PSY2002 W4 Models (L)

Question 1

What is a model?

Answer 1

simplified (or idealized) representation of a more complex thing

Question 2

What is the Marr’s three levels of analysis?

Answer 2

1. Computation – the problem being solved
2. Algorithm – the steps/rules to solve it
3. Implementation – the actual machinery

Question 3

What is abstraction?

Answer 3

generating general rules and concepts from specific information

Question 4

What is simplification ?

Answer 4

making something simpler

Question 5

What is algorithm (rules)?

Answer 5

Rules: What representations and algorithms can we generate, given specific neural circuits?

Question 6

What is top-down appraoch?

Answer 6

Problem: What is the problem we’re trying to solve
Rules: What representations and algorithms can solve this problem?
Implementation: How can these representations and algorithms be implemented in neural circuits?

Question 7

What is bottom-up appraoch?

Answer 7

Implementation: the machinery of neural circuits
Rules: What representations and algorithms can we generate, given specific neural circuits?
Problem: What problems are solved by these algorithms?
Marr (1982): “…an algorithm is likely to be understood more readily by understanding the nature of the problem being solved than by examining the mechanism (and the hardware) in which it is embodied.“

Question 8

What are Statistical models?

Answer 8

a mathematical relationship between variables, that hold under specific assumptions

Question 9

What are Theoritical models?

Answer 9

(in cognition) a description of the relationship between different mental processes, that makes assumptions about the nature of these processes

Question 10

What is behaviourism?

Answer 10

Input > Mind [black box (you can’t understand] > Output (behaviour)
Behaviourists want to understand what is going on in the mind by changing the inputs and observing the outputs.

Question 11

What is Cognitive “box-and-arrow” models?

Answer 11

Box-and-arrow can be called informal cognitive models.

Models that describe the relationship between different mental processes, under the assumption that the mind operates like multi-staged information-processing machines. Box and arrow models started off simple, but can gradually become quite complex.

Question 12

What are Formal Cognitive Models?

Answer 12

mathematical description of the relationship between mental processes. Usually expressed through computer code

Question 13

Models are characteristed by what?

Answer 13

All models simplify and make things more abstract.
Simplification and Abstraction
When we create a model, we acknowledge that we’re not going to describe all the information we’re describing, only the parts we think are critical for what we’re trying to represent.

Question 14

What is the right level of abstraction of a model?

Answer 14

depends on the question we are asking and/or what we’re trying to convey.
“All models are wrong, but some are useful. “- George Box (1976)
“The map is not the territory. “- Alfred Korzybski (1931)

Question 15

What do models in science must produce?

Answer 15

Predictions.
These predictions can be directional or numerical. Models that provides numerical predictions can be more or less accurate.
Karl Popper - Non-scientific theories explain after the fact but cannot provide falsifiable predictions

Question 16

What are specific numerical prediction?

Answer 16

They do not give explanations but it steams from a theory (explanation) - theoretical model
Difference between statistic model and theoretical model (trying to explain, with a theory behind it)

Question 17

How do we use models to predict and explain?

Answer 17

Framework <> theory <> model <> hypothesis <> data

Question 18

What is framework?

Models to predict and explain

Answer 18

The conceptual system that defines terms and provide context

Cognitive psychology

Question 19

What is a theory?

Models to predict and explain

Answer 19

A scientific proposition that provides relations between phenomena

Early-Selection theory

A schematic representation of a theory, more limited in its scope

Broadbent’s Filter model

Question 20

What is a hypothesis?

Models to predict and explain

Answer 20

A narrow testable statement

Irrelevant stimuli that contain target-defining feature will be automatically detected

Question 21

What is data?

Models to predict and explain

Answer 21

Collected observation, often as part of an experiment

New “gorilla’ experiment, detection rates, t-tests.

Question 22

What is model ?

Model to explain and predict

Answer 22

A schematic representation of a theory, more limited in its scope

Broadbent’s Filter model

Question 23

What are explanation without exact prediction?

Answer 23

Models of schizophrenia can indicate causes but cannot (yet?) predict individual cases.
The model be able to predict group differences, but not individual cases.

Question 24

What is prediction without explanation?

Answer 24

Some models can predict whether an individual will develop Alzheimer, even though we still aren’t close to understand the factors that explain Alzheimer

Question 25

What are informal cognitive models?

Answer 25

a verbal description of the relationship between different cognitive procedure:
Where often some assumptions are implicit.
Often provides only directional predictions

Question 26

What are formal/computational models?

Answer 26

Formal/computational models: a mathematical description of the relationship between different cognitive procedure, often instantiated via computer program/simulation:
Assumptions are explicit.
Often provides numerical predictions

Question 27

How do formal models explain?

Answer 27

Specification – a formal description of the relations described by a theory - The formal model, comprised of symbolic representations

Implementation – a specific instantiation of a specification – a computer program ale to simulate and predict numerical outputs from input.

Question 28

Why are formal models more specific in prediction?

Gottfried Wihelm Leibniz, 1685

Answer 28

“Let us calculate, without further ado, and see who is right”

By having a numerical simulation, we can see if the model provides unreasonable predictions (easier to reject bad models). Can help us select which experiments to perform.
By having numerical predictions, we can provide a more subtle form of hypothesis testing. We can see how close a model is to predicting an actual result.

Question 29

Why do formal models have more counter-intuitive prediction?

Answer 29

A model can more clearly describe which predictions follow from a model.
With informal models, it’s hard to notice when they make counter-intuitive predictions. Formal models clearly produce such predictions.

Question 30

Why do formal models benefit of explicit assumptions?

Answer 30

By making assumptions explicit, we can reveal unanswered questions, flaws in our reasoning, contradictory or unreasonable assumptions. Feynman’s blackboard (“what I cannot create, I do not understand”)

Question 31

How does David Marr’s Levels of analysis understand the brain?

Answer 31

Problem: We can only ever hope to sample from a tiny fraction of its activity, in a tiny fraction of a bit of brain
The way to make sense of brain data was to break any brain problem into three levels:

1. Computation – the problem being solved
2. Algorithm – the steps/rules to solve it
3. Implementation – the actual machinery