Last Class we ended with
How to investigate Perception & Cognition

Ask your subjects (Introspectionism)

Look at S-R patterns (Behaviorism)

Infer mental processes (Cognitive Psychology)
– from S-R patterns (Reaction Time, Accuracy)
– from neural patterns (cognitive neuroscience)
Cognitive Psychology
Response
Stimulus
Information Processing
Representations
Study stimulus-response relations to infer the underlying
mental processes. The contents of the mind CAN be studied
scientifically. How?
Three models: The ‘black box’, the ‘jukebox’, the ‘mind box’
The black box
Stimulus
(input)
Response
(output)
1. Observe the Input/output relation
2 create a ‘model’ (abstract representation) to account for the I/O
- requires a little bit of background knowledge
(e.g., naïve physics, naïve biology),
- It is a ‘functional’ model (how the box functions)
The black box: A ‘model’
Pull
Force (push)
Stimulus
(input)
A
Response
(output)
- Is ‘A’ stick connected to the brown stick?
- Can we run an experiment to find out?
-vary input & measure output, from that I/O pattern make:
- inferences about the internal constructs (i.e. create a functional
model)
The jukebox
Input (selection)
ABCDEFGHIJKLMN
Output
(a particular song)
As with the ‘black box’, we need to infer how it works (a
functional model). We do this from the I/O pattern, and a little
bit of background knowledge. ANY GUESSES?
Stack
of disks
A
B.
.
.
.
.
.
selector
Turntable
How can we test this model?
- Assume that selector always starts from top
- Measure how long it takes to start playing
Graph data
Functional Model of the ‘jukebox’
Move selector
arm to top
of stack
Move selector
to next
record
Is record
selected one?
yes
Put record
on
turntable
no
Stack
of disks
A
B.
.
.
.
.
.
selector
-A hardware
- A ‘functional’ architecture
(this is what Cog Psy studies)
The mind box


The same approach to study the functional architecture of
the jukebox, can be applied to the study of the functional
architecture of the mind.
Create an internal model by looking at the I/O pattern
– Input (independent variable)
– Output (dependent variable): usually Reaction Time (RT)

Example: Sternberg search (web).
–
–
–
–
A set of letters will appear briefly on the screen for you to study
The letters will disappear
3 seconds later one probe item will appear.
Your task is to decide whether the probe item was in the initial list.
Say ‘yes’ if the probe was in the list, ‘no’ if it wasn’t. READY?
Memory set (t1)
P Z T A C H
- Set size can vary
delay
Probe (t2):
-Present in set, or
-Absent in set
H
Memory system
X T N B D
Y
Create an
input
representation
Retrieve a
representation
from memory
Y
X
Compare
the two
representations
Y
X
no match
Sequential Model: Predictions
- Larger memory set  slower RT
-‘yes’ trials  faster RT
-‘yes’ trials  shallower slope
match
respond
“yes”
last
yes
respond
memory
“no”
rep?
no
Memory system
X T N B D
Y
Create an
input
representation
Y
Compare to all
representations
simultaneously
Y
match
respond
“yes”
Parallel Model: Predictions
- Larger memory set  same RT
-‘yes’ trials  same RT
-But caveats exist!
no match
respond
“no”
Contrasting the two models

I.V.s (& levels):
– ??
– ??

D.V.:?
X T
B
N B D
N
X T N
B
D
T
Sternberg (1967)