Levels of DescriptionLevels of Description

&&

Mental ModulesMental Modules

Follow-up on questions raised last week: Follow-up on questions raised last week:

1)1) Would Searle allow that a computer that Would Searle allow that a computer that modelled the neurochemical processes of modelled the neurochemical processes of the brain might have real intentionality the brain might have real intentionality (i.e. might really think)? (i.e. might really think)?

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

See the Scientific American article by See the Scientific American article by Searle.Searle.

2) A2) According to a ccording to a functional definition of a functional definition of a process, does the same process, does the same input always yield the input always yield the same output?same output?

Not necessarily. Might Not necessarily. Might be a range of be a range of appropriate outputs.appropriate outputs.

Pseudo-random Pseudo-random generator.generator.

E.g. roulette wheel, diceE.g. roulette wheel, diceE.g. ALICEE.g. ALICE

Levels of DescriptionLevels of Description

Processes can be explained at Processes can be explained at different levels of descriptiondifferent levels of description

E.g. How does a car work?E.g. How does a car work?

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

Three levels of description:Three levels of description:

1)1) Environmental levelEnvironmental level (also called intentional (also called intentional level): what does the thing do? What are the level): what does the thing do? What are the externally observable inputs and outputs externally observable inputs and outputs (engineering: black box)? What are its capacities (engineering: black box)? What are its capacities and limitations?and limitations?

2)2) ComputationalComputational levellevel (also called design level or (also called design level or algorithmic level): how does the thing work? algorithmic level): how does the thing work? What method is used to give certain outputs to What method is used to give certain outputs to certain inputs? What is the internal organization certain inputs? What is the internal organization (engineering: white box)? What are the inputs (engineering: white box)? What are the inputs and outputs of its internal states?and outputs of its internal states?

3)3) PhysicalPhysical levellevel: How are the processes physical : How are the processes physical realized? How can its workings be described as realized? How can its workings be described as the actions of physical laws on physical the actions of physical laws on physical materials? materials?

CalculatorCalculator MindMind

Environmental levelEnvironmental level multiplicationmultiplicationmultiplicationmultiplication 14 x 5 = 7014 x 5 = 70 14 x 5 = 7014 x 5 = 70

ComputationalComputational levellevelrepetitive additionrepetitive addition memorizememorize14 + 14 + 14 + 14 + 1414 + 14 + 14 + 14 + 14

multiplication table,multiplication table, do carryingdo carrying

1414 x 5x 5

PhysicalPhysical levellevel silicon chip, 1s and 0ssilicon chip, 1s and 0s neuronsneurons firingfiring

Example: multiplication by Example: multiplication by calculator vs. mindcalculator vs. mind

Each level of description supervenes on the Each level of description supervenes on the lower level.lower level.

What a calculator does (e.g. multiplication) What a calculator does (e.g. multiplication) depends on its program (e.g. repetitive depends on its program (e.g. repetitive addition) which depends on its physical addition) which depends on its physical make-upmake-up

What the brain does (i.e. think) depends on What the brain does (i.e. think) depends on its organization and computational its organization and computational processes which depend upon its physical processes which depend upon its physical make-up make-up

Cognitive science and the three Cognitive science and the three levelslevels

Cognitive science focuses on the computational level of Cognitive science focuses on the computational level of descriptiondescription

Why?Why?

The environmental level is the view from outside. We can The environmental level is the view from outside. We can see see whatwhat the brain does, what we want to know is the brain does, what we want to know is howhow it does it. But learning the brain’s capacities and it does it. But learning the brain’s capacities and limitations does help us to figure out what processes limitations does help us to figure out what processes are involved.are involved.

The physical level is not very interesting. The mind could The physical level is not very interesting. The mind could be realized in a different physical form (multiple be realized in a different physical form (multiple realizability).realizability).Also, physical level has too fine granularity and is too Also, physical level has too fine granularity and is too complicated. Can hardly meaningfully explain a brain in complicated. Can hardly meaningfully explain a brain in terms of action of molecules, or even firing of neurons.terms of action of molecules, or even firing of neurons.However, learning about the physical level helps to However, learning about the physical level helps to understand the capacities and limitations of the brain.understand the capacities and limitations of the brain.

Levels within levelsLevels within levels

But, there is not just one computational level.But, there is not just one computational level.

The distinction between levels is sometimes unclear.The distinction between levels is sometimes unclear.

There are levels within levels.There are levels within levels.

