I.       Introduction

Most human mental representations arise as a result of development. These developmental processes depend on rich interactions with the thinker’s environment.  This paper argues that the details of those interactions are often part of what makes it the case that a particular representation has the content it does. Section 2 motivates the idea with examples from the development of relatively low-level psychological capacities. Section 3 considers human learning, using examples to draw out the reason why content is partly fixed by circumstances of development. The final section relates this claim to Laurence & Margolis’ important paper arguing for the importance of development (Laurence & Margolis 2002).

II.      Examples: low-level development

This subsection gives examples of four learning systems in animals where, intuitively, the end state representation refers to the thing encountered during the development of that end state. These mechanisms are also likely found in relatively low-level human psychology.

The first is imprinting. That is the process in which a newly born animal learns to behave in a special way towards a parent: to follow it around, demand food, etc. Lorenz famously demonstrated the phenomenon by leaving his rubber boots for young geese to see as they hatched. They would then faithfully follow him around the town[1]. The circumstances in which imprinting will occur, and its behavioural consequences, have been extensively described in chicks (Bateson 1966). The mechanism seems to give rise to a new representation: the chick comes to identify and keep track of something new, and behave in various ways in relation to it. The object first presented is clearly part of the cause of this representational development. The representation also seems, intuitively, to refer to that object: it is supposed to keep track of the object first seen[2].

A second example is provided by the cognitive maps that some animals develop as a result of experiencing a local environment (Pearce 1997, pp. 203-214). For example, rats can learn the layout of a maze of platforms hidden underwater, or an array of objects hidden around a room. There is good evidence that this representation is stored in so-called ‘place cells’ in the hippocampus (O’Keefe & Nadel 1978). The new representation is caused by the spatial layout of the environment in which it developed; and, intuitively, represents it.  A particular rat’s cognitive map seems to be about its learning environment, and not other places that happen to have the same geography, or in which the rat’s map-guided actions would turn out to be successful.

A third illustration is aversion learning. This is the striking phenomenon in which an animal will avoid a food if the taste of it is followed by sickness[3]. As in classical conditioning, an UC, sickness, comes to be associated with a CS, the taste. However, unlike classical conditioning, the learning occurs after only one trial, and the aversive stimulus need not be paired in time with the taste, but may occur several hours later.  The substance with that taste is part of the cause of the new aversion[4]. And the new disposition is, intuitively, an aversion to that substance. To test this, consider an animal with its taste buds subsequently reversed by some physiological re-wiring.  The animal would then avoid the wrong things - that is, its aversive representation continues to refer to that which originally caused it.

Finally, consider a regular case of classical conditioning: learning to identify a foodstuff by sight as well as taste.  In primates, it seems this is achieved in part by the development of neurons with finer sensitivity in the orbitofrontal cortex (Rolls & Treves 1998, pp. 155-159). The new representation is caused to develop by the foodstuff with that smell and taste. Plausibly, the referent of the representation is that foodstuff[5].

None of these examples is revolutionary.  Doubtless, many other theories could make good claims for rival content assignments. However, the examples have a common thread, which suggests a special role for an ontogenetic factor, both as the causal source of a new representation, and as its referent. More modestly, they illustrate that it is at least plausible that the circumstances in which a representation developed constrain the content that is to be ascribed to it.

III.    Examples: human learning

There is strong evidence that humans have a specialised capacity for recognising faces.[6] The first indications came from the existence of patients with a selective deficit in the ability to recognise faces, prosopagnosia (Sacks 1985). There are now several converging lines of evidence that face recognition is performed by a dedicated system in the brain. Neuropsychological studies show that damage to a specific brain area is associated with severe prosopagnosia. That has been confirmed with functional imaging, and by electrical measurement and stimulation inside the brains of epileptic patients.[7] The area specific to faces is called the fusiform face area, located near the junction of the brain’s occipital and temporal lobes (although many other brain areas are also involved in processing faces, including prefrontal areas). On experiencing a novel face a person develops the ability to produce a new representation (which is at least partly located in the fusiform face area, and is distributed across that area), which she employs in recognising that face in the future.

It seems obvious that this mechanism’s function is to enable people to recognise each other by their faces. It is part of the way that humans keep track of conspecific individuals. So the representation refers to an individual: the person who caused that representation to develop (call him ‘S’, for source). A different individual, experienced in unusual visual conditions, could later cause the same representation to be tokened. It would then misrepresent (that is S would be false). Similarly with look-alikes. We use face recognition to build up a body of knowledge about how we should act towards a person, and about what he will do. It would be a mistake to project these expectations across to a different individual who happened to look very similar. It is not superficial similarity that grounds the projection of attributes from occasion to occasion. It is the fact of encountering the same individual on each occasion (since many attributes of an individual person are stable over time). And the source of that mistake would be a false representation. The error would start when seeing the look-alike and thinking that is S. The content of that thought is false because the face-tracking representation refers to the original individual, and not anyone else.

