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Cognitive Systems > Cognitive Architectures > Flashcards

Cognitive Architectures Flashcards

- How to implement a cognitive system? - Cognitive Architecture – A Definition - Classification of Cognitive Architectures - Requirements Analysis - ACT-R – A Cognitive Architecture

1
Q

What is a cognitive architecture?

A

A cognitive architecture is a model of a cognitive system that defines the basic and irreducible cognitive operations that enable the human mind.

(In theory, each task that humans can perform should consist of a series of these discrete operations.)

(A cognitive architecture is a theory about the structure of the human mind and to a computational instantiation of such a theory.)

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2
Q

How was the design of cognitive architectures motivated?

A

The design of cognitive architectures was originally motivated in cognitivist cognitive science by Newell’s concept of a unified theory of cognition.

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3
Q

What is a cognitive model?

A

A cognitive model is an instantiation of a cognitive architecture with a specific body of knowledge.

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4
Q

What are the goals of cognitive architectures?

A

Modelling of the human mind

  • advance understanding of cognition through computer-executable description of cognitive processes
  • reproduction of experimental data
  • focus on generality and robustness

Construction of artificial cognitive systems
- design of artificial systems that are as capable as living creatures

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5
Q

What are the advantages of cognitive architectures?

A

Cognitive architectures are…

  • generic and can be applied to different domains
  • unified models that coherently integrate many different aspects of cognition
  • executable implementations of cognition theories
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6
Q

What are the levels of modeling regarding cognitive systems?

A
  • sociological level: interaction between agents
  • psychological level: cognition in individual agents
  • componential level: cognitive architecture
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7
Q

What do cognitivist cognitive architectures model?

A

A cognitivist cognitive architecture models those aspects of cognition that are task-independent and constant over time.

  • specifies only basic components and processes such as memory, knowledge
  • generic model that reflects a specific set of assumptions
  • the architecture is a framework that does not include any domain knowledge required for cognitive processing
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8
Q

What are production systems in cognitivist cognitive architectures?

A

A production system is a set of rules of the form if-then

  • conditions are propositions on system components
  • production systems are Turing complete and can adapt
  • a production is activated (its action executed) when all of its conditions are satisfied
  • when more than one production rules are satisfied, precedence rules are applied
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9
Q

What are emergent cognitive architectures?

A

Emergent cognitive architectures are frameworks that facilitate development. They model the innate skills of a newborn agent (i.e. its phylogenetic configuration).

  • body is active part of the architecture
  • during ontogeny (development), the architecture is instantiated through the acquisition of experience
  • the architecture needs to provide a structure that accommodates different cognitive functions
  • as a result of development, the architecture can change over time
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10
Q

What are design considerations for cognitive architectures?

A

Scope (compactness and comprehensiveness)
- cognitive architectures are generic and minimalistic -> not desirable to model all relevant cognitive functions

Generality (simplicity and realism)
- generality is an important tradeoff: too general means that the architecture will be under-constrained and meaningless

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11
Q

What are requirements for cognitive architectures?

A

Realism

  • ecological realism: capability of an agent to engage in everyday activities of its natural environment
  • bio-evolutionary realism: model of human intelligence should be reducible to a model of animal intelligence
  • cognitive realism: capture of all essential characteristics of human cognition
  • eclecticism: incorporation of results from prior research

Behavioral characteristics

  • reactivity: quick reactions through immediate and fixed responses without elaborate cognitive processing
  • sequentiality: sequential execution of activities
  • routineness: learning, adaptation and execution of recurring patterns e.g. by trial and error

Cognitive characteristics:

  • explicit processes: accessible and precise
  • implicit processes: inaccessible and imprecise
  • synergistic interaction: implicit & explicit processes interact to complement and supplement each other
  • learning: implicit and explicit processes interact during top-down learning (explicit learning first, implicit learning later) and bottom-up learning (implicit learning first, explicit learning later)
  • modularity: some cognitive faculties are specialized and separated through functional or physical encapsulation

Development

  • value systems and motives: guidance during action selection and motivational drive for development
  • physical embodiment
  • sensorimotor contingencies: store relations between actions and resulting sensory feedback
  • perception: capacity for unsupervised perceptual categorization
  • constitutive autonomy: autonomous operation of developmental processes
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12
Q

What is the requirement of ecological realism?

A

Requirement for cognitive architectures / Realism

capability of an agent to engage in everyday activities of its natural environment

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13
Q

What is the requirement of bio-evolutionary realism?

A

Requirement for cognitive architectures / Realism

the model of human intelligence should be reducible to a model of animal intelligence

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14
Q

What is the requirement of cognitive realism?

