Mind, Body, World- Foundations of Cognitive Science, 2013a

The packing problem is concerned with maximizing the computational power
of a physical device with limited resources, such as a brain with a finite number of
neurons and synapses. How does one pack the maximal computing power into a
finite brain? Ballard (1986) argued that many different subsystems, each designed
to deal with a limited range of computations, will be easier to fit into a finite package
than will be a single general-purpose device that serves the same purpose as all
of the subsystems.
Of course, in order to enable a resource-limited system to solve the same class
of problems as a universal machine, a compromise solution to the packing problem
may be required. This is exactly the stance adopted by Fodor in his influential 1983
monograph The Modularity of Mind. Fodor imagined an information processor
that used general central processing, which he called isotropic processes, operating
on representations delivered by a set of special-purpose input systems that are now
known as modules.
If, therefore, we are to start with anything like Turing machines as models in cognitive
psychology, we must think of them as embedded in a matrix of subsidiary
systems which affect their computations in ways that are responsive to the flow of
environmental events. The function of these subsidiary systems is to provide the
central machine with information about the world. (Fodor, 1983, p. 39)
According to Fodor (1983), a module is a neural substrate that is specialized for
solving a particular information processing problem. It takes input from transducers,
preprocesses this input in a particular way (e.g., computing three-dimensional
structure from transduced motion signals [Hildreth, 1983; Ullman, 1979]), and
passes the result of this preprocessing on to central processes. Because modules
are specialized processors, they are domain specific. Because the task of modules is
to inform central processing about the dynamic world, modules operate in a fast,
mandatory fashion. In order for modules to be fast, domain-specific, and mandatory
devices, they will be “wired in,” meaning that a module will be associated with
fixed neural architecture. A further consequence of this is that a module will exhibit
characteristic breakdown patterns when its specialized neural circuitry fails. All of
these properties entail that a module will exhibit informational encapsulation: it
will be unaffected by other models or by higher-level results of isotropic processes.
In other words, modules are cognitively impenetrable (Pylyshyn, 1984). Clearly any
function that can be shown to be modular in Fodor’s sense must be a component of
the architecture.
Fodor (1983) argued that modules should exist for all perceptual modalities,
and that there should also be modular processing for language. There is a great deal
of evidence in support of this position.
For example, consider visual perception. Evidence from anatomy, physiology,
and clinical neuroscience has led many researchers to suggest that there exist
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