Memory L1 - Coding, Capacity & Duration Of STM & LTM

Question 1

Short term memory definition

Answer 1

• Short-term memory stores and allows recall of information for a period of several seconds up to 30 seconds without rehearsal
• Its capacity is very limited

Question 2

Long term memory definition

Answer 2

• Stores and enables us to recall of information from the more distant past
• Its capacity is unlimited and duration is potentially a lifetime

Question 3

3 ways short and long term memory are different

Answer 3

• duration
• capacity
• coding

Question 4

Duration definition

Answer 4

A measure of how long information can be stored for or how long it lasts

Question 5

Short term memory duration

Answer 5

• Short-term memories do not last long
• In order to keep information in our STM for more than a few seconds, we will most commonly rehearse it (repeat it over and over again, either aloud or in our heads) to keep it active

Question 6

Short term memory duration study

Answer 6

Peterson and Peterson (1959)

Question 7

Peterson and Peterson (1959)

Answer 7

Method
- Participants (24 undergraduate students) were presented with a consonant trigram (3 random consonants) e.g. ZFB, They were then asked to count backwards in threes to stop them repeating/rehearsing the consonant trigram.
- After intervals of either 3, 6, 9, 12, 15 or 18 seconds, participants had to stop counting and repeat the trigram - This was repeated using different trigrams
Results
Participants could remember about 90% of trigrams after 3 seconds, 20% after 9 seconds, and less than 10% when there was 18 second interval
conclusion
Information decays (disappears) very quickly when you can’t rehearse it. The maximum STM duration is about 18 seconds.

Question 8

Peterson and Peterson evaluation

Answer 8

strengths
Controlled variables
weaknesses
Unrealistic
Confusion

Question 9

Controlled variables - Peterson and Peterson

Answer 9

• A strength of Peterson and Peterson’s study is that it is a lab experiment where variables can be tightly controlled for example, how many trigrams and for how long they are presented
• The procedure can also be replicated to test if results are reliable – for example the nonsense trigrams can be repeated on lots of participants over time and the duration of STM can be tested to see if it has changed over time (i.e. gone better or worse).

Question 10

Peterson and Peterson - unrealistic

Answer 10

• However trigrams are unrealistic things to remember. How often in life do we have to remember meaningless consonant trigrams?
• It can therefore be said the experiment has low ecological validity (the findings may not apply to everyday life)
• unconsciously try to remember them

Question 11

Peterson & Peterson - causes confusion

Answer 11

• Also, the trigrams presented on earlier trials may have caused confusion or interference when participants came to remember trigrams in later trials so we are not sure whether the results gained from the participants were due to them forgetting the trigrams or being confused due to interference– this then may question how the duration of STM was tested.

Question 12

Overall STM duration conclusion

Answer 12

• Since Peterson and Peterson’s study more research into the STM duration has been carried out
• overall conclusion is that the STM maximum duration is between 18-30 seconds without rehearsal.

Question 13

LTM duration study

Answer 13

Bahrick et al. (1975)

Question 14

Bahrick et al. (1975)

Answer 14

method
- They tested how well 400 American participants (aged between 17-74 years) could remember their former classmates by asking them to identify pictures, matching names to pictures and recalling names with no picture cue.
results
- Even after 48 years, when asked to link names and faces, accuracy was at about 70%.
- However, when pps were asked to free recall the names of their classmates, then accuracy after 48 years was 30%.
conclusion
- 30-50 years on, participants were still able to remember their classmates - backs up the idea that long term memories can last a lifetime
- The study also showed that individuals cannot immediately access all the information stored in their LTM- as was shown in the free recall task, however when cues (in this case photographs) are presented, then recall is much higher suggesting that cues are often needed to help retrieval.

Question 15

Bahrick et al (1975) evaluation

Answer 15

strengths
External validity
weaknesses
Natural experiment
Specific information

Question 16

Bahrick et al (1975) - external validity

Answer 16

• Bahrick’s experiment has high external validity – can be applied outside of the study - this is because the researchers investigated meaningful material (e.g. remembering class mates)
• therefore this study has higher ecological validity than Peterson’s study which uses nonsense trigrams which are meaningless in the everyday world but remembering names is an everyday task so Bahrick’s study is relevant to everyday life.
• Furthermore this study allows us to give a better estimate of the duration of LTM due to the meaningful material used to test it.

Question 17

Bahrick et al (1975) - natural experiment

Answer 17

• Because Bahrick’s study it is a natural experiment, the experimenter had less control of the IV thus it’s likely that some of the names had since been rehearsed e.g. if classmates were still in touch or had been talked about since
• This would be a confounding variable, making results potentially invalid

Question 18

Bahrick et al (1975) - specific information

Answer 18

• It only looked at a very specific type of information- names of classmates
• This type of information is particularly meaningful and regularly rehearsed
• Obviously not all LTMs remain there for a lifetime

Question 19

Capacity of memory definition

Answer 19

This is a measure of the format in which information is stored in the various memory stores, in other words, how much information can be held or stored.

