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These are excerpts and elaborations from my book "The Nature of Consciousness"
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Mental Models The British psychologist
Philip Johnson-Lairdhas questioned both the
plausibility and the adequacy of a cognitive model based on production rules. A
mind that only used production rules, i.e. Logic, would behave in a
fundamentally different way from ours. People often make mistakes with
deductive inference because it is not a natural way of thinking. The natural
way is to construct mental models of the premises: a model of discourse has a
structure that corresponds directly to the structure of the state of affairs
that the discourse describes. For the
same reason children are able to acquire inferential capabilities before they
have any inferential notions: children solve problems by building mental models
that are more and more complex, not by applying the rules of classical Logic
(that they have not learned yet). In his view, the mind
represents and processes models of the world. The mind solves problems without
any need to use logical reasoning. A
sentence is a procedure to build, modify, extend a mental model. The mental model created by a discourse
exhibits a structure that corresponds directly to the structure of the world
described by the discourse. To perform
an inference on a problem the mind needs to build the situation described by
its premises. Such mental model simplifies reality and allows the mind to find
an "adequate" (not necessarily exact) solution. Johnson-Laird's theory admits three types
of representation: "propositions" (which represent the world through
sequences of symbols), "mental models" (which are structurally
analogous to the world) and "images" (which are perceptive correlates
of models). Images are ways to approach models. They represent the perceivable
features of the corresponding objects of the real world. Models, images and propositions are
functionally and structurally different.
Linguistic expressions are first transformed into propositional
representations. The semantics of the
mental language then creates correspondences between propositional
representations and mental models, i.e. propositional representations are
interpreted in mental models. But
the key to understanding how the mind works is in the mental models. The French linguist Gilles
Fauconnieradvocates a similar vision in
his theory of "mental spaces". Mental spaces proliferate as we think
or talk. The mappings that link mental spaces, especially analogical mappings,
play a central role in building our mental life. In particular,
"conceptual blending" is a cognitive process which can be detected in
many different cognitive, cultural and social activities. By merging different
inputs, it creates a blended mental space that lends itself to what we call
"creative" thinking. Therefore,
Fauconnierfinds that the same principles that operate at the level of
meaning construction operate also at the level of scientific and artistic
action. The US linguist George
Lakoffhas given mental spaces an
internal structure with his theory of "idealized cognitive models that
are embodied, i.e. they are linked with bodily experience. Mental Imagery "Mental imagery"
is seeing something in the absence of any sensory signal, such as visualizing
an object that is not actually present. The mystery is what is seen if in the
brain there is no such image. When I stare at an object, i see the image that
the visual system creates in the brain (whatever projection of dots through the
retina to this or that region of the brain). But am i seeing when i am simply
imagining a Ferrari? Scientists have found no
pictures or images in the brain, no internal eye to view pictures stored in
memory and no means to manipulate them. Nevertheless, there is an obvious
correspondence between a mental image of an object and the object. The US psychologist Ronald
Finke, for example, has identified five principles of equivalence between a
mental image and the perceived object: the principle of implicit encoding
(information about the properties of an object can be retrieved from its mental
image), the principle of spatial equivalence (parts of a mental image are
arranged in a way that corresponds to the way that the parts of the physical object
are arranged), the principle of perceptual equivalence (similar processes are
activated in the brain when the objects are imagined as when they are
perceived), the principle of transformational equivalence (imagined transformations and physical transformations
are governed by the same laws of motion), the principle of structural
equivalence (the mental imagery exhibits structural features corresponding to
those of the perceived object such that the relations between the object's
parts can be both preserved and interpreted). During the 1980s the debate
became polarized around two main schools of thought: either (The US
psychologist Stephen Kosslyn) the brain maintains mental pictures that somehow represent the
real-world images, or (the US psychologist Zenon Pylyshyn) the brain represents images through a non-imaginistic system,
namely language, i.e. all mental representations are descriptive and not
pictorial (there are no picture-like representations in the brain). Kosslynput forth a representational
theory of the mind of a "pictorial" type, as opposed to Jerry Fodor's propositional theory and related to Philip Johnson-Laird's mental models. Kosslyn
thinks that the brain builds visual representations, which are coded in parts
of the brain, and which reflect what they represent. Mental imagery involves
scanning an internal picture-like entity. Mental images can be inspected and classified
using pretty much the same processes used to inspect and classify visual
perceptions. For example, they can be
transformed (rotated, enlarged, reduced).
There exist two levels of
visual representation: a "geometric" level, which allows one to mentally
manipulate images, and an "algebraic" one, which allows one to
"talk" about those images. Kosslynthinks that mental imagery
achieves two goals: retrieve properties of objects, and predict what would
happen if the body or the objects should move in a given way. Reasoning on
shapes and dimensions is far faster when we employ mental images than
concepts. Kosslyn's is a theory of high-level vision in which perception and
representation are inextricably linked. Visual perception (visual object
identification) and visual mental imagery share common mechanisms. Opposed to Kosslyn's pictorialism is Pylyshyn's "descriptionalism". Pylyshyn believes in a variant of
Fodor's language of thought: to him images are simply the product of the
manipulation of knowledge encoded in the form of propositions. The dual coding theory of
the Canadian psychologist Allan Paivio mediates these positions because it
argues that the mind may use two different types of representation, a verbal
one and a visual one, corresponding to the brain's two main perceptive
systems. They both "encode"
memories, but they do so in different ways (codes). The neural processes that
correspond to mental imagery in seeing people have also been detected in the
brains of congenitally blind people. Thus mental imagery cannot possibly depend
on forming a mental reconstruction of former visual sense experiences. Back to the beginning of the chapter "Cognition: A General Property of Matter " | Back to the index of all chapters |
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