Similar considerations have been used in the broader context of the philosophy of language to argue that causal history partly determines the content of proper names (Kripke 1972). However, the conclusion is more compelling in the case of face recognition, both because the phenomenon is simpler and better-described, and because the correct answer is more obvious. The evidence is overwhelming that the ability to recognise a particular face arises only as a result of experience, and is implemented by means of an internal representation. It is then hard to resist the conclusion that the particular circumstances in which one of those abilities develops - the person you see when you learn to recognise someone new - partly determine the content of the resultant representation.

The same thing occurs in higher level cognitive systems. Since these systems are less well described and understood, the content ascription is correspondingly more contentious. I will take as an example the acquisition of concepts of natural kinds.  There is good evidence that the way children categorise changes dramatically as they grow up. Even when newborn they can keep track of objects, by trajectory and number.[8] Ingenious experiments based on violation of expectancy[9] show that babies soon come to differentiate solid objects from portions of stuffs[10], and then begin to track objects by category (e.g., animate vs. inanimate) until they can eventually differentiate objects at the level of natural kind terms: by species, etc.[11]  By the age of 2-3 years children can categorise a wide range of objects on the basis of what they look like and what they do: their characteristic features. But then there is a dramatic shift. Children stop relying upon a wide range of characteristic features and shift to a smaller core of ‘defining’ features as the basis for their category judgments (Keil, 1989). This shows up in overt category judgements, and in the range of new exemplars to which children will project existing known properties.  It is also found implicitly in the way that children project what they learn about things one can do with members of the category[12]. By 4-5 years old children are very good at penetrating beneath surface appearances (Gelman & Wellman, 1991). Their judgements come to be based more on objects’ insides[13] or, for animals, their lineage[14].  Most strikingly, this “characteristic to defining shift”[15] is much more pronounced in relation to natural kinds than artefacts[16].  With artefacts, there is a more subtle shift towards greater reliance on an object’s function for categorisation.

For my purposes, the importance of the developmental studies is to show that an explanation of children’s deployment of concepts must advert to more than surface appearances. (There is a separate debate about whether children have essentialist beliefs, which is not directly relevant except if one holds that the means of identification associated with a concept determine its content.) If a theorist is to explain the patterns of behaviour of older children and adults, she cannot base her explanation only upon the ways that objects appear.  As the experiments show, it is the reidentification of something underlying that explains how the subject will act on a new instance, and which further properties they will project it to (for example, if the original instance tasted sweet, when a further sample is classified under the same concept C the subject may project the property of sweetness and so think that is a C, that is sweet in relation to the new instance). What is the referent of such a concept?  Let’s answer that by asking what it takes for a subject to be getting it right when he uses the concept in relation to a new instance. The answer is that he must be right that the new object has the property which he projects to it, or affords the action that he performs on it.  For such projections to be justified, there must be something in virtue of which the instance shares those properties with the original samples that he learnt about.  Notice that, to be useful, the property / affordance projected must go beyond the way that the new instance is identified as falling under the category.  Suppose you had to check that a fruit was red, round, crisp and tasty before classifying it as an apple. Then inferring from that’s an apple to that’s tasty, while justified, would not tell you anything new. So the relevant underlying feature must give rise to both the properties used to identify instances and to the non-apparent properties that can thereby usefully be projected. So here is the picture: concepts of natural kinds are employed to project useful properties and affordances from learning samples to novel instances.  For that to work, novel instances must fall within the same category as the learning samples, where membership of that category is the causal source both of the properties the thinker relies upon to identify an instance as falling under the concept, and of the properties a thinker thereby projects to those new instances[17].

Reference depends upon the samples the thinker experienced when he originally developed a concept for the category.  The reference is some feature of those samples which allows him to project knowledge about the original samples to new instances.  Given original samples of a different kind, but with the same surface features, the causal basis for the projection of properties would be different, so the referent would be different. When he uses the new representation in respect of an instance of a different category (e.g., he thinks that is an apple, eat it, on seeing a wax apple), then the error consists in identifying the wrong thing - something that does not share a projective ground with the original learning samples. The fact that this new use is a misrepresentation shows that the natural kind concept is tied to the learning samples.  Thus, its referent depends in part upon the particular circumstances in which the concept developed.

