Mental Content

Causal Theories of

representation# nomic covariation #disjunction problem# functional role#holism

Wallis, Charles

Charles Wallis

California State University, Long Beach, California, USA

What are Causal Theories of Mental Content?

Causal theories of mental content hold that mental states represent the world in virtue of the sorts of causal relationships those states have within the mind and with the world. Though many theories of mental content are causal theories, not all theories of mental representation are causal in nature. For example, John Locke supposes that ideas of primary qualities, like shapes and colors, represented those qualities in an object because they were similar (share the same properties.). Contemporary causal theories of mental content have predecessors dating back to Book III of John Locke's Essay Concerning Human Understanding, possibly Aristotle's De Anima , or even to Plato's Theatetus . Locke's notion of secondary qualities (a quality or power of the object to cause particular ideas in us which bear no similarity to the object, e.x. color) looks very much like a contemporary causal theory based upon reliable causally mediated covariation (Cummins 1989). Aristotle 's discussion in Book II of De Anima suggests that, for example, color in the object though different from sensations of color is nevertheless reliably caused by light hitting the object. Plato's analogy of perception as the matching of sensations caused by the world to impressions (knowledge) upon a ball of wax also suggests that Plato entertained the notion that causal connections allowed our minds to represent. Contemporary causal theories of mental representation have developed in the theoretical context of explanation in cognitive science. Though such theories can be understood independently, it can be helpful to view causal theories in the context of computation explanations in cognitive science.

The "Computational Theory of Cognition" ( CTC ) and the "Representational Theory of Intentionality" ( RTI ), form the foundation of cognitive science. CTC characterizes cognition as the computation of complex functions on representational states. Computation consists in performing operations defined over representational states. Operations can be rule-based manipulations of syntactic strings as in traditional artificial intelligence, or the weighted passing of activation as in connectionist models. RTI asserts that mental states are about the world (have content) in virtue of a representation relation holding between the world and those states. CTC / RTI portrays cognizers as receiving input through sensory organs and/or memory and generating outputs in the form of memories, inputs to other processes, and/or motor response commands.

Figure 1

Debate over the concept of computation relevant to the CTC centers around, on the one hand, Turing -compatible computation and its development in computer science and mathematics, and on the other hand dynamically described state transitions (ex. Connectionism ). A similar dichotomy of theories occurs in the literature on representation. Neither theory regarding the representation relation presupposed by the RTI has gained general acceptance. However, there are several agreed-upon constraints for a theory of representation. First, the representation relation must be consistent with the physicalistic nature of cognitive science. Second, the relation must be present and explanatory in accepted explanations within cognitive science.

Varieties of Causal Theories of Mental Content

One theory, Nomic Covariation , postulates a causal relationship between the mental state and the object or property that state represents. The other theory, Functional Role Semantics, hypothesizes that a state has content in virtue of the state's occupying a particular position in a complex web of causal relationships characterizing the cognizer 's functioning. Candidate content-fixing causal relationships may include causal relationships within the cognizer and/or without. Both functional role and covariation theories satisfy the (above) first, physicalistic constraint, since they suppose a cognizer 's states represent the distal environment solely as a result of the specific sorts of causal connections had by those states. The theories diverge in terms of the specific causal relationships each emphasizes.

Nomic Covariation

Nomic covariation theories define content in terms of a causal connection between a given object or property in the world and the state that represents that object within the cognizer . Contemporary Covariance theorists claim to draw their inspiration from information theory as well as work within psychophysics.

...there are circumstances such that red instantiations control 'red' tokenings whenever those circumstances obtain; and it's plausible that 'red' expresses the property red in virtue of the fact that red instantiations cause 'red' tokenings in those circumstances; and the circumstances are nonsemantically , nonteleologically , and nonintentionally specifiable.

In fact, they're psychophysically specifiable. ( Fodor 1988, p.112)

Covariation theories seem to satisfy the second constraint upon theories of representation, i.e., that the relation must be present and explanatory in accepted explanations within cognitive science. For example, Hubel and Wiesel (1977) investigated the representational content of cells in the striate (visual) cortex by monitoring the activity of those cells looking for law-like relationships between the activity of these cells and the presence of properties in the visual field. Covariationists hypothesize that a system's states represent those objects and/or properties of the distal world with which they covary . More precisely, nomic covariation assigns contents to states via the following definition (Cummins 1989, Fodor 1988):

State, Sb, represents B iff the system tokens Sb when, only when, and because of B.

