Levels of Description & Mental Modules

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Levels of Description & Mental Modules

Levels of Description

&

Mental Modules


Follow-up on questions raised last week:

1) Would Searle allow that a computer that modelled the

neurochemical processes of the brain might have real

intentionality (i.e. might really think)?

No, because only the brain has the right kind of causal

powers.

See the Scientific American article by Searle.


2) According A

to a functional

definition of a process, does

the same input always yield

the same output?

Not necessarily. Might be a

range of appropriate outputs.

Pseudo-random generator.

E.g. roulette wheel, dice

E.g. ALICE


Levels of Description

Processes can be explained at different levels of

description

E.g. How does a car work?

Explain to a user vs. explain to a mechanic vs.

explain to a physics student


Three levels of description:

1) Environmental level (also called intentional level): what does

the thing do? What are the externally observable inputs and

outputs (engineering: black box)? What are its capacities and

limitations?

2) Computational level (also called design level or algorithmic

level): how does the thing work? What method is used to give

certain outputs to certain inputs? What is the internal

organization (engineering: white box)? What are the inputs and

outputs of its internal states?

3) Physical level: : How are the processes physical realized? How

can its workings be described as the actions of physical laws

on physical materials?


Example: multiplication by calculator vs. mind

Calculator

Mind

Environmental level

multiplication

multiplication

14 x 5 = 70 14 x 5 = 70

Computational level

repetitive addition

memorize

14 + 14 + 14 + 14 + 14 multiplication table,

do carrying

14

x 5

Physical level

silicon chip, 1s and 0s

neurons

firing


Each level of description supervenes on the lower level.

What a calculator does (e.g. multiplication) depends on its

program (e.g. repetitive addition) which depends on its

physical make-up

What the brain does (i.e. think) depends on its

organization and computational processes which

depend upon its physical make-up


Cognitive science and the three levels

Cognitive science focuses on the computational level of description

ion

Why?

The environmental level is the view from outside. We can see what

the brain does, what we want to know is how it does it. But

learning the brain’s s capacities and limitations does help us to figure

out what processes are involved.

The physical level is not very interesting. The mind could be realized

in a different physical form (multiple realizability).

Also, physical level has too fine granularity and is too complicated.

Can hardly meaningfully explain a brain in terms of action of

molecules, or even firing of neurons.

However, learning about the physical level helps to understand the t

capacities and limitations of the brain.


Levels within levels

But, there is not just one computational level.

The distinction between levels is sometimes unclear.

There are levels within levels.

The organization of the internal functional modules is a

computational description of the whole brain

The organization of smaller functional units of a functional

module is a computational description of that functional module

The organization of sub-routines within a functional unit is a

computational level description of that functional unit


Each module, functional unit or sub-routine can itself be

described at an environmental level, a computational

level or a physical level, e.g. what does this functional

unit do (in relation to other functional units of the

brain/module), how does it do it, and how is its

operation physically realized?

Attempts to describe the brain at a computational level

can zoom in or zoom out to focus on different levels of

detail.


Homuncular functionalism

One attempt to describe the

functional architecture of the brain.

Homunculus: little man in the brain

Originally, a characterization of

Descartes’ idea that the mind was

situated in the brain (like a little

man) doing the thinking, receiving

inputs and sending out outputs.

Also called the Cartesian theatre

fallacy (“fallacy” because of infinite

regress when again considering the

brain of the little man and so on).


Cognitive science use of the word “homunculus” refers to

autonomous functional units of the brain.

Homuncular functionalism is the attempt to describe the

operation of the brain in terms of (computational-level

level

descriptions of) the interaction of smaller and smaller

units, until the most basic units can be explained in

simple, mechanistic terms (ideally, explainable at a

physical level of description).

Undischarged homunculi: any homunculus that is posited

but whose internal workings are not broken down into

more basic levels of explanation.

Undischarged homunculi are a problem for any

description of the brain.


We want to avoid resorting to “miracles” in explaining the mind.


Modularity of Mind

A computational level description of the mind involves

describing the mind’s s functional architecture, i.e. how

the different functions of the mind are carried out by

different structures of the brain.

