be used to explain it.

The impossibility of direct perception of distal objects makes it necessary, according to Fodor, to adopt an inferential theory (necessarily mediated and indirect) of perception. The computational mechanism at the base of inferential processes is represented by the transducers. These are the mechanisms capable of providing a representation (in atomic structures of the LOT) of the dispositions of distal objects on the basis of the properties of the proximal stimulus. Given the huge gap which exists between proximal stimulus and distal object, it isn’t possible to propose a direct conception of perception (every perception is mediated by the representations which bridge the gap between distal object and proximal stimulus). Fodor’s conception remains within the context of the representational theory of the mind. Gibson, in his view, fails to clear the field of this theory because it is basically ineliminable, given that all of the semantic questions of perception seem to necessarily refer to it.

Fodor also addresses the problem of intentionality, one of the central aspects of the question of perceptual content which seems to be insoluble from the point of view of Gibson’s theory. The key point of Fodor’s criticism of the thesis of direct perception is that, given the same identical stimulus, we are able to form many different representations of the same object (seeing it as the morning star or as the evening star) and this in turn will tend to give rise to different behaviours. Even though there is a sense in which we see merely extensionally, therefore, seeing is substantially intentional. And the intentional aspects are, in fact, those which have causal relevance in any explanation of human behaviour. Inference, representation and intentionality seem to be, Fodor believes, intimately related. Gibson’s problems arise from not having comprehended this fact.

[edit] The limits of interpretation

Jastrow's duck-rabbit illusion

If the question of intentionality is the critical notion in Fodor’s criticism of Gibson, in Observation Reconsidered the same notion plays a specular role: the limitation of the interpretationalist conception of perception.^[5] The question regards the fixation of beliefs. Traditionally, the theories in this area tend to concentrate on two hypotheses: those which privilege the perceptual aspects and consider the fixation of beliefs to be dependent on perception and, therefore, on the relation with the external world; and those that, privileging instead the inferential relation between old and new beliefs, consider the fixation of beliefs to be substantially a process internal to the organism. While Fodor admits that the internal relation between beliefs has an enormous value, he maintains that this aspect has been overemphasized in recent philosophy of science and philosophy of mind. Fodor’s intent is to try to re-establish a just equilibrium between interpretation and observation.

The interpretationalist theories have a strong and consolidated tradition behind them. Ludwig Wittgenstein in his Philosophical Investigations (1953) distinguished between seeing that and seeing as using the well known experiment of ambiguous figures (Jastrow's duck-rabbit).^[6] Ambiguous figures force us to confront the fact that perception cannot be determined exclusively by sensory stimuli: given the same stimuli, it is possible to give two (or more) different interpretations of the same retinal configuration. Processes of interpretation are necessary in order to give sense to mere sensory stimulation. One author who has strongly insisted on this point is Jerome Bruner (1957), one of the founders of the New Look in the psychology of vision.^[7] The most radical thesis in this regard, however, is that which, above all in linguistics and anthropology, has taken on the name of the Sapir-Whorf hypothesis . This hypothesis asserts that every perceptual act is determined and constituted by the entire web of beliefs of the individual (in fact, by his whole culture). This is a strongly holistic position which Fodor vehemently opposes and criticises. The tight relation between the interpretationalist hypothesis and holistic conceptions of belief is at the base of the idea of the dependence of perception on theory. This idea has profound repercussions also in epistemology. Thomas Kuhn (1962), Norwood Russell Hanson (1958) and Nelson Goodman (1968), for example, maintain that the perception of the world depends on how the percipient conceives the world: two individuals (two scientists) who witness the same phenomenon and are steeped in two radically different theories will see two radically different things. It is our interpretation of the world, in this view, which determines that which we see.

Fodor attempts to establish that this theoretical paradigm is fallacious and misleading by demonstrating the impenetrability of perception to the background knowledge of subjects. The strongest case can be based on the evidence from experimental cognitive psychology itself: the persistence of perceptual illusions. Just knowing that the two horizontal lines in the Muller-Lyer illusion are equal does not prevent one from continuing to see them as one being longer than the other. It is this impenetrability of the information elaborated by the mental modules (informationally encapsulated) which limits the extent of interpretationalism.

The criticism of the interpretationalist hypothesis accounts for the common sense intuition (at the base of naïve physics) of the independence of reality from the conceptual categories of the epistemic subject. If the processes of elaboration of the mental modules are independent of the background theories, in fact, then it is possible to maintain the realist view that two scientists who embrace two radically diverse theories see the world exactly in the same manner even if they interpret it differently. The point is that is necessary to distinguish between observations and the perceptual fixation of beliefs. While it is beyond doubt that the second process involves the holistic relation between beliefs, the first is largely independent of the background beliefs of individuals.

[edit] Clearing the way for realism

Maintaining that scientists see the same world but interpret it differently does not explain, according to some critics, scientific dispute. According to Fodor, however, the true point in discussion is not the question of understanding what distinguishes various theories from each other, but what it is that permits scientific consensus. His answer to this problem is that scientific consensus is indissolubly linked to the thesis of the independence of observation from theories. Despite the interpretative differences, that which scientists share is that which depends on their belonging to a species endowed with certain common cognitive-perceptual structures. The question is also important because it has repercussions on the plane of semantics and mental content.

[edit] References

1. ^ Fodor, Jerry A. (1988). The Modularity of Mind: An Essay on Faculty Psychology. The MIT Press. 
2. ^ Fodor, Jerry A. (1975). The Language of Thought. Thomas Cromwell. 
3. ^ Gibson, J.J. (1979). The Ecological Approach to Visual Perception. Houghton Mifflin. 
4. ^ Fodor, Jerry A. and Pylyshyn, Zenon. "How Direct Is Visual Perception? Some Reflections on Gibson's Ecological Approach". Cognition (9): 139–196.  on-line preprint
5. ^ Fodor, Jerry A. (1990). A Theory of Content and Other Essays. The MIT Press. 
6. ^ Wittgenstein, Ludwig (1953). Philosophical Investigations. Basil Blackwell. 
7. ^ Bruner, J. (1957). "On Perceptual Readiness". Psychological Review (65): 14–21.