Lesson Three: Encoding, Capacity, and DurationSpecification

A – Models of Memory

1. The multi-store model including concepts of encoding, capacity and duration. Strength and weaknesses of the model

2. The working memory model including its strengths and weaknesses

B – Memory in everyday life

1. Eyewitness testimony and factors affecting the accuracy of EWT including anxiety and age of witness

2. Misleading information and the use of cognitive interview

3. Strategies for memory improvement

Homework

Bring in a photograph from your childhood (if you do not have one bring in an

item from your childhood)

Draw a diagram to demonstrate the function of the Multi-Store Model of

Memory (6 marks)

Starter

Think of an example of each type of memory:

Iconic, Echoic, and Haptic

Lesson Objectives:

By the end of this lesson, you will be able to:• Apply the concepts of capacity and duration to

memory stores• Understand the factors affecting capacity and

duration and describe how they have been measured

Key Words to know by the end of the lesson:

• Capacity• Duration• Digit span technique• Serial recall• Rehearsal• Chunking • Trigrams

Link to last lesson

Can you describe the evidence for a distinction between STM and LTM?

A case study was carried out on Peter whose brain was damaged in a motorcycle accident. Psychologists tested how many numbers he could hold in his short-term memory. They did this by reading him lists of numbers and asking him to recall the numbers immediately in the right order. He could recall a maximum of two items. The psychologists found that his long-

term memory was normal.

Eye on the exam

• C) Identify one ethical issue associated with this case study of Peter. Suggest how psychologists could deal with this ethical issue. (4 marks)

– Ethical issue

– How psychologists could deal with this ethical issue

Multistore ModelMultistore ModelInformation is registered through the sensory & attentional systems

STM

A limited amount of info is held for a short time in STM

The rehearsal loop allows info to be maintained in STM for longer periods

LTM

Rehearsal allows info to be moved to LTM for long term storage

Capacity in LTM Capacity in LTM • LTM has an LTM has an unlimited capacity unlimited capacity

(as far as we know)(as far as we know)

• Your LTM can never be full!!!Your LTM can never be full!!!

Capacity in STM Capacity in STM • Do the following mental arithmetic…

*4 + 7= * 11 + 35= *6 + 3 + 4 – 2 x 30 =• The problems that you may have had with the last one

demonstrate the limited capacity of STM• As you try to work out the subsequent parts of the equation, you

have to lose information to make room for new items• The size of the capacity of STM depends on how we measure it

Key Terms Explained:

• Digit Span Technique: a way of measuring capacity in STM. Participants have to repeat back strings of digits (that increase in size) until they can no longer repeat the sequence of digits correctly

• Serial Recall: a way of testing STM where participants are required to recall items in the correct order of presentation

Try This!

• This is an example of a serial recall task…This is an example of a serial recall task…

• How far can you get before you start to How far can you get before you start to forget the order of presentation?forget the order of presentation?

• George Miller (1956) – George Miller (1956) – ‘The Magical ‘The Magical Number Seven, Plus or Minus Two’Number Seven, Plus or Minus Two’

• We can hold about 7 ‘items’ in out STM We can hold about 7 ‘items’ in out STM with a range between 5 – 9.with a range between 5 – 9.

Items?

ITEMS?

What do we mean by items?!What do we mean by items?!

• Miller Miller

• The capacity of STM: determined by the The capacity of STM: determined by the number of ‘number of ‘chunks’chunks’ (7, + or – 2 chunks) (7, + or – 2 chunks) rather than the number of individual letters rather than the number of individual letters or numbers. or numbers.

• Try and remember the numbers on the Try and remember the numbers on the following page in the correct order…following page in the correct order…

• 999999

• 911911

• 5432154321

• 118118118118

• 2200222002

• 3425034250

• 61681336168133

• 0035374972168000353749721680

• 1417711350440014177113504400

How did you do?How did you do?

• See how meaningful pieces of information See how meaningful pieces of information can stay in your STM longer than others?can stay in your STM longer than others?

• You have You have rehearsedrehearsed these before and in these before and in this way your LTM helps your STMthis way your LTM helps your STM

• Miller

• Semantic (meaningful chunks) which are recognisable, make recall easier.

• So memory span can be increased by chunking!

• Too vague? – how much information can me contained in a chunk?

• Simon (1974)• Immediate serial recall of one-syllable, two-syllable,

three-syllable words & two word and eight word phrases.

• He found that the span in chunks was less with eight word phrases than with smaller chunks.

• So the capacity depends on the nature of the material to be remembered.

• Unlike a There is no way of defining a basic unit of information to be stored in human STM.

Factor affecting capacity

• Rhythmic grouping

Question…Question…

• What could What could affectaffect the capacity of STM? the capacity of STM?

– Influence of LTM: (Cowan, 2000)Influence of LTM: (Cowan, 2000)– Reading Aloud (Baddeley, 1999)Reading Aloud (Baddeley, 1999)– Pronunciation time (Hitch et al, 1984)Pronunciation time (Hitch et al, 1984)– Individual differences (McLeod and Donnelly, 1993)Individual differences (McLeod and Donnelly, 1993)

– Using p12 in your textbook and the Baddeley et al. Using p12 in your textbook and the Baddeley et al. (1975) study in you course pack write down (on the (1975) study in you course pack write down (on the same page as this study) how the above factors affect same page as this study) how the above factors affect capacity. capacity.