The picture I have painted is closely related to Millikan’s (2000) theory of substance concepts.  In particular, I draw from her the idea that use of these sorts of concepts depends upon projecting learned properties to novel instances. That entails that members of the category share some underlying ground that is the causal source of the projected properties.  It is these underlying grounds which Millikan calls ‘substances’: they are the causal source of the co-projection of a variety of properties over instances. However, I rely on developmental considerations more explicitly than Millikan does.  I use the idea that a new substance concept will develop as a result of experience of samples of the substance. Then the reference of the concept will depend upon the identity of those learning samples. Millikan can allow something similar.  Her substance concepts are abilities to identify substances. The reference of the concept is given by its natural purpose: the function of the ability is to identify some particular substance, and that substance is the referent of the concept. Millikan’s natural purposes are given by natural selection. However, most identification abilities have not evolved directly, but are produced in the course of experience by relational mechanisms which have evolved to produce such abilities[18]. Their functions derive from the function of the learning mechanism. The function of the learning mechanism is relational: to produce new abilities that function thus and so. The new abilities so produced derive their function thereby. I emphasise a further feature which Millikan can readily accept: when a general learning mechanism operates in a particular situation to produce a new substance concept, features of that situation determine the function of that ability, and hence the content of the concept. That is perfectly compatible with Millikan’s theory of relational and derived functions, and may even follow from it. If so, Millikan’s theory of substance concepts also supports my claim that the samples which are experienced when a new natural kind concept develops partly constrain the content of that concept.

IV.    Development constraining content

In an important paper Laurence & Margolis (2002) argued for a weaker claim: that an adequate theory of the content of mental representations must be compatible with plausible accounts of how those mental representations arose in psychological development. Their project is to reject Fodor’s strong concept nativism. They start by re-construing Fodor’s nativism as a challenge: how can primitive (i.e., unstructured) representations be learned? Lacking an answer, Fodor concludes they must be innate.  Laurence & Margolis disagree. They argue that there are plausible theories of the acquisition of new primitive representations; i.e. accounts that do not require the new representations to be structured out of existing ones. They take the learning of new natural kind concepts as an example, and work through an empirically justified account of their acquisition[19].

The challenge is to fit the development with the theory of content. Laurence & Margolis take content to be determined by information connections (they work with Fodor’s asymmetric dependence theory of content). The developmental account must show how the end state comes to display the appropriate features, so that content is appropriately determined by the theory of content. The challenge is to demonstrate compatibility between means of acquisition and the theory of content.  It is not simply that it would be nice to have an account of how the representational states are acquired. The constraint is stronger. An adequate theory of content must be compatible with the appropriate content-determining factors being acquirable, according to plausible accounts of development, based on the best empirical evidence.

Of course, one way that the theory of content could be compatible with the developmental story is if developmental circumstances partly determine content. That is my claim. The thrust of Laurence & Margolis’ argument comes close to that stronger suggestion:

“For the present purposes, however, the crucial point we want to emphasize is … that questions about the nature of concepts are intimately bound up with questions about how they are acquired. (...) So even with primitive concepts, an investigation into how they are acquired seems likely to say quite a lot about their nature.”

(Laurence & Margolis 2002, p. 50.)

I agree that the nature of representations is intimately bound up with how they are acquired. That intimacy, I suggest, may be reflected in their contents, such that a representation would not have the content it does if it had not been acquired in the circumstances it was.

Where I disagree with Laurence & Margolis, however, is with their assumption that the development of the vehicles of content is less problematic. They assume that potential vehicles of content are available, the properties of which can be adjusted in content-relevant ways, so that a vehicle comes to have the features which determine its content appropriately (in Laurence & Margolis’ case, being the appropriate informational relations). Thus, as part of their account of the acquisition of natural kind concepts, they say:

“She sees a new object that has features that suggest that it is a natural object of some sort. … upon encountering the item, the child releases a new mental representation and begins accumulating information about the object and linking this to the representation.”

(Laurence & Margolis 2002, p. 42, italics added.)

More likely, part of the process of developing a new concept is to develop a new item which can be the vehicle of that content. Laurence & Margolis agree that the representation has to develop properties appropriate to its content.  What they miss is that this very process may be what differentiates the representation into a new vehicle type. If so there is good reason to add to the scope of Laurence & Margolis’ claim.  Not only must a theory of content be consistent with a semantic account of representational development. It must also be consistent with an account of the development of the vehicles of content. Indeed, the two may be inseparable. In cases where content is partly determined by the circumstances of development of a new representation type, the two together furnish a substantive developmental constraint on an adequate theory of content.

Nicholas Shea

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