Lecture 3 - Marr's Levels of Analysis

Question 1

theoretical constructs

Answer 1

perception, recognition

Question 2

operational definition

Answer 2

to help measure when theoretical constructs are present: “indicates stuff going on in there”

something the scientist comes up with: “when you witness this thing, you can feel confident that this theoretical construct was present”

Question 3

Marr’s Levels of Analysis

Answer 3

three different perspectives of the same issue

these levels interact

study of one can inform our approach to another

Question 4

Computational Level

Answer 4

most abstract

what is it doing when faced with an input, how does it behave?

inputs coming in and outputs going out of the “black box”

Question 5

Algorithmic level

pt. 1

Answer 5

what steps does the system take to try and accomplish that goal or solve that problem

parse it up: “what’s it trying to do,, it does A, B, C, D… to try to solve this problem characterized at the computational level

Question 6

Implementation Level

Answer 6

the most concrete: nuts and bolts

“ok, how is the system actually accomplishing it? what are the neurons doing? firing pattern? computer wired together?”

have to know what system you’re dealing with

Question 7

How to decide which level it is

Answer 7

Focus on: What was the explanation? What was the answer given by the experimenter? What were they explaining or describing to you?

Question 8

Algorithm Example

Answer 8

make some steps or some model that an experiment is working on

Question 9

How to determine the nature of inputs and outputs considered at computational level?

Answer 9

the type of problem being solved by the system (“black box”)

what was the system doing? how was it responding when the input came in? what was the behavior?

Question 10

which element in model is best matched to the ‘input’ stage of Marr’s computational level?

Answer 10

distal stimulus: the input in isolation of anything else, environmental stimulus that is giving you an input into the system and there’s an output coming out

input common to everyone: you would want to present the same distal stimulus to everyone in an experiment

Question 11

proximal stimulus

Answer 11

the input as its hitting the sensory organ

has some property of the receiver, so the input coming in is changing at the level of the proximal stimulus (ppl have different vision capabilities)

Question 12

Algorithmic Level

pt. 2

Answer 12

what steps or procedure going on in the “black box”

“to get from that input to that output the system went through the following steps…”

we still don’t know what kind of system (human brain, computer, alien, etc) is working on the problem

We only specify the steps the system takes and what kinds of info (representations) it manipulates

Question 13

Real-World Algorithmic example would look like…

Answer 13

some kind of model or equation, when it specifies a numerical, regular relationship

Question 14

Implementation Level

and the black box

Answer 14

get to look into the “black box” and see what kind of system you’re working with and how those components are interacting to embody that algorithm or produce that output

Question 15

Implementation Level

Input –> …….. –>

Answer 15

Neural Activity

Question 16

Example of Implementation Level processes

Answer 16

receptors fire, signals go to complex cells, etc.

we can specify how the elements of the system work together

Question 17

the level at which you begin your analysis can determine the types of….and… you will use

Answer 17

tools and methods

Question 18

Computational level introduces what kinds of explanations?

Answer 18

behavioral explanations: a behavioral output given some input

“when the thing sees this the thing does that”

Question 19

Algorithmic level introduces what kinds of explanations?

Answer 19

characterize a model, a psychological theory, a psychophysical law ——-

something that tells you regularities such that if you plug inputs into those regularities you will know what the output will be - tells you the steps being taken

Question 20

Implementation level explanations

Answer 20

some explanation about the physiology: “here’s what the cells in this area are doing”