The mind can be described as organized into different

functional modules, i.e. different functionally distinct

faculties.


Phrenology

Precursor to theory of

mental modules

Popular in 19 th century

Specific mental faculties

associated with particular

locations in the brain

Mental abilities and

personality could be read

off from bumps on the

head


Modern theory of mental modules put

forward by Jerry Fodor in 1983.

Different parts of the brain are specialized in

the performing of different types of function.


Modules: a division of labor in the brain.

Unlike in phrenology, the modules do not have to occupy

a specific location – they can be spread out over different

areas of the brain


The clearest example of

modularity in the brain.

“Basic” modules.

Vision, hearing, smell

touch and taste

perception are each

handled by distinct

specialized areas of the

brain.

Perception modules


Characteristics of modules

According to Fodor, a specialized faculty of the mind must

meet the following criteria in order to be true modules:

1) Domain specificity

2) Inaccessibility

3) Informational encapsulation, modules need not refer to

other psychological systems in order to operate

4) Automatic

5) Fast

6) Innate

7) Fixed neural architecture.


1) Domain specificity: modules are specialized and only

operate on one kind of input, e.g. the vision module

only operates on visual input – it does not respond to

input from other sensory organs or from other parts of

the brain.

2) Inaccessibility: you cannot perceive the internal

workings of a module, e.g. you cannot look into your

mind and find out how your visual system works. You

can only perceive the output, e.g. you just see a scene in

front of you


3) Information encapsulation: A module cannot be

affected by input from other parts of the brain. Your

visual perception is not affected by what you hear or

feel or know.

Illustrated by the perseverance of optical illusions. Your

visual system does not correct an optical illusion, even

when you know that it is an illusion.

E.g. the Müller-Lyer

illusion


More illusions

See animated version at:

http://library.thinkquest.org/05aug/01744/shepard_tabletop_illusion.htm


4) Automatic: modules perform their function

automatically and it is impossible to turn off the function,

e.g. if someone brings a hot fried chicken into class, you

cannot decide not to smell it (unfortunately)

5) Fast: modules work extremely fast, so, for example, you

appear to sense things immediately. You are unaware of

any delay between opening your eyes and seeing the

world.

6) Innate: the capacities of a module are inborn, and not

developed through experience

7) Fixed neural architecture: there are particular neural

systems associated with particular modules


Modules within modules

Modules can very often be broken down to sub-modules.

e.g. the visual system appears to contain the following

modules:

• Color processing module

• Form processing module

• Motion processing module


Evidence for modularity

1) Neural imaging, e.g. fMRI (functional Magnetic

Resonance Imaging) scans, show distinct structures of

the brain are active when subjects are engaged in

certain tasks. E.g.: Regions in the lateral temporal

association cortex light up when subjects engage in an

object recognition task.

An fMRI scan


2) Brain injuries. An injury (or lesion) in a certain region

of the brain results in characteristic problems, e.g.

injury in the right side temporal lobe results in the

inability to recognize objects (visual agnosia). A

patient with this problem can describe the visual

appearance of an object, and yet not know what it is.

In “The Man who Mistook his Wife for a Hat” by

Oliver Sacks, a man with visual aphasia was handed a

rose. He described it as the object as “a a convoluted

red form with a linear green attachment”, , but was

unable to recognize it as a rose.


3) Dissociation

Single Dissociation:

Lesion in brain structure A disrupts function X but not function Y.

Allows one to infer that functions X and Y are partially independent.

dent.

Grailog (using ‘blank node’ for unnamed instance):

Classes

Thing

subClassOf

Lesion

Brain Structure

Function

pairwiseDisjoint

instanceOf

loc

A

disrupt

X

unequal

Instances

disrupt

Y

negation

loc hasLocation


Double Dissociation:

Lesion in brain structure A disrupts function X but not function Y.

Lesion in brain structure B disrupts function Y but not function X.

Allows one to infer that functions X and Y are mostly independent.

Grailog: analogous


Face recognition module

The form recognition module itself contains at least one

sub-module: the face recognition module.

