Cognition 1 Foundations

Roberto G. de Almeida

Department of Psychology

Concordia University Roberto.deAlmeida@Concordia.ca

http://alcor.concordia.ca/~coglab

Fall 2008

Foundations of Cognitive Science

!!Cognition - a working definition: "! The study of mental representations and

processes involved in the acquisition, storage, retrieval, and use of knowledge.

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What do these figures represent?

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One possible interpretation:

Two similar cubes…different perspectives!

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Assumptions: Your visual system is equipped to extract 3-D information from one arrangement of lines, but not the other…

It relies on certain properties of the

“object” (line arrangements, vertices) and it relies on its own “rules” to assign a global

interpretation to the line drawing !

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“rules”!

y!

“z”!x!

A “3-D from 2-D Rule”

If lines meet at a given

point, interpret as 3-D

vertex of an object A “Grouping by similarity Rule”

Interpret similar objects as having

the same orientation in 3-D

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Types of knowledge

!!Cognition - a working definition:

"! The study of mental representations and processes involved in the acquisition, storage, retrieval, and use of knowledge.

"!Knowledge: explicit or implicit

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!!Knowledge: explicit or implicit

"! Explicit: !! Declarative memory: semantic memory, episodic

memory

#! Semantic: Common knowledge of the world, concepts

#! Episodic: Autobiographical, personal experience, own view (including false memories)

Types of knowledge

(Loftus, 1997) 8

Types of knowledge

!!Knowledge: explicit or implicit

"! Implicit: !! A bunch of things:

#! Whatever enables you to perform cognitive tasks without having to rely on your declarative memory:

#! Procedural-type memory: rules, mechanisms, perceptual knowledge/processes, grammar, etc.

#! Mostly, unlearned (by hypothesis, innate)

#! If learned, automatic (well practiced)

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Representations & processes

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"!Knowledge-based behavior/processes

!!Processes driven by explicit goals, explicit knowledge (semantic/episodic), intentions

John Sloan (1851-1951), “Spring Rain” - Delaware Art Museum

Representations & processes

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Representations & processes

"!Rule-governed behavior/processes

!!Covert processes

!!Processes that rely on implicit knowledge

Claude Lorrain (1600-1682), “A seaport at sunset”, Louvre, Paris 12

The fundamental concepts

"!Representations

!!“Things in the mind that stand for

things in the world”

"!Mental processes

!! Operations over representations

!! “Computations” (or “activations”) of representations

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!! Descartes, Hobbes, Hume: "! Mental Representations are

Ideas, Mental Processes are “Calculations” (Computations)

!! They are “language-like”

!! They are abstract

!! They are symbolic

!! They are the very elements of thoughts, cognitive processes

Mental Representations

Cummins, 1991

[CHAIR]

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Mental Processes as Computation over Representations !! Modern view: Perceptual and cognitive systems

(some) work as a function of the “laws”/”rules” they follow

!! Consider the following:

"! Suppose you know that John is either married to Mary or to Susan.

"! And then suppose you discover that John is not

married to Susan…

"! What can you conclude?

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!!Right! John must be married to Mary

!!We can represent this by equations (with special, logical terms “or” and “not”) "! (1) Married (J, M) or Married (J,S)

"! (2) not [Married (J,S)]

"! (3) therefore, Married (J,M)

Pylyshyn, 1999

Mental Processes as Computation over Representations

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!! Notice that (3) follows from (1) and (2) regardless of the “content” of the parts of the equation (except for or and not)

!! Thus, replacing (1)-(3) by the meaningless letters P

and Q should yield the same effect:

"! (1’) P or Q

"! (2’) not Q

"! (3’) P

!!The process is carried out just in virtue of its form (or syntax or structure)!

–!(1) Married (J, M) or Married (J,S)

–!(2) not [Married (J,S)]

–!(3) therefore, Married (J,M)

Pylyshyn, 1999

Mental Processes as Computation over Representations

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!!The process is carried out just in virtue

of its form (or syntax or structure)!

"! That is: computations over symbolic

representations are operations driven by rules (syntax)

!! We can think of higher-order thought processes (e.g., reasoning)…

!! We can think about computations within specialized cognitive systems - such as Language, Vision…

!! The idea is that behind most perceptual or cognitive processes there are sets of rules governing the processes

Mental Processes as Computation over Representations

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!! Notice that I haven’t talked about the physical device in which those representations and processes are implemented...

E.g.: reading a

word aloud

Levels of Explanation

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!! Notice that I haven’t talked about the physical device in which those representations and processes are implemented...

!! Are our explanations intrinsically dependent on the nature of this physical device?

!! Should we reduce the cognitive explanation to a neurophysiological account of brain states?

!! Would an anatomical classification suffice?

Cognition = Neurophysiology?

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!! Notice that I haven’t talked about the physical device in which those representations and processes are implemented...

!! Are our explanations intrinsically dependent on the nature of this physical device?

!! Should we reduce the cognitive explanation to a neurophysiological account of brain states?

!! Would an anatomical classification suffice?

What is missing, then? How can we account for brain function

(mind) without appealing to neurophysiology or neuroanatomy

alone?

Cognition = Neurophysiology?

No!

No!

No!

!

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Fodor, 1986

Fodor, 1

981

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!!The behaviorist machine: !!One and only one state:

#! For every input (a dime) a response (a Coke)

!!The cognitivist machine: !!Two (or more) possible states:

#!Outputs depend on:

#! 1. Input

#! 2. The machine’s current state given 1

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Functionalism and Cognitive Explanation

!!Machine Functionalism:

!! The behavior of the machine can be explained as a function of

#! the machine’s (internal) states

#! the machine’s causal structure

!! To understand the machine (or human brain, or the Martian’s heart) we have to

understand its internal functions, the “laws” that guide its behavior

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Turing Machine Alan Turing (1912-1954)

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Turing Machine

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Turing Machine !! Machine’s computations (processes):

"! Read symbols from the tape (B, 0, 1)

"! Write symbols on the tape (B, 0, 1)

"! Move (L, R)

!! Machine’s representations: "! Symbols

!! In sum: Machine reads a symbol, writes a symbol, and moves left or right, according to its states specified in the table (the program)

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Turing Machine

!!Key ideas: "!an information processing system (a

physical system) can “behave” just in virtue of its “rules and representations”

"!We can explain behavior (cognitive behavior) by specifying the nature of the rules and representations a system encodes

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Marr’s Three Levels !!Computational theory:

"! The goal of the computation, what it is supposed to be about or to solve (e.g., Attention, Sentence Processing, Object Recognition)

!!Representation and Algorithm: "! Representations that the system manipulates

and how it does it (What types of representations are used, What types of rules, What kinds of processes)

!! Implementation: "! Physical instantiation (the nature of the actual

physical device - e.g., the brain, the computer)

Marr, 1982 30

Cognitive Theorizing

!! The Brain as the “organ” of the Mind

!!Representationalism: Emphasis on Mental Representations

!! Functionalism: emergent properties

!!Different Representationalist Schools: "! Symbolic (Turing-like, computations)

"! Connectionist (“brain-like”, associations)

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