DurationDuration in STM in STM

Let’s try Peterson and Peterson’s (1959) experiment….

AIM: To find out how long items would remain in STM without rehearsal.

PROCEDURE: They presented participants with a consonant Trigram Trigram ((3 consecutive letters that do not form a pronounceable unit, e.g. CKM, FNW)…..

BPN

TPB

TGK

QTK

Peterson & Peterson…..

• FINDINGS: This procedure was repeated several times (trials) using different trigrams on each presentation.

• Ps were able to recall:• 80% correctly after 3 second interval

• Fewer than 10% correctly after 18 second interval

• CONCLUSION: information disappears or decays very rapidly from STM when rehearsal is prevented

Methodological issues…Methodological issues…

• Read through the Peterson & Peterson study in Read through the Peterson & Peterson study in your course pack - what do you think may be your course pack - what do you think may be potential methodological issues?potential methodological issues?

• Ecological validity (artificiality of trigrams?)Ecological validity (artificiality of trigrams?)• Capacity or Duration? (displacement – Capacity or Duration? (displacement –

remember the mental arithmetic?)remember the mental arithmetic?)• They might have mixed up the trigrams with They might have mixed up the trigrams with

those experienced in earlier trials (proactive those experienced in earlier trials (proactive interference)interference)

Factors that affect the duration in STM

• Rehearsal• Intention to recall (Sebrechts et al., et al

1989) • Amount of information to be recalled

(Murdock, 1961)

• Underneath Peterson & Peterson study explain how the above factors can affect duration.

Duration in LTM

Answer the following questions ..…

1. Write down (in as much detail as possible) your first memory

2. What factors could affect our ability to keep memories long-term?

• Bahrick et al. (1975)

• AIM:

• PARTICIPANTS:

• PROCEDURE:

• Read through study in course pack.

Duration in LTM

Factors affecting duration in LTM p 14-15

• Experimental techniques

• Depth of learning (Bahrick & Hall, 1991)

• Pattern of learning

• Nature of material to be learned (Conway et al., 1991)

• Briefly explain these factors at the bottom of the study sheet.

Check your key words:

• Capacity• Duration• Digit span technique• Serial recall• Rehearsal• Chunking • Trigrams

Plenary - Eye on the exam

• Using the list below, complete the table to distinguish between long-term memory and short term memory. (3 marks)

• Unlimited

• Up to a lifetime

• 7 +/-/2 items

• Mainly acoustic

• Seconds

• Mainly semantic

Short-term memory (STM) Long-term memory (LTM)

Capacity

Duration

Encoding

Plenary - Eye on the examPlenary - Eye on the examOutline the key features of the multi-store model Outline the key features of the multi-store model of memory. (6marks)of memory. (6marks)

• This straightforward question that asks you to demonstrate your This straightforward question that asks you to demonstrate your knowledge about the multi-store model. Remember, this question knowledge about the multi-store model. Remember, this question requires AO1 skills and you are expected therefore to demonstrate requires AO1 skills and you are expected therefore to demonstrate your knowledge and understanding. You are not required to provide your knowledge and understanding. You are not required to provide any analysis or evaluation of this model.any analysis or evaluation of this model.

• You must also remember that a model is an explanation or theory. It You must also remember that a model is an explanation or theory. It is not a study.is not a study.

• Take care to provide a balanced answer. If for example you spend Take care to provide a balanced answer. If for example you spend too much time describing (rather than briefly outlining) the memory too much time describing (rather than briefly outlining) the memory stores, you will not have enough time to do justice to the other stores, you will not have enough time to do justice to the other aspects of the model.aspects of the model.

Your answer should include an Your answer should include an short account of: short account of:

• The three separate stores (sensory, short-term and long-The three separate stores (sensory, short-term and long-term) and their main characteristics in terms of encoding, term) and their main characteristics in terms of encoding, capacity and duration. capacity and duration.

• The processes used to transfer information from one The processes used to transfer information from one store to another (attention to pass information on from store to another (attention to pass information on from the sensory store and rehearsal to pass information from the sensory store and rehearsal to pass information from the STM to LTM). Recoding may also be needed the STM to LTM). Recoding may also be needed between one store and the next.between one store and the next.

• Why information may be lost from each store (through Why information may be lost from each store (through decay from sensory, through decay and displacement decay from sensory, through decay and displacement from STM and through interference and retrieval failure from STM and through interference and retrieval failure from LTM).from LTM).

Homework

Bring in a photograph from your childhood (if you do not Bring in a photograph from your childhood (if you do not have one bring in an item from your childhood)have one bring in an item from your childhood)

•Draw a diagram to demonstrate the function of the Multi-Store Model of Memory (6 marks).

This will provide a useful revision tool for you on the MSM but remember it’s the detail that’s marked so don’t spend too long making it pretty ……