Double dissociation:

Some people have a deficit (called prosopagnosia or face

blindness) in function X = face recognition, , but are good in

function Y = object recognition. . (People with face blindness

can recognize friends and acquaintances by other visual cues,

e.g. haircut, glasses, body shape, etc.)

Fewer people have a deficit in function Y = object recognition,

but are good in function X = face recognition.

The brain region A = face area and a region that could be called

B = object area might be involved in those deficits

Noam Sagiv: Understanding Face Blindness

http://sciencereview.berkeley.edu/articles.php?issue

sciencereview.berkeley.edu/articles.php?issue=1&article=briefs_3


Modules vs. Central Processsing

According to Fodor, the brain is divided into two types of functional unit:

modules and the central processing system.

Modules are automatic, fast-acting, acting, unconscious. (Parts of Freud’s s Id?)

The central processing system is slow, voluntary and conscious.

(Analogous to Freud’s s Ego?)

Modules present results of internal processing to the central processing

system. The central processing system has access to the inputs of many

systems, and takes care of the logical relations between the various

contents and inputs and outputs.

The operation of the central processing system is what you experience.

You see and hear the results of the visual and auditory modules, you

compare this perception to input from your memory, your imagination,

ion,

etc. and form conclusions, make decisions, etc.


Modules

Central processing

Domain specific

Inaccessible

Informationally

encapsulated

Fast

Automatic

Innate

Global

Accessible

Not informationally

encapsulated

Slow

Voluntary

Affected by learning


(Formal) Ontology:

Ontologies

Shared knowledge conceptualization

(using a logical formalization)

Overview:

http://en.wikipedia.org/wiki/Strong_ontology

Special cases:

Taxonomy: Only subclass-superclass conceptualizations

Partonomy: Only subpart-superpart conceptualizations


Brain ontologies

An OWL ontology enriched with rules for brain anatomical structures

was developed at the University of Rennes, France

Ammar Mechouche, Christine Golbreich, Bernard Gibaud:

Semantic description of brain MRI images

http://image.ntua.gr/swamm2006/resources/paper13.pdf

Within the Foundational Model of Anatomy (FMA) Ontology,

a Protege partonomy for brain anatomy was developed at the

University of Washington, Seattle, USA

Jose Mejino et al.: Challenges in Reconciling Different Views of

Neuroanatomy in a Reference Ontology of Anatomy

http://sigpubs.biostr.washington.edu/archive/00000214/


Brain ontologies (cont.)

Exploration of Foundational Model of Anatomy's brain partonomy

hasPart

http://www.na-mic.org/Wiki/index.php/Image:Fma.JPG


Brain ontologies (cont.)

BrainML (http://www.brainml.org) is an evolving standard

XML metaformat to exchange neuroscience data and models.

It includes a partonomy for neural structure / anatomy:

http://www.brainml.org/viewVocabulary.do?versionID=786

CNS [central nervous system]

brain

forebrain

cerebral cortex

frontal lobe/area

CMA [cingulate motor area]

dorsal prefrontal cortex

F1/MI [primary motor area]

F2/F7 PMd [premotor area (dorsal)]

F3/F6 SMA/preSMA [(pre-)supplementary motor area]

F4/F5 PMv [premotor area (ventral)]

lateral prefrontal cortex

[FEF] frontal eye fields

medial prefrontal cortex

MEF/SEF [medial eye field, supplemental eye field]

orbitofrontal cortex

parietal lobe/area

. . .


Readings

Optional readings:

Sterelny, , Kim, The Representational Theory of Mind, , Chapter 2, pgs. 19-41

More optional readings:

Pinker, Stephen, The Language Instinct, , Ch. 3 “Mentalese”,, pgs. 55-82.

Review by Mark Alford, 2000. http://alford.fastmail.us/pinker.html

Dennett, Daniel, Brainstorms, , Ch. 6 “A A Cure for the Common Code”, , pgs. 90-

108. http://cognet.mit.edu/library/books/view?isbn

cognet.mit.edu/library/books/view?isbn=0262540371

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