Long And Short T,erm Memory

Question 1

What is short-term memory?

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

What is long-term memory?

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

What are the three different ways, short-term and long-term are different

Answer 3

Duration capacity and coding

Question 4

What is duration?

Answer 4

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

Question 5

Describe a study for the duration of short-term memory

Answer 5

Peterson and Peterson (1959)
1) Participants (24 undergraduate students) were presented with a consonant trigram (3 random consonants) e.g. ZFB
2) They were then asked to count backwards in threes to stop them repeating/rehearsing the consonant trigram.
3) After intervals of either 3, 6, 9, 12, 15 or 18 seconds, participants had to stop counting and repeat the trigram.
4) This was repeated using different trigrams

Question 6

What were the results and conclusion of Peterson and Peterson study?

Answer 6

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 7

Strength of Peterson and Peterson study

Answer 7

• 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 8

Weakness of Peterson and Peterson study

Answer 8

• 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).
• 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 9

What is the overall conclusion of the duration of the short term memory?

Answer 9

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

Question 10

Describe the study of the long-term memory duration

Answer 10

The duration of the LTM was also tested to see how long these memories last. Bahrick and his colleagues tested this.

Bahrick et al (1975)
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.

Question 11

What are the results/conclusion of Bahrick study?

Answer 11

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. This 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 12

Strength of Bahrick study

Answer 12

• Bahrick’s experiment has high external validity – 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 13

Weakness of Bahrick study

Answer 13

• 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.
• 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 14

describe the study for the capacity of the short-term memory

Answer 14

The capacity of the STM was measured by Jacobs.
Jacobs (1887): developed the serial digit span technique. The 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.

Question 15

Results of Jacob study

Answer 15

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 16

Weakness of Jacobs research

Answer 16

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.
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.
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 17

Describe Miller’s findings in the capacity of short-term memory

Answer 17

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. Cowan (2001) reviewed research and argued Miller may have overestimated the capacity of the STM. He conclude that the capacity of the STM was about 4 chunks (suggesting that the lower end of 7±2 items is more accurate)

Question 18

What is coding

Answer 18

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

Question 19

What are the three possible ways information can be coded?

Answer 19

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 20

How is information in the short-term and long-term memory coded

Answer 20

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). Evidence to support this comes from Baddeley (1966)

Question 21

Describe an experiment to find the coding of short-term memory -baddeley

Answer 21

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 22

Results of baddley experiment

Answer 22

When tested immediately (a test of short term memory) participants were least accurate with the acoustically similar words- they commonly got them muddled.
When tested 20 minutes later (a test of LTM) participants were least accurate with semantically-similar words.

Conclusion: Information is normally encoded acoustically in the STM (and therefore we find acoustically similar words harder to remember) and semantically in the LTM (and therefore we are more likely to make mistakes remembering semantically similar words).
However information can be stored in the STM and LTM in other forms .e.g. visually.

Question 23

Weakness of baddeley study

Answer 23

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 24

Strength of baddeley study

Answer 24

However, on a more positive note, Baddeley’s study does identify a clear difference in the coding of the two memory stores!!