A

Requirement for cognitive architectures / Realism

capture of all essential characteristics of human cognition

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15
Q

What is the requirement of eclecticism?

A

Requirement for cognitive architectures / Realism

incorporation of results from prior research

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16
Q

What is the requirement of reactivity?

A

Requirement for cognitive architectures / Behavioral characteristics

quick reactions through immediate and fixed responses without elaborate cognitive processing

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17
Q

What is the requirement of sequentiality?

A

Requirement for cognitive architectures / Behavioral characteristics

sequential execution of activities

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18
Q

What is the requirement of routineness?

A

Requirement for cognitive architectures / Behavioral characteristics

learning, adaptation and execution of recurring patterns e.g. by trial and error

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19
Q

What are explicit and implicit processes?

A

Requirement for cognitive architectures / Cognitive characteristics

  • explicit processes: accessible and precise
  • implicit processes: inaccessible and imprecise
20
Q

What is the requirement of synergistic interaction?

A

Requirement for cognitive architectures / Cognitive characteristics

implicit and explicit processes interact to complement and supplement each other

21
Q

What is top-down and bottom-up learning?

A

Requirement for cognitive architectures / Cognitive characteristics

  • top-down learning: explicit learning first, implicit learning
  • bottom-up learning: implicit learning first, explicit learning later
22
Q

What is the requirement of modularity?

A

Requirement for cognitive architectures / Cognitive characteristics

some cognitive faculties are specialized and separated

23
Q

What is the requirement of physical embodiment?

A

Requirement for cognitive architectures / Development

the body enables actions and to perceive the effects of actions

24
Q

What is the requirement of sensorimotor contigencies?

A

Requirement for cognitive architectures / Development

sensorimotor contingencies store the relations between actions and resulting sensory feedback

25
Q

What is the requirement of perception?

A

Requirement for cognitive architectures / Development

capacity for unsupervised perceptual categorization

26
Q

What is the requirement of constitutive autonomy?

A

Requirement for cognitive architectures / Development

autonomous operation of developmental processes

27
Q

What is ACT-R?

A

Adaptive control of thought – rational is a hybrid cognitive architecture implementing the principles of a unified theory of cognition.

ACT-R is based on modules, buffers, and a production system.

The theory is implemented as a Common Lisp framework.

28
Q

What are ACT-R modules?

A

Modules in ACT-R are independent parallel processing units that encapsulate specific cognitive functions.

Modules are independent from another. Every module can contain arbitrarily complex subfunctions.

Four Main modules:

  • intention module: maintains internal context of intentions for goal-directed behavior; current goal is exposed via the module buffer
  • declarative module: declarative memory
  • visual module: visual perception
  • manual module: implements simple hand model with virtual keyboard/mouse

In addition:
- procedural module: implements the procedural memory system that manages, matches and executes productions. Coordinates interactions between all other modules

29
Q

What are ACT-R buffers?

A

Buffers represent the current state of a module.

Every buffer stores one chunk and is assigned to exactly one module. It is visible to all other modules.

Buffers directly process queries about their content:

  • empty
  • full
  • failure (true iff empty & failure flag is set)
  • requested (true iff chunk in the buffer is the result of a request)
  • unrequested (true iff chunk in the buffer is not the result of a request)
30
Q

What are ACT-R chunks?

A

ACT-R chunks represent declarative knowledge. They are composed of slots, each of which stores a single value (which can also be another chunk).

Example: 8 + 4 = 12

add84

  • addend1 Eight
  • addend2 Four
  • sum Twelve

(diagram: add84 ellipse, Eight/Four/Twelve squares, arrow add84 –sum–> Twelve)

Example: “The black cat with 5 legs sits on the mat”

cat007
…
fact007
…

fact007 –agent—> cat007

31
Q

What is the ACT-R production system?

A

The ACT-R production system coordinates each module through its buffers.

Rules in the production system correspond to procedural knowledge

The production system operates in a critical cycle with a length of 50 ms

  • pattern matching: matching of buffer values with production conditions
  • selection and execution of a matching production
  • results of the production are written back to the corresponding module buffers
32
Q

What are ACT-R productions?

A

Productions are statements about behavior. They can be represented as if-then rules.

Productions are stored in and managed by the procedural module which monitors the state of all module buffers and automatically selects and executes a matching production

Production syntax: every production is identified by a name and is assembled from a list of buffer operations.

(p

==>

)

33
Q

What is the condition of an ACT-R production comprised of?

A

The condition of a production is comprised of a set of buffer tests that are

- patterns which are matched against the current contents of the buffers
=buffername>
    ISA type
    slot1 const1
    slot2 =var1
  • queries for a buffer and module state information
    ?buffername>
    buffer
34
Q

What is the action of a production comprised of?