Advantages of Nomic Covariation

Covariation gains intuitive plausibility in that a cognizer represents an object/property by being causally "in tune" with that object/property. Covariationists such as Jerry Fodor advocate covariation because it assigns content to individual states, Sb independent of how the cognizer operates upon those states (inferences it can make) and/or the content of other states with which Sb might interact. Fodor refers to this assignment of content as " punctate content, or "atomic content." Fodor claims that punctate content allows for content identity across individuals having quite different theories regarding the object/property. Similarly, punctate content provides the only theory whereby people can refer to objects even when they have great numbers of false beliefs about them. For instance, Fodor claims (1992) that Aristotle thought about and talked about stars even though he falsely believed them to be relatively close and rotating around the Earth on glassy spheres. The systematicity and compositionality argument for covariation theories supposes that covariation theories are in a better position to explain perceived truths about the combinatorial properties of language an concepts. Compositionality is the theory that the meaning of a complex expression in a language results from the meanings of its constitutive elements. Compositionality plays an central role in many linguistic theories, since its supposition for both language and thought provides a fairly straightforward explanation of the human ability to grasp an enormous number of different thoughts of varying complexity and their corresponding linguistic expressions. Covariation boasts a final perceived advantage in that it provides a clear-cut mechanism through which a system can come to know about an object/property in the world in virtue of its representational capacities. Cognizers that represent an object/property do so insofar as they can reliably detect its presence in the environment.

Problems for Nomic Covariation

Cognitive scientists, particularly philosophers, recognize that covariation theories face a number of standard objections. Firstly, lawful covariation between a state and an object/property cannot straightforwardly explain representation of non-existent objects/properties. Another objection challenges the ability of covariation to explain the representational capacities of states with regard to objects/properties beyond low-level perceptual properties ( e.x. edges), especially very abstract, high-level objects and properties like God or photon. Advocates of covariation suppose that covariation determines content for states representing objects/properties ranging from low- level properties (edge or blob), to ordinary objects and properties (dog or chair). Properties/objects associated with thoughts of a higher level of abstraction, like photon, get represented by states in virtue of their being defined in terms of the representational properties of lower level states. ( Fodor 1988)

Robert Cummins (1989) objects that covariation of states with objects/properties requires either implicitly or explicitly represented heuristic information in the system. Thus, covariation will not explain the representational properties of any states but the primitive representational states. All higher level concepts from table to totalitarian must get meaning through definition. At first glance, it seems plausible to suppose that states that represent high-level theoretical properties like photon get their meaning through definition in terms of lower level properties. After all, such properties and objects often have theoretical definitions. However, the failure of such semantic reductions has shaped the history of Western Philosophy and Mathematics (Quine 1953). Worse still the more ordinary the concept, the less readily one accepts that one knows its meaning because one has an explicit definition. For example, covariation 's critics ask why, if the state one uses to represent panda gets its meaning from being defined in terms of lower level properties, why does one have difficulty in articulating that definition in any but the most superficial sense? Psychological research seems to weigh against such semantic reductionism as well in that it indicates that object recognition and categorization are strongly influenced by perceptual features, the exact make-up of which is relatively variable.

For Cummins, mental states covary with cats because one already has knowledge about cats (ex. They are domesticated felines) that we explicitly represent. Further, if covariation is not the simple, unmediated causal relationship between the property or object and the state, but rather the result of often complex causal interactions within the system, covariation starts to look like another instance of its competitor, functional role semantics.

The third, and most widely discussed problem for covariation , is called the "Disjunction Problem". According to covariationists , a state represents an object or property if the system tokens (enters into) that state when confronted with the object or property and ONLY IF confronted with that property. Suppose that a cognizer has a state, Sc, that appears to represent cathood . In fact, the cognizer tokens this state in all of it's cat interactions. However, one night the cognizer sees a possum in the half light and tokens Sc. The only if clause of the Nomic Covariation definition prima facie dictates that Sc never really represented cat. Rather, the cognizer has always represented a property that one might describe using the disjunction, "cat or possum".

