The multi-store model of memory

Sensory register Short term memory Long term memory Features of each store: coding, capacity and duration Evaluation

Who proposed the MSM?

Atkinson and Shiffrin (1968)

What are the 3 stores of the MSM?

Sensory register, STM, LTM

Sensory register

This store is not under cognitive control unlike the STM and LTM

The sensory register contains one sub-store for each of the 5 senses e.g. an echoic store for auditory information.

Since it receives information for our senses, the sensory register has a huge capacity, but a duration of less than half a second.

Therefore, information will only pass from the sensory register to the short-term memory store if we pay attention to it.

STM

STM is described as being acoustically encoded (Baddeley), having a capacity of 7+/- 2 items (Miller) and a duration of 18-30 seconds (Peterson).

Maintenance rehearsal occurs when we repeat the new information to ourselves, allowing the information to be kept in the STM.

Prolonged maintenance rehearsal allows the information to pass into the LTM, whilst a lack of such rehearsal causes forgetting.

LTM

LTM is described as being semantically encoded (Baddeley), having an unlimited capacity and a very long duration (over 46 years, as shown by Bahrick et al).

In order to remember information, ‘retrieval’ must occur, which is when information is transferred back into the STM, and will continue to pass through the maintenance loop afterwards.

Coding EV/AO3 for LTM

Baddeley (1996) - gave four 10 word lists to four participant groups

A - acoustically similar- words sound the same

B - acoustically dissimilar - word sound different

C - semantically similar - have related meaning

D - semantically dissimilar - words are unrelated

It was found immediate recall was worst for list A and recall after 20 mins was worst with list D

This suggests …that the coding in LTM is semantic, as recalling list C was most difficult as the recalling similar meanings caused confusion in recall

Duration for LTM EV/AO3

Bahrick (1975) - 400 participants aged 17 - 74 were tested for memory of old photographs (recognition task) and names (free recall task) of their school friends.

It was found recall in matching names to face was 90% after 15 years, and still 60% for names after 48 years

This suggests the duration of LTM is very large, potentially limitless.

Recognition is easier than recall > LTM holds a lot of information but we need some clues in order to be able to access it

Coding for STM EV/AO3

Baddeley (1996) - gave four 10 word lists to four participant groups

A - acoustically similar- words sound the same

B - acoustically dissimilar - word sound different

C - semantically similar - have related meaning

D - semantically dissimilar - words are unrelated

It was found immediate recall was worst for list A and recall after 20 mins was worst with list D

This suggests …that the coding in STM is acoustic, as recalling list A was most difficult as the recalling similar sounds caused confusion in recall

Capacity STM

Jacobs (1887)

Participants were presented with lists of letters or numbers.

Participants then had to recall the list

It was found that the capacity for letters was on average around 7 items for letters and 9 for numbers (usually stated 7±2).

This suggests that the capacity of STM is very limited.

Miller suggested this can be improved by chunking, making small sets/groups of items, this reduces the total number of items overall

Duration STM

Peterson + Peterson (1959)

They showed participants three letter trigrams (e.g. HFD, TKU).

Then participants had to count backwards for a few seconds to stop maintenance rehearsal (interference task)

It was found after 18 seconds recall was less than 10%

This suggests that unless maintained information is held in STM for only a few seconds (18-30 seconds max) before it disappeared

However, some participants got confused earlier trigrams with later ones which shows there is some duration which is longer

Evidence that the STM and LTM stores are separate processes

The clinical case study by Shallice and Warrington on KF supports the idea that STM and LTM are separate stores because KF had a poor STM after a bike crash, but his LTM remained good.

However, they found that actually his STM could recall visual information, but it could not handle verbal information- this highlights a key limitation of MSM in that STM is more than one store and this is not shown in the model. 

Furthermore, Milner found similar results in the case study of HM who could add procedural memories to his LTM but not episodic. 

Consequently, LTM must also be more than one store.