Experiment 1Miller (56)

Capacity of STM2-3 lessons + Home Study

Cognitive – Unit 1

Purpose of experiments

• 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…

B Q 7

9 G M

J P 1 S

Y 6 W C

P 3 B 9 A

6 8 1 H K

L 9 F N 8

U 4 D W 2

7 Q N R T 3

T 8 J Z 9 F

8 M F 4 E L H

N F X 8 K 3 P

U C 8 E 3 J 1 L

S 9 K 4 G V 2 R

H G 8 W K 1 C L A

Y V W 8 N 9 D 4 S

You have finished.

Relax.

DON’T SCORE IT YETDiscuss 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 & report1. BQ72. 9GM3. JP1S4. Y6WC5. P39BA6. 681HK7. LFN88. U4DW2

9. 7QNRT310. T8JZ9F11. 8MF4ELH12. NFX8K3P13. UC8E3J1L14. S9K4GV2R15. HG8WK1CLA16. 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…

B Q 7

9 G M

J P 1 S

Y 6 W C

P 3 B 9 A

6 8 1 H K

L 9 F N 8

U 4 D W 2

7 Q N R T 3

T 8 J Z 9 F

8 M F 4 E L H

N F X 8 K 3 P

U C 8 E 3 J 1 L

S 9 K 4 G V 2 R

H G 8 W K 1 C L A

Y V W 8 N 9 D 4 S

You have finished.

Relax.

DON’T SCORE IT YETDiscuss 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 & report1. BQ72. 9GM3. JP1S4. Y6WC5. P39BA6. 681HK7. LFN88. U4DW2

9. 7QNRT310. T8JZ9F11. 8MF4ELH12. NFX8K3P13. UC8E3J1L14. S9K4GV2R15. HG8WK1CLA16. 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.

• 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.

DebriefingDebriefing 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.)