The disjunction problem poses difficulties for covariation theories in two ways: First, the theory seems to dictate counter-intuitive representational contents for states. If one has beliefs about cats ( e.x. cats are domesticated felines having a number of distinct breeds) then covariation would seem to dictate that you in fact have a belief that things having the property of being either a cat or a weasel have those qualities. Second, and most widely discussed, the disjunction problem seems to show that covariation cannot account for misrepresentation, since any seeming case of misrepresentation by a cognizer becomes correct representation of a disjunctive property under Nomic Covariation . In other words, one never mistakenly believes that one sees one's mother at the corner, one always correctly believes that "mother/other" is at the corner.

Covariationists suggest a number of solutions to the disjunction problem. All of these solutions rely upon some form of idealization: A given solution will separate cases of the tokening (occurrence) of a state into two groups, one in which content is already fixed and representational error can occur, and the second (ideal circumstance) class in which content is fixed by perfect covariation . There are several important versions of this solution:

Ideal Conditions

Advocates of the ideal conditions solution to the disjunction problem suggest one represents "mother" and not "mother/other" despite occasionally mistaking others for mothers because under ideal perceptual conditions (i.e., in good light, at close distance, etc.) one can always distinguish mothers from others. Difficulties arise for the ideal conditions solution when one tries to specify in a precise, and non-question-begging way what would count as ideal conditions for a given case. For instance, in the movie "The Crying Game" an Irish man becomes romantically involved with a woman. However, much to the surprise of the Irish man (and the audience) this woman is actually a man. The reaction of the Irish man clearly shows he misrepresented the gender of his romantic partner. However, he did see him in good light, at close distance, etc.. The natural suggestion would be that there are conditions under which such a difference would not escape notice. However, in specifying such conditions as ideal conditions for this case, one must be guided in a circular manner by one's knowledge of the property that the state actually represents.

Critics (Wallis 1994, 1994a ) also argue that appealing to idealization to defeat the disjunction problem is strongly and negatively disanalogous with successful uses of idealization is science.

Learning Periods

Fred Dretske (1981) suggests that a learning period fixes. In this period, cognizers develop perfect causal connections between states and objects/properties with the help of an instructor who provides examples and corrections. Once the learning period ends, the cognizer 's state has a fixed content and tokenings of the state in cases where the object/property is absent count as misrepresentations.

Fodor (1988) and others criticize this approach on two grounds. First, there seems to be no principled distinction between learning and non-learning periods, hence there seems to be no grounds for calling some tokenings of the state content imbuing and others representing or misrepresenting. Second, even if one could specify a learning period, there seems to be no principled distinction between the univocal and disjunctive causal connections. Critics ask why one ought suppose that causal connections created in the learning period hold between, for example, cats and Sc and not between cat/possum and Sc?

Teleological Accounts:

Advocates of a teleological solution to the disjunction problem, such as Ruth Millikan (1983, 1986), suggest that evolutionary history determines content. For example, a frog captures and eats any ambient moving dot in its visual field. As a result, hungry frogs eat ball-bearings rolled in front of them. Advocates of the teleological account claim that frogs misrepresent ball-
bearings as flies because the function of a frog's visual cells is determined by the uses of those cells responsible for a frog's ability to propagate it's genome, i.e., uses involving fly capturing.

Fodor (1988) objects to teleological accounts in that evolutionary selection lacks sufficient precision to account for typical univocal content claims. If frogs represent ambient dots as "fly or ball-bearing" in a fly-rich, ball-bearing-poor environment, then that disjunctive content would account for the frog's ability to propagate it's genome. Hence, evolutionary history will not favor "fly" over "fly or ball-bearing" as the content of frog visual cells.

Other objections to teleological accounts appear in the literature. First, most artifacts ( e.x. , computers, SUVs , etc.) were not present during the majority of human evolutionary history. Advocates of teleological solutions to the disjunction problem must, therefore, explain a huge percentage of the representational capacities of humans, including the representations of many ordinary objects (chairs or beer), by definition. Second, (Cummins 1989, Davidson 1987) since teleological accounts appeal to the evolutionary history of a cognizer to explain representational abilities, any seeming representational abilities without such a history would lack representational content on the teleological account. For example, if a molecule for molecule duplicate of Millikan where to spontaneously appear, it would seem to have all of her cognitive/representational abilities. Yet, on Millikan 's account, her exact double would have states lacking any representational content. Finally, Cummins argues that one cannot appeal to the adaptational significance of a state to explain its representational content, since in order for the state to have adaptational significance it must play a part in the cognitive capacities the system, and hence already have representational content.

