Experiment 1
Miller (56)
Capacity of STM
2-3 lessons + Home Study
Cognitive – Unit 1
Purpose of experiments
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To understand the purpose of Ψ
To recognise the difficulty in getting exact data
To criticise experimental design
To design, or vary designs, yourself
To work through A-P-F-C in practice
To remember key core studies in special depth
We will do few experiments, but in detail. You need
to understand other studies through this lens.
Instructions
• Have a pen always in hand.
• Have a piece of paper numbered 1 - 8 down one
side and 9-16 down the middle. Space the rows.
• You will be shown a series of slides with
sequences of letters and / or numbers. The
duration of each slide will be VERY SHORT.
• You cannot write while a slide is up. Once the
screen turns white, write the sequence QUICKLY,
then look straight back up again. Do not be neat.
• Do not attempt to “go back” – it’s too fast.
Ready…
BQ7
9GM
JP1S
Y6WC
P3B9A
681HK
L9FN8
U4DW2
7QNRT3
T8JZ9F
8MF4ELH
NFX8K3P
UC8E3J1L
S9K4GV2R
HG8WK1CLA
YVW8N9D4S
You have finished.
Relax.
DON’T SCORE IT YET
Discuss your impressions of what it felt like.
Make good detailed notes of how it felt for
you and others –
A good experimenter MUST EXPERIENCE THE
EXPERIMENT as it affects participants, in order
to understand issues in the design.
Check your answers & report
1.
2.
3.
4.
5.
6.
7.
8.
BQ7
9GM
JP1S
Y6WC
P39BA
681HK
LFN8
U4DW2
9. 7QNRT3
10. T8JZ9F
11. 8MF4ELH
12. NFX8K3P
13. UC8E3J1L
14. S9K4GV2R
15. HG8WK1CLA
16. YW8N9D4S
How many did you score? Are there any problems scoring?
Reflect
• What is the study testing?
• What effects did the procedures impose on the
participants? Why? Did they work as intended?
• What variations are there between individuals?
• What trends are emerging in results?
• How would you represent the data?
What conclusion can you draw from these
findings?
Miller (1956), after Jacobs (1887)
• “The Magical Number 7, +/- 2”
• Tested by digit span technique
• Capacity of STM is 5-9 items, varying by
individual
• Constrained to focus on STM
• Important not to allow meaning to occur:
“U A E 2 0 1 1 D B S”
“1914191819391945” (“chunking”)
Now…
Do it again.
Exactly the same. All over again.
Get your clean sheet of paper ready.
Instructions
• Have a pen always in hand.
• Have a piece of paper numbered 1 - 8 down one
side and 9-16 down the middle. Space the rows.
• You will be shown a series of slides with
sequences of letters and / or numbers. The
duration of each slide will be VERY SHORT.
• You cannot write while a slide is up. Once the
screen turns white, write the sequence QUICKLY,
then look straight back up again. Do not be neat.
• Do not attempt to “go back” – it’s too fast.
Ready…
BQ7
9GM
JP1S
Y6WC
P3B9A
681HK
L9FN8
U4DW2
7QNRT3
T8JZ9F
8MF4ELH
NFX8K3P
UC8E3J1L
S9K4GV2R
HG8WK1CLA
YVW8N9D4S
You have finished.
Relax.
DON’T SCORE IT YET
Discuss your impressions of what it felt like to
repeat the experiment. Make good detailed
notes of how it felt for you and others –
A good experimenter must understand the
effects of the experiment in detail.
Check your answers & report
1.
2.
3.
4.
5.
6.
7.
8.
BQ7
9GM
JP1S
Y6WC
P39BA
681HK
LFN8
U4DW2
9. 7QNRT3
10. T8JZ9F
11. 8MF4ELH
12. NFX8K3P
13. UC8E3J1L
14. S9K4GV2R
15. HG8WK1CLA
16. YW8N9D4S
How many did you score? More or less than last time?
Problems scoring? Repeated mistakes?
Conclusions from repeat?
Work in groups of 4-6.
Look at both individuals and the group’s data.
Discuss what has changed in the data, and
share this with the class after summarising.
Criticisms
This is one of the SIMPLEST experiments you can
imagine in Ψ. And yet…
Can you think of potential issues that might
invalidate the data we have?
These are called METHODOLOGICAL PROBLEMS.
See how your list compares to the next slide.
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Is the timing fair? Hard at the end?
How to count data from “Give-up-ers”?
What if someone cheated / didn’t understand instructions?
Fatigue effect? Despair effect?
What if wrong on 6, but right on 7? How to score?
Effect on poor writers? Would aural change the effect?
Font size? It shrunk at the end!
Font choice makes letters similar?
Meaning for some ppts but not others? Allows chunking of
items…
• Aurally-awkward (“NFX8”) blocks?
• White screen allows repetition-for-memory? (Why no
“distractor” task?)
Order these, in your opinion, in likely effect. Define.
Debriefing
Debriefing is NOT removing someone’s underwear.
In effect, by having the study explained to you, you’ve
been debriefed. Ppts who have not been debriefed can
• suffer anxiety
• feel inadequate
• mistrust scientific research
• sue you
ALWAYS DEBRIEF – EXPLAIN THE EXPERIMENT
AFTERWARDS. And invite them to see the results.
Replication
Findings are only any acceptable if REPLICABLE.
You need to work in pairs and replicate the
experiment we have conducted.
Design it slightly differently to this one. How?
How much data do you need?
How will you acquire participants?
Will the choice of participants affect the outcome?
Is your design ethically sound?
Conduct and report
First, get your design AUTHORISED. Provide written
AP, with table of M and E problems and how they
will be avoided. (Share openly.)
Get permissions as necessary within school. (Pair.)
Run the experiment. (Pair.)
Write the APFC report in full detail. (Solo.)
Extension options
1. Replicate your own study under identical
conditions to explore natural variability.
2. Increase study size to establish more valid
results. How do you know how many you need?
3. Change participant qualities (age, ability, gender,
status etc.)
4. Change conditions (time of day, noise, screen
type / distance etc.)
5. Change design (aural / visual, ppt numbers,
timings, distractor tasks etc.)