Question 20

LTM & STM capacity

Answer 20

• LTM has a potentially unlimited capacity
• whilst STM has a very limited capacity.

Question 21

STM capacity studies

Answer 21

Jacobs (1887)
Miller (1956)

Question 22

Jacobs (1887)

Answer 22

method
- developed the serial digit span technique - researcher read out 4 digits and the participant was asked to repeat it back immediately.
- More digits was then added until the participant could not repeat back the digit string accurately
results
- On average about 9 digits and 7 letters were correctly recalled
- This capacity increased with age during childhood (average digit span for 8 year olds was only 6)
- This may because there is a gradual increase in brain capacity and /or because people develop strategies to improve their digit span, such as chunking
- Digits may have been easier to recall as there are only 10 digits to remember, compared to 26 letters.

Question 23

Jacobs (1887) evaluation

Answer 23

strengths
Repeated study
Weaknesses
Ecological validity
Confusion
Long time ago

Question 24

Jacobs (1887) - repeated study

Answer 24

The study has been repeated various times suggesting that it’s a valid and reliable study

Question 25

Jacobs (1887) - ecological validity

Answer 25

• One problem with Jacob’s research is that it lacks ecological validity- learning random lists of numbers and repeating them back is not a realistic method to test the capacity of STM
• More meaningful information may be recalled better, perhaps showing STM to have an even greater capacity.

Question 26

Jacobs (1887) - confusion

Answer 26

• Also, another problem with Jacob’s study is the fact that it could be that previous sequences recalled by participants may have confused them on later trials so we don’t know if that factor became a confounding variable which affected how the capacity of the STM was measured.

Question 27

Jacobs (1887) - long time ago

Answer 27

• Given Jacob’s study was conducted so long ago we also cannot be sure that extraneous variables were controlled (for example, distractions and pps IQ levels whilst doing the study).
• However, the study has since been repeated and the same results found suggesting the study does have validity.

Question 28

Miller (1956)

Answer 28

• Miller (1956) reviewed experiments into the capacity of short-term memory and concluded that it has a capacity of 7±2 items (the title of his famous paper, “The magical number 7±2”).
• He also said that memory capacity can be increased through a process called chunking.
• Miller found, for example, that people could remember 5 letters as well as they could remember 5 words.
• However, obviously the size of the chunk is very important.
• the bigger the chunk, the less that can be remembered
• Cowan (2001) reviewed research and argued Miller may have overestimated the capacity of the STM. - He concluded that the capacity of the STM was about 4 chunks (suggesting that the lower end of 7±2 items is more accurate)

Question 29

Coding definition

Answer 29

Coding can be defined as the form in which information is stored in the various memories

Question 30

3 possible ways information can be coded

Answer 30

Acoustic coding: storing information in terms of the way it sounds.
Semantic coding: coding information in terms of its meaning.
Visual coding: storing information in terms of the way it looks.

Question 31

How are things coded in STM & LTM

Answer 31

• Research has shown that information is mainly encoded in short term memory in acoustic (sound) form
• Information is mainly stored in long term memory on the basis of its meaning (semantics)

Question 32

Coding study

Answer 32

Baddeley(1966)

Question 33

Baddeley(1966) method

Answer 33

Participants were shown a sequence of 5 words under one of four conditions, and then immediately had to write them down in order:
1) Acoustically similar words (e.g. map, mad, cad, cap, cat)
2) Acoustically dissimilar words (e.g. pen, cow, pit, day, sup)
3) Semantically similar words (e.g. tall, high, broad, wide, big)
4) Semantically dissimilar words (e.g. foul, thin, late, safe, strong)

Question 34

Baddeley(1966) results & conclusion

Answer 34

results
- When tested immediately (a test of short term memory) participants were least accurate with the acoustically similar words- they commonly got them muddled
- words that are similar sounding are harder to remember acoustically - can’t distinguish between them so it shows STM acts acoustically
- When tested 20 minutes later (a test of LTM) participants were least accurate with semantically-similar words.
- words that mean the same are harder to remember semantically as it’s hard to distinguish - shows LTM codes semantically

conclusion
- Information is normally encoded acoustically in the STM (and therefore we find acoustically similar words harder to remember)
- semantically in the LTM (and therefore we are more likely to make mistakes remembering semantically similar words).

Question 35

Baddeley(1966) evaluation

Answer 35

strengths
Clear difference
weaknesses
Low ecological validity

Question 36

Baddeley(1966) - low ecological validity

Answer 36

• Unfortunately, Baddeley’s study has low ecological validity
• This means that the findings of the study cannot be applied to real life since the words give to the participants in this study were a meaningless list – they had no personal relevance to the participants. - As a consequence, this study does not tell us much about coding memories in everyday life
• Maybe semantic coding is used when information is more meaningful e.g. rather than looking at semantic memory through word lists, a more meaningful task should have been used in Baddeley’s study
• This means the results of the study have limited application to real life

Question 37

Baddeley(1966) - clear difference

Answer 37

Baddeley’s study does identify a clear difference in the coding of the two memory stores - the STM codes acoustically and the LTM codes semantically