Asymmetric Dependence

Fodor 's (1990) asymmetric dependence theory suggests another twist on the general idealization strategy. In addition to a nomic connection between a state, Sc, and an object/property, cathood , asymmetric dependence defines representation in terms of two counterfactual scenarios: If, say, possums cause Scs , then (1) breaking the possum to Sc connection does not break the cat to Sc and (2) breaking the cat to Sc connection does break the possum to Sc connection. As above, potentially troublesome cases get ruled out because there is a (counterfactual) set of conditions in which subjects can distinguish cats from possums. Critics (Cummins, 1989 Wallis 1995) argue that asymmetric dependence theories fare no better than other versions of covariation . One difficulty is that the brain recognizes higher level concepts through the detection of features. As a consequence, it appears that there is no asymmetric dependence between cases, or worse, it goes the wrong way from fake to representation. For instance, if I find my car by looking for features x,y,z , then I can break the car to Scar connection by altering the appearance of my car. But that will not break the look-alike to Scar connection (violating 2). If, on the other hand, I break the look-alike to Scar connection, then it seems I do break the car to Scar connection (violating 1). Similar stories can be told in terms of the normal, albeit somewhat noisy, functioning of cells in the visual system.

Functional Role Semantics

Whereas nomic covariationists focus upon a single causal connection in fixing content, advocates of functional role semantics (Block 1986 and 1987, Field 1977 and 1978, Harman 1987), suggest that the overall network of causal relations into which a state can enter fixes its content. Often causal roles are specified functionally/computationally. Versions of functional role semantics include "conceptual role semantics," "procedural semantics," or "inferential role semantics". There are two versions of this approach designated "wide" or "long-armed" and "narrow" or "short-armed". Narrow functional role theorists limit the causal relations that determine content to those occurring between mental states. Wide theorists allow connections to the distal environment and even social contexts to delimit the content of a state.

Functional role theories have several attractive features. First, they do not need bifurcated accounts of representational content since all states get their content in the same manner, via their functional role. Hence, functional role theorists avoid explaining the representation of high-level properties by defining them in terms of low-level properties. Second, functional role theorists can easily accommodate the observation that changes in beliefs can result in changes in representational content, since changing beliefs will often change the functional roles of states. Finally, functional role theorists can capture the intuition that in trying to understand the representational content of another cognizer 's state, one is constrained by the heuristic that the overall set of content ascriptions must "make sense," i.e., be consistent with the supposition that overall, the cognizer 's interactions with the world are intelligent or rational.

Objection 1: Semantic Holism

Theorists typically raise three distinct but related objections to all versions of functional role semantics. First, identifying particular states in disparate individuals as states having the same representational content prima facie requires that the states have identical functional roles. Fodor (1992, 1987) calls this view "Holism," about content (also "Semantic Holism"). Suppose for example, that it appears that both Bill and Bob believe that "Wallis' article is enlightening." They both point to the same article, proclaim it enlightening, assign it in their class, etc.. However, the causal roles of their respective states differ in a single respect; Bill believes "Wallis is a pompous know-it-all," while Bob believes "Wallis is a precocious windbag." Prima facie, functional role semantics dictates that Bill's belief that "Wallis' article is enlightening," has a different content than Bob's. Similarly, people with disparate cognitive or perceptual abilities seem to have disparate representational contents. Thus, the theory appears to imply that the average human has a different concept of traffic light than color blind humans.

Functional role semanticists generally adopt one of two responses to the above objection. One response prunes the number and/or kind of causal or computational connections necessary for belief/content identity, thereby allowing for belief/content identity across individuals with somewhat different causal/computational roles. Differences in beliefs that are peripheral to"Wallis' article is enlightening" would not necessarily constitute the basis for content non- identity.