The organization of the internal functional modules is a The organization of the internal functional modules is a computational description of the whole braincomputational description of the whole brain

The organization of smaller functional units of a functional The organization of smaller functional units of a functional module is a computational description of that functional module is a computational description of that functional modulemodule

The organization of sub-routines within a functional unit is The organization of sub-routines within a functional unit is a computational level description of that functional unita computational level description of that functional unit

Each module, functional unit or sub-routine Each module, functional unit or sub-routine can itself be described at an can itself be described at an environmental level, a computational level environmental level, a computational level or a physical level, e.g. what does this or a physical level, e.g. what does this functional unit do (in relation to other functional unit do (in relation to other functional units of the brain/module), how functional units of the brain/module), how does it do it, and how is its operation does it do it, and how is its operation physically realized?physically realized?

Attempts to describe the brain at a Attempts to describe the brain at a computational level can zoom in or zoom computational level can zoom in or zoom out to focus on different levels of detail.out to focus on different levels of detail.

Homuncular functionalismHomuncular functionalism

One attempt to describe the One attempt to describe the functional architecture of the functional architecture of the brain.brain.

Homunculus: little man in the brainHomunculus: little man in the brain

Originally, a characterization of Originally, a characterization of Descartes’ idea that the mind was Descartes’ idea that the mind was situated in the brain (like a little situated in the brain (like a little man) doing the thinking, man) doing the thinking, receiving inputs and sending out receiving inputs and sending out outputs. Also called the outputs. Also called the Cartesian theatre fallacyCartesian theatre fallacy (“fallacy” because of infinite (“fallacy” because of infinite regress when again considering regress when again considering the brain of the little man and so the brain of the little man and so on).on).

Cognitive science use of the word “homunculus” Cognitive science use of the word “homunculus” refers to autonomous functional units of the refers to autonomous functional units of the brain.brain.

Homuncular functionalism is the attempt to Homuncular functionalism is the attempt to describe the operation of the brain in terms of describe the operation of the brain in terms of (computational-level descriptions of) the (computational-level descriptions of) the interaction of smaller and smaller units, until interaction of smaller and smaller units, until the most basic units can be explained in simple, the most basic units can be explained in simple, mechanistic terms (ideally, explainable at a mechanistic terms (ideally, explainable at a physical level of description).physical level of description).

Undischarged homunculi: any homunculus that is Undischarged homunculi: any homunculus that is posited but whose internal workings are not posited but whose internal workings are not broken down into more basic levels of broken down into more basic levels of explanation. explanation.

Undischarged homunculi are a problem for any Undischarged homunculi are a problem for any description of the brain.description of the brain.

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

Modularity of MindModularity of Mind

A computational level description of the A computational level description of the mind involves describing the mind’s mind involves describing the mind’s functional architecture, i.e. how the functional architecture, i.e. how the different functions of the mind are carried different functions of the mind are carried out by different structures of the brain.out by different structures of the brain.

The mind can be described as organized The mind can be described as organized into different functional modules, i.e. into different functional modules, i.e. different functionally distinct faculties. different functionally distinct faculties.

PhrenologyPhrenology

Precursor to theory of mental modules

Popular in 19th 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 Modern theory of mental modules put forward by Jerry Fodor in put forward by Jerry Fodor in 1983.1983.

Different parts of the brain are Different parts of the brain are specialized in the performing of specialized in the performing of different types of function.different types of function. Modules: a division of labor in the brain.Modules: a division of labor in the brain.

Unlike in phrenology, the modules do not Unlike in phrenology, the modules do not have to occupy a specific location – have to occupy a specific location – they can be spread out over different areas of they can be spread out over different areas of the brainthe brain

Perception modulesPerception modules

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.

Characteristics of modulesCharacteristics of modules

According to Fodor, a specialized faculty of the mind According to Fodor, a specialized faculty of the mind must meet the following criteria in order to be true must meet the following criteria in order to be true modules:modules:

1)1) Domain specificityDomain specificity2)2) InaccessibilityInaccessibility3)3) Informational encapsulation, modules need not Informational encapsulation, modules need not

refer to other psychological systems in order to refer to other psychological systems in order to operate operate

4)4) AutomaticAutomatic5)5) FastFast6)6) InnateInnate7)7) Fixed neural architecture. Fixed neural architecture.

1)1) Domain specificity:Domain specificity: modules are modules are specialized and only operate on one kind specialized and only operate on one kind of input, e.g. the vision module only of input, e.g. the vision module only operates on visual input – it does not operates on visual input – it does not respond to input from other sensory respond to input from other sensory organs or from other parts of the brain.organs or from other parts of the brain.