A 
The action of a production is comprised of a set of
- buffer changes
=buffername>
    ISA type
    slot1 const1
    slot2 =var1
- module requests
\+buffername>
    ISA type
    slot1 const1
    slot2 =var1
35
Q

What is the declarative module and how does it work?

A

The declarative module contains the declarative memory in the form of chunks.

  • requests: search internal memory and return chunk with best match
  • new memories are collected automatically from the buffer when a module is cleared
  • two modes of memory retrieval: purely symbolic matching, time-aware matching

init syntax:
(add-dm
(b ISA …)
)

36
Q

How is a chunk activation calculated?

A

Every chunk i in the declarative memory is assigned an activation Aᵢ:

Aᵢ = Bᵢ + Sᵢ + Pᵢ + 𝜀ᵢ

Bᵢ: base-level activation: recency and use frequency of the chunk

Sᵢ: spreading activation: effect on the contents of the module buffers

Pᵢ: partial matching value: matching-degree of the chunk for the request

𝜀ᵢ: noise value with a transient and permanent component

37
Q

How is the base-level activation calculated?

A

Bᵢ: base-level activation: recency and use frequency of the chunk

Bᵢ = ln (∑ⱼ₌₁ⁿ tⱼ⁻ᵈ) + βᵢ

n: number of presentations of chunk i
tⱼ: time since the j-th presentation
d: decay parameter
βᵢ: constant offset

38
Q

How is the spreading activation calculated?

A

Sᵢ: spreading activation: effect on the contents of the module buffers

Sᵢ = ∑ₖ ∑ⱼ Wₖⱼ Sⱼᵢ

Wₖⱼ: amount of activation from source j in buffer k
Sⱼᵢ: association strength from source j to chunk i

39
Q

How is the partial matching value calculated?

A

Pᵢ: partial matching value: matching-degree of the chunk for the request

Pᵢ= ∑ₖ Pᵢ Mₖᵢ

Pᵢ: match scale parameter that determines the importance of similarity
Mₖᵢ: similarity value between the desired and the actual slot value

40
Q

What is the procedural module and how does it work?

A

The procedural module implements the procedural memory system that manages, matches and executes productions. It coordinates interactions between all other modules.

  • at every time step, the system computes the set of viable production rules by matching the buffer tests against the current buffer contents
  • only one production rule can fire in every time step

Every production has a sub-symbolic utility value Uᵢ

41
Q

How is the sub-symbolic utility value U_i calculated?

A

Every production has a sub-symbolic utility value Uᵢ that can be both set manually or learned online during operation:

Uᵢ = Uᵢ(n−1) + α[Rᵢ(n) − Uᵢ(n−1)]

α: learning rate
Rᵢ(n): reward for production i for its n-th usage

42
Q

What is production compilation?

A

The production compilation mechanism tries to combine productions that fire in sequence.

43
Q

What advantages does ACT-R have in contrast to a normal programming language?

A
  • it advances the understanding of human cognition
  • it is very generic and can be applied to different domains
  • deep explanations of cognitive processing go beyond the task level
44
Q

What are the two types of knowledge and their corresponding representation in ACT-R?

A
  • declarative knowledge - represented by chunks

- procedural knowledge - rules of the production system

45
Q

What is the difference between implicit and explicit learning?

A

When the process used to gain information is known, it is called explicit learning. It differs from implicit learning because of the awareness factor.

46
Q

ACT-R model for counting

A

Task: Count from num1 to num2

Chunk Types
(chunk-type count-order first second)
(chunk-type count-from start end count)
Initialize Declarative Memory
(add-dm
    (b ISA count-order first 1 second 2)
    (c ISA count-order first 2 second 3)
    (d ISA count-order first 3 second 4)
    (e ISA count-order first 4 second 5)
    (f ISA count-order first 5 second 6)
    (first-goal ISA count-from start 2 end 4)
)

Set the Initial Goal
(goal-focus first-goal)

Define the Start Production
(p start
  =goal>
    ISA count-from
    start =num1
    count nil
==>
  =goal>
    ISA count-from
    count =num1
  \+retrieval>
    ISA count-order
    first =num1
)
Define the Increment Production
(p increment
  =goal>
    ISA count-from
    count =num1
    - end =num1
  =retrieval>
    ISA count-order
    first =num1
    second =num2
==>
  =goal>
    ISA count-from
    count =num2
  \+retrieval>
    ISA count-order
    first =num2
)
The Stop Production
(p stop
  =goal>
    ISA count-from
    count =num
    end =num
==>
  -goal>
)

Cognitive Systems (7 decks)

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