While the just-rehearsed response has intuitive appeal, critics ( Fodor 1988) emphasize the potential difficulties in distinguishing core (central) beliefs or other causal links from peripheral ones in a manner that is not hopelessly unsystematic and ad hoc. For instance, what causal connections (beliefs, desires, dispositions to take action, etc..) constitute the core of one's belief that the colorless, tasteless, odorless liquid is water. Need one know, to take a case, of the existence of deuterium oxide (heavy water), make appropriate inferences with regard to D2O , discriminate between D2O and H2O, etc.. In the case of beliefs and inferences, one common suggestion for distinguishing core from peripheral beliefs and inferences includes only analytic beliefs and corresponding inferences in the set of core beliefs and inferences. Analytic truths are conceptual truths, those things that are true solely in virtue of the nature of the concept. Such a suggestion requires a real distinction between analytic beliefs and non-analytic (synthetic) beliefs. Many philosophers believe that Quine (1953/1970) has effectively undermined the robustness of such a distinction. Similarly, Stich (1983) argues that judgements of belief/content identity are not as intuitively precise as advocates of the analytic distinction predict.

The second response to the prima facie difficulty of intuitively identical content across differing functional roles claims that while such beliefs are in fact non-content-identical, they are strongly content-similar. The key concept is that belief identity is not a binary notion, but ranges from completely non-identical to completely identical (Cummins 1989). The strength (or weakness) of this response lies in its ability to accommodate the intuition that Bill's and Bob's beliefs have the same content while simultaneously acknowledging the theoretical constraint that differences in functional roles dictate differences in content.

Critics argue that a graded notion of content identity, in addition to being counterintuitive, undermines the ability to formulate psychological generalizations and subsume particular cases under those generalizations. Cognitive science, they claim, would be reduced to the unworkable notion that Bill's and Bob's beliefs are, say, 97% content similar to the belief that Wallis' article is enlightening and hence can be, say, 97% subsumed under generalizations regarding the belief that Wallis' article is enlightening. Furthermore, Fodor (1992, 2001) claims colloquial notions of belief similarity like, "His notion of mental representation is similar to mine," as well as their theoretical counterparts presuppose a notion of belief identity that he claims cannot be provided by holistic theories in any cases where beliefs diverge.

Objection 2: Content Fixing, Error, and Univocal Contents

A closely related objection to holism is the argument that functional role theories have no non-arbitrary way either of fixing content, distinguishing representational error from veridical representation, and/or they result in non- univocal content ascriptions or multiple content ascriptions applying simultaneously to a given state. For example, suppose there are two worlds: one, call it Earth1 in which there is no water, but in which D2O (or some chemically different, but phenomenally similar substance) is plentiful; the other, call it Earth2 , where H2O is plentiful, but there is no D2O . Bob grows up on Earth1 forming beliefs, etc. about "water" as a result of interacting with D2O . Bill matures on Earth2 developing the exact same set of beliefs, etc. about "water" as Bob, but based upon interacting with H2O. Narrow functional role theorists (using only causal connections "internal" to the cognizer ) holds that the two men must have identical belief content when thinking about "water". They either form beliefs, make inferences, etc., using states that represent what we would describe using the disjunction, "H2O or D2O ", or their states represent both H2O and also D2O (as distinct entities) simultaneously. Most philosophers consider the latter even less intuitively plausible than the former.

Long arm or two factor theories can distinguish Bill's and Bob's beliefs since they include causal connections to environmental objects and/or properties. However, suppose that Bob also has the beliefs that "water is H2O," that "I live on Earth2 ," and " Earth2 has only H2O on it's surface." Is Bob representing "water" as D2O , but forming a false belief about the chemical structure of D2O ? Or, is he representing "water" as H2O and forming false beliefs about the D2O he finds in his environment. Critics assert that Functional Role Semantics lacks the resources to disambiguate such scenarios.

Finally, Fodor and LePore (1992) McLaughlin (19891), and Fodor and Plysyhyn (1988) object that functional role semantics seems to violate truths about the structure of language and thought like compositionality and systemativity . Compositionality is the theory that the meaning of a complex expression in a language results from the meanings of its constitutive elements. Compositionality plays an central role in many linguistic theories, since its supposition for both language and thought provides a fairly straightforward explanation of the human ability to grasp an enormous number of different thoughts of varying complexity and their corresponding linguistic expressions. For instance, because we understand the individual elements like "cup" and "coffee", we understand the complex expressions "cup of coffee," "coffee gives me the shakes," etc.. One explains our understanding by noting that the meaning of these complex sentences is built-up from the meaning of their constitutive elements.