2)2) Inaccessibility:Inaccessibility: you cannot perceive you cannot perceive the internal workings of a module, e.g. the internal workings of a module, e.g. you cannot look into your mind and find you cannot look into your mind and find out how your visual system works. You out how your visual system works. You can only perceive the output, e.g. you just can only perceive the output, e.g. you just see a scene in front of yousee a scene in front of you

3)3) Information encapsulation:Information encapsulation: A A module cannot be affected by input from module cannot be affected by input from other parts of the brain. Your visual other parts of the brain. Your visual perception is not affected by what you hear perception is not affected by what you hear or feel or know. or feel or know.

Illustrated by the perseverance of optical Illustrated by the perseverance of optical illusions. Your visual system does not correct illusions. Your visual system does not correct an optical illusion, even when you know that an optical illusion, even when you know that it is an illusion.it is an illusion.

E.g. the Müller-Lyer illusionE.g. the Müller-Lyer illusion

More illusionsMore illusions

See animated version at: http://library.thinkquest.org/05aug/01744/shepard_tabletop_illusion.htm

4)4) Automatic:Automatic: modules perform their function modules perform their function automatically and it is impossible to turn off the automatically and it is impossible to turn off the function, e.g. if someone brings a hot fried chicken function, e.g. if someone brings a hot fried chicken into class, you cannot decide not to smell it into class, you cannot decide not to smell it (unfortunately)(unfortunately)

5)5) Fast:Fast: modules work extremely fast, so, for example, modules work extremely fast, so, for example, you appear to sense things immediately. You are you appear to sense things immediately. You are unaware of any delay between opening your eyes and unaware of any delay between opening your eyes and seeing the world.seeing the world.

6)6) Innate:Innate: the capacities of a module are inborn, and the capacities of a module are inborn, and not developed through experiencenot developed through experience

7)7) Fixed neural architecture:Fixed neural architecture: there are particular there are particular neural systems associated with particular modulesneural systems associated with particular modules

Modules within modulesModules within modules

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

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

• Color processing moduleColor processing module• Form processing moduleForm processing module• Motion processing moduleMotion processing module

Evidence for modularityEvidence for modularity1)1) Neural imaging, e.g. fMRI (functional Neural imaging, e.g. fMRI (functional

Magnetic Resonance Imaging) scans, show Magnetic Resonance Imaging) scans, show distinct structures of the brain are active distinct structures of the brain are active when subjects are engaged in certain when subjects are engaged in certain tasks. E.g.: Regions in the lateral temporal tasks. E.g.: Regions in the lateral temporal association cortex light up when subjects association cortex light up when subjects engage in an object recognition task.engage in an object recognition task.

An fMRI scan

2)2) Brain injuries. An injury (or lesion) in a certain Brain injuries. An injury (or lesion) in a certain region of the brain results in characteristic region of the brain results in characteristic problems, e.g. injury in the right side temporal problems, e.g. injury in the right side temporal lobe results in the inability to recognize objects lobe results in the inability to recognize objects (visual agnosia). A patient with this problem (visual agnosia). A patient with this problem can describe the visual appearance of an can describe the visual appearance of an object, and yet not know what it is.object, and yet not know what it is.

In “The Man who Mistook his Wife for a Hat” In “The Man who Mistook his Wife for a Hat” by Oliver Sacks, a man with visual aphasia was by Oliver Sacks, a man with visual aphasia was handed a rose. He described it as the object as handed a rose. He described it as the object as “a convoluted red form with a linear green “a convoluted red form with a linear green attachment”, but was unable to recognize it as attachment”, but was unable to recognize it as a rose.a rose.

3)3) DissociationDissociation

Single Dissociation:Single Dissociation:Lesion in brain structure A disrupts function X but not Lesion in brain structure A disrupts function X but not function Y.function Y.Allows one to infer that functions X and Y are partially Allows one to infer that functions X and Y are partially independent.independent.

X

Y

disruptdisrupt

disruptdisrupt

LesionLesion FunctionFunctioninstanceOf

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

Brain StructureBrain Structure

Alocloc

locloc hasLocation

ThingThing subClassOf

pairwiseDisjoint

Classes

Instances

negation

unequal

Double Dissociation:Double Dissociation:Lesion in brain structure A disrupts function X but not function Y.Lesion in brain structure A disrupts function X but not function Y.Lesion in brain structure B disrupts function Y but not function X.Lesion in brain structure B disrupts function Y but not function X.Allows one to infer that functions X and Y are mostly independent.Allows one to infer that functions X and Y are mostly independent.

Grailog: Grailog: analogousanalogous

Face recognition moduleFace recognition module

The form recognition module itself contains at least oneThe form recognition module itself contains at least onesub-module: the face recognition module.sub-module: the face recognition module.

Double dissociation:Double dissociation:Some people have a deficit (called prosopagnosia or Some people have a deficit (called prosopagnosia or face blindness) in function X = face blindness) in function X = face recognitionface recognition, but , but are good in function Y = are good in function Y = object recognitionobject recognition. (People . (People with face blindness can recognize friends and with face blindness can recognize friends and acquaintances by other visual cues,acquaintances by other visual cues,e.g. haircut, glasses, body shape, etc.)e.g. haircut, glasses, body shape, etc.)Fewer people have a deficit in function Y = Fewer people have a deficit in function Y = object object recognitionrecognition, but are good in function X = , but are good in function X = face face recognitionrecognition..The brain region A = The brain region A = face areaface area and a region that and a region that could be called could be called B = B = object areaobject area might be involved in those deficits might be involved in those deficits

Noam Sagiv: Understanding Face Blindness Noam Sagiv: Understanding Face Blindness http://http://sciencereview.berkeley.edu/articles.php?issuesciencereview.berkeley.edu/articles.php?issue=1&article=briefs_3=1&article=briefs_3

Modules vs. Central ProcesssingModules vs. Central Processsing

According to Fodor, the brain is divided into two types of According to Fodor, the brain is divided into two types of functional unit: functional unit: modulesmodules and the and the central processing central processing systemsystem..

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

The central processing system is slow, voluntary and conscious.The central processing system is slow, voluntary and conscious.(Analogous to Freud’s Ego?)(Analogous to Freud’s Ego?)

Modules present results of internal processing to the central Modules present results of internal processing to the central processing system. The central processing system has access processing system. The central processing system has access to the inputs of many systems, and takes care of the logical to the inputs of many systems, and takes care of the logical relations between the various contents and inputs and relations between the various contents and inputs and outputs. outputs.

The operation of the central processing system is what you The operation of the central processing system is what you experience. You see and hear the results of the visual and experience. You see and hear the results of the visual and auditory modules, you compare this perception to input from auditory modules, you compare this perception to input from your memory, your imagination, etc. and form conclusions, your memory, your imagination, etc. and form conclusions, make decisions, etc.make decisions, etc.

ModulesModules Central processingCentral processing

Domain specificDomain specific GlobalGlobalInaccessibleInaccessible AccessibleAccessibleInformationallyInformationally Not informationallyNot informationally encapsulatedencapsulated encapsulated encapsulatedFastFast SlowSlowAutomaticAutomatic VoluntaryVoluntaryInnateInnate Affected by learningAffected by learning

OntologiesOntologies

(Formal) Ontology: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 ontologiesBrain ontologies

Jose Mejino et al.: Challenges in Reconciling Different Views ofNeuroanatomy in a Reference Ontology of Anatomyhttp://sigpubs.biostr.washington.edu/archive/00000214/

Ammar Mechouche, Christine Golbreich, Bernard Gibaud:Semantic description of brain MRI imageshttp://image.ntua.gr/swamm2006/resources/paper13.pdf

An OWL ontology enriched with rules for brain anatomical structureswas developed at the University of Rennes, France

Within the Foundational Model of Anatomy (FMA) Ontology,a Protege partonomy for brain anatomy was developed at theUniversity of Washington, Seattle, USA

Brain ontologies (cont.)Brain ontologies (cont.)

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

Exploration of Foundational Model of Anatomy's brain partonomy

hasPart

Brain ontologies (cont.)Brain ontologies (cont.)BrainML (http://www.brainml.org) is an evolving standardXML 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 . . .

ReadingsReadingsOptional readingsOptional readings: :

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

More optional readingsMore optional readings::

Pinker, Stephen, Pinker, Stephen, The Language InstinctThe Language Instinct, Ch. 3 “Mentalese”, , Ch. 3 “Mentalese”, pgs. 55-82.pgs. 55-82.Review by Mark Alford, 2000. Review by Mark Alford, 2000. http://alford.fastmail.us/pinker.htmlhttp://alford.fastmail.us/pinker.html

Dennett, Daniel, Dennett, Daniel, BrainstormsBrainstorms, Ch. 6 “, Ch. 6 “A Cure for the A Cure for the Common CodeCommon Code”, pgs. 90-108. ”, pgs. 90-108. http://cognet.mit.edu/library/books/view?http://cognet.mit.edu/library/books/view?isbn=0262540371isbn=0262540371