Multi- Store Model of Memory

Baddeley (1966) presented participants with four different lists of words

• Acoustically similar
• Acoustically dissimilar
• Semantically similar
• Semantically dissimilar

Participants had to recall the words in the correct order and when they had to do the recall task immediately after hearing it (STM recall) they tended to do worse with acoustically similar words.

If participants were asked to recall the words after 20 minutes (LTM) they tended to do worse with semantically similar words.

Baddeley proposed that STM codes acoustically due to the acoustic confusion and that LTM codes semantically due to semantic confusion.

LIMITATION

Baddeley's study did not use meanigful material as the words in the study had no personal meaning to any of the participants.

Therefore, when processing more information, people may use semantic coding even for STM tasks.

This means that the results of this study have limited application and we should be cautious about generalising the findings to different kinds of memory task.

Jacobs (1887) tested STM capacity with the serial digit soan method where the participants are presented with increasingly long lists of numbers or letters and have to recall them in the right order.

When participants fail on 50% of the tasks, they are judged to have reached their capacity. Jacobs found capacity for numbers was nine items and for letters was seven items, which illustrates how the capacity of STM is limited.

LIMITATION

Jacobs' study was conducted a long time ago and early research in psychology often lacked adequate control of extraneous variables.

For example, some participants may have been distracted while they were being tested so they maybe didn't perform as well as they could have.

This would mean that the results may not be valid because there were confounding variables that were not controlled, however these results have been confirmed in other research supporting its validity.

Miller (1956) gave participants lists of of either numbers, letters, words or tones and they were then asked to recall as many as possible.

Miller noticed that participants could recall on average 7 +/- 1 or 2 items. This became known as Millers magic number- the capacity of STM.

Peterson and Peterson (1959) made participants listen various trigrams (e.g. XPJ, ZFB) .

The control group were immediately asked to recall as many as possible while the experimental group were first given a distractor task of counting backward's in three's so that the rehearsal of the trigrams was prevented, before asking them to recall as many as possible.

Whilst the control group were able to score on average 75% correctly recalled trigrams, the experimental group who had an 18 second delay had a recall average of 6%.

This shows that the duration of STM without rehearsal is between 15 and 30 seconds.

LIMITATION

When this study was conducted the participants were asked to memorise consonant syllables that do not reflect most real-life memory activities where we would try to remember something that is meaningful.

Therefore, it could be argued that this study lacked external validity but on the other hand, we do sometimes try to remember fairly meaningless things, such as phone numbers.

This means that the study was not totally irrelevant.

Bahrick (1975) tested participants up to the age of 74 on the memory of former classmates.

Thus demonstrating that memories can be accurate for a very long period of time.

STRENGTH

The study that Bahrick conducted high external validity because real-life meaningful memories were studied.

When lab studies are done with meaningless pictures to be remembered, recall rates were lower.

The down-side of such real-life research is that confounding variables are not controlled, such as the fact that Bahrick's participants may have looked at their year book photos and rehearsed their memories over the years. This is known as the Serial position effect.

STRENGTH

There is evidence to support the fact that STM and LTM are different stores as Murdock (1962) presented participants with words from a list at a rate of one per second.

They then had to immediately free recall as many as they could remember.

Words that appeared at the beginning (primacy) and words at the end (recency) of the list were recalled more often than words in the middle of the list.

The words at the beginning of the list were more likely to have been rehearsed and transferred into the LTM whereas words at the end of the list were still in the STM.

Those in the middle were lost.

STRENGTH

The distinction between STM and LTM is supported by real-life case studies of amnesic patients.

Shallice and Warrington (1970) reported the case of KF, a young man who sustained brain injuries after a motorcycle accident.

He had impaired STM working alongside a fully functioning LTM.

LIMITATION

Research supporting the MSM uses artificial materials as researchers often asked participants to recall digits, letters and sometimes words.

However, in everyday life we form memories related to all sorts of useful things- people's faces, their names, facts, places, etc.

This suggests that the MSM lacks external validity and that research findings may reflect how memory works with meaningless material in lab testing but does not reflect how memory works in everyday life.

LIMITATION

There is a lot of research evidence that LTM is not a unitary store.

We have one LTM store for memories of facts about the world (semantic), and a different one for memories of how to ride a bike for example (procedural).

The MSM is limited because it does not reflect these different types of LTM.

LIMITATION

Evidence also suggests that there is more than one type of STM.

Shallice and Warrington (1970) found that KF was able to recall digits that he read himself compared to when they were read to him.

This suggests that there must be a separate store for processing visual information and another for processing auditory information.

The working memory model is a better explanation for this finding because it includes separate STM stores.