Critics claim that the functional role of a complex, non-idiomatic representation is not always a function of the functional roles of its parts. As a result, functional role theories can represent "cup of coffee" without having the concepts and associated inferences of "cup" or "coffee". This alleged aspect of functional representation schemes would result in the possibility that one could represent and think about "cup of coffee," but could not represent or think about "iced coffee," "hot coffee," etc..

Causal Theories of Mental Content and Cognitive Science

Cognitive Science proceeds in the absence of a resolution of the debate over theories of representation. However, the adoption of either covariance theories or functional role semantics shapes the research of individual cognitive scientists. Many important debates in cognitive science have resulted from allegiance to one or the other causal theory. For example, one aspect of the connectionist vs Turing -compatible approaches is that advocates of connectionist frameworks tend to adopt functional role semantics, while advocates of Turing -compatible frameworks tend to adopt covariation . Similarly, the debate over the nature of mental imagery was drawn along covariance vs functional role lines. It is widely supposed that the adoption of one or the other theory of mental content by the majority of cognitive scientists will have a profound impact on the field.

Glossary

Compositionality #The theory that the meaning of a complex expression in a language results from the meanings of its constitutive elements.

Systemativity #The theory that there are intrinsic dependencies between certain thoughts such that lacking the ability to have one thought would result in lacking the ability to have the other. For example, Fodor claims that thoughts like "Bill is taller than Mary" are such that to have them one must also be capable of having the thought "Mary is taller than Bill".

Psychophysics# The scientific study of the relationships between physical stimuli and perceptual phenomena.

Nomic Covariation #Law-like covariation between objects or events.

Semantics#The study of the relationship between representations and what they represent, including theories regarding denotation, extension, naming, and truth.

Semantic Holism#The doctrine that beliefs get their content in virtue of their direct and indirect functional relationships to all other beliefs.

References

Block, N. (1986) "Advertisement for a Semantics for Psychology," Midwest Studies in Philosophy 9:283-328.

Block, N. (1987) "Functional Role and Truth Conditions," Proceedings of the Aristotelian Society suppl. 61: 157-181.

Cummins, R (1989) Meaning and Mental Representation. Cambridge: MIT Press.

Dretske , F. (1981) Knowledge and the Flow of Information. Cambridge: MIT Press.

Field, H. (1977) "Logic, Meaning, and Conceptual Role," Journal of Philosophy 74: 379-409.

Fodor , J. (1988) Psychosmeantics . Cambridge: MIT Press.

Fodor , J. and Pylyshyn , Z. ( 1988b ). " Connectionism and Cognitive Architecture: A Critical

Analysis," in Cognition. 28: 3-71.

Fodor , J. (1990) A Theory of Content and Other Essays. Cambridge: MIT Press.

Fodor , J. and McLaughlin, B. (1991). " Connectionism and the Problem of Systematicity :

Why Smolensky 's Solution Doesn't Work," Connectionism and the Philosophy of Mind. Boston: Kluwer Academic Publishers.

Fodor , J. and LePore , E. (1992) Holism: A Shoppers' Guide. Oxford: Blackwell.

Fodor , J. (2001) The Mind Doesn't Work That Way. Cambridge: MIT Press.

Harman, G. (1987) "(Non- solipsistic ) Conceptual Role Semantics". New Directions in Semantics, ed. Lepore , E. London: Academic Press.

Hubel, D. and Wiesel, T. (1977) " Ferrier Lecture: Functional Architecture of Macaque Monkey Visual Cortex." Proc. R. Soc. Lond . 198:1-59.

Millikan , R. (1983) Language, Thought and other Biological Categories. Cambridge: MIT Press.

Millikan , R. (1986) "Thought Without Laws: Cognitive Science Without Content." Philosophical Review 95:47-80.

Quine, W. (1953) From a Logical Point of View. Cambridge: Harvard University Press.

Quine, W. (1960) Word and Object. Cambridge: MIT Press.

Stich , S. (1983) From Folk Psychology to Cognitive Science. Cambridge: MIT Press

Wallis, C. (1994) "Ceteris Paribus Laws and Psychological Explanation," Philosophy of Science Association 1994. 1: 388-397.

Wallis, C. ( 1994a ) "Representation and the Imperfect Ideal," Philosophy of Science. 61: 407-428.

Figure 1 Elements of computational explanations of cognitive capacities in Cognitive Science