MSM and Types of LTM

Define coding

How memory is stored

Define capacity

How much data can be held in a memory store

Define duration

How long memory is held within a store

What did Baddely (1966) discover about how each memory store is coded

• What do his findings suggest

STM is coded Acoustically

This is because when immediately recalling words in the correct order, p’s did worse with acoustically similar words than acoustically dissimilar words

LTM is coded Semantically

This is because after recalling words in the correct order after 20 mins, p’s did worse with semantically similar words

Outline Jacob’s 1887 research and findings on digit span (capacity)

• Researcher reads out 4 digits and P recalls them in the correct order

• Researcher continues to read out more digits if the P recalls them in the right order - until they’re incorrect

• This indicated the individual’s digit span

• Jacobs found that the mean digit span for all Ps was about 9.3, letters was 7.3.

Outline Miller’s 1956 research on span of memory and chunking

• Noted things came in 7s eg 7 days of the week, 7 deadly sins

• Miller thought the span of the STM is 7 items (plus or minus 2)

• Also noted that people could recall 5 words as easily as 5 letters - known as chunking

Define the STM

• What’s its coding, capacity and duration

The limited capacity memory store

• Coding - mainly acoustic

• Capacity - 5-9 items on average

• Duration - 18s

Define the LTM

• what’s its coding, capacity and duration

The permanent memory store

• Coding - mainly semantic

• Capacity - unlimited

• Duration - lifetime

Outline Peterson and Peterson’s 1959 study on the duration of the STM

• On each trial, students were given a consonant syllable to remember as well as a three digit number

• Students counted backwards from the number until told to stop - prevented mental rehearsal of the consonant syllable

• Each trial they were asked to stop after certain periods of time

What were the findings of Margaret and Lloyd Peterson's (1959) study on the duration of the STM

• After 3 seconds, average recall was 80%

• After 18 seconds it was about 3%

These findings suggested the duration of the STM was about 18 seconds, unless we repeat the information over and over

Outline Bahrick et al's 1975 research and results into the duration of the LTM

Procedure

• Compiled 392 American p's aged 17-74

• Recall was tested via (1) photo recognition test of 50 photos, some from their own yearbooks (2) free recall test, p's had to recall the names of those in their graduating class

Results

• Within 15 years were 90% accurate in photo recognition and 60% with free recall

• After 48 years of graduation were 70% accurate in photo recognition and 30% in free recall

Conclusion

LTM may last a lifetime for some material

Evaluate Baddely's research into the coding of the STM and LTM

Separate Memory stores

• Identified a clear difference between the two memory stores

• Although some research has shown exceptions to Baddely's findings, the fact that the LTM is coded semantically and the STM is coded acoustically has stood the test of time

• This was an important step in our understanding of the memory system

Artificial Stimuli

• Used quite artificial stimuli than meaningful material

• The words used had no personal meaning to p's. So it doesn't tell us much about coding in different types of memory tasks in every-day life

• This suggests the findings have a limited application

Evaluate the studies into Capacity

A valid study

• Jacob's study has been replicated

• Studies have been confirmed by Bopp and Verhaeghen in 2005 despite Jacob's study being in 1887 - so early research in psychology often asked adequate controls

• Shows Jacobs Jacob's study is a valid test if digit span in the STM

Not so many chunks

• Miller may have underestimated the capacity of the STM

• Cowan (2001) concluded the STM capacity is about 4 ± 2 chunks

• This suggests that the lower end of Miller's estimation(5 items) is more appropriate

Evaluate the studies into duration

Meaningless stimuli in the STM study

• Stimulus was artificial (limit)

• Study isn't completely irrelevant as we do sometimes memorise meaningless material (phone numbers)

• But recalling consonant syllables doesn't reflect everyday memory activity, so the study lacked external validity

High external validity

• Bahrick et al's. study had high external validity

• researchers investigated meaningful memories

• Suggests Bahrick's findings present a 'real' estimate into the duration of the LTM

What is maintenance rehearsal

Repeating information over and over again so it stays in the STM

Outline the MSM

• Proposed by Richard Atkinson and Richard Shriffin (1968,1971) and describes how information flows through a memory system

• It's made up of three stores: the sensory register (containing iconic and echoic stores), the STM and the LTM

• When we recall information from the LTM, it's called retrieval

Outline the Sensory register in reference to the MSM

• The memory stores for each of our five senses (iconic and echoic e.g)

• Coding the the iconic store is visual and acoustic for the echoic store (modality specific)

• The capacity is huge (millions of receptors)

• Duration is a very short time <1/2 a second

• You have to be paying attention for information to pass through onto other memory stores

What are the strengths of the MSM

Research support

• Support shows LTM and STM are different

• Baddely's 1966 experiment on coding showed how they're coded differently

• This suggests that there is a clear distinction between STM and LTM

What are the limitations of the MSM

More than one STM store

• Shallice and Warrington (1970) studied patient KF who had amnesia

• KF's STM for digits was very poor when they were read out loud, however recall was much better when he read them himself

• This suggests there is more than one type of STM store when processing different types of information

Lack of ecological validity

• Much of the research into the MSM uses artificial tasks such as recalling a string of digits/letters

• Baddeley (1966) used artificial stimuli instead of meaningful material

• This suggests there is a limited application to real world memory use

• The use of artificial tasks and application means that the study lacks ecological validity

Who proposed the MSM

Atkinson and Shriffin (1968/1971)

Outline the Episodic memory

• Our ability to recall events from our lives (places, people, objects and behaviours)

• These memories are complex and store how events relate to each other in time

• A concious effort is needed to recall episodic memories

• These memories are time stamped

• These memories are declarative and vulnerable to distortion

Outline the Semantic memory

• Contains knowledge of the world (facts and meanings)

• Memories aren't time stamped, we don't usually remember when we found out new concepts

• Less personal and more about facts

• Declarative and less vulnerable to distortion than episodic memory

Outline the procedural memory

• Memory of action and skills

• Recalled without conscious awareness or much effort (eventually)

• Abilities become automatic with practice

• Skills are difficult to explain

• Not time stamped, not declarative or vulnerable to distortion

What supports that there are different types of LTM

Clinical evidence

• Case studies of HM and Clive Weavering

• HM suffered from epilepsy and underwent brain surgery to correct this, removing his hippocampus

• The findings show that episodic memory was affected by brain damage, however semantic memory and procedural memory were not

• The case study of Clive Wearing who contracted a virus of the brain, shows that he was able toretain procedural memory (e.g. he could remember how to play the piano) but he did not retain episodic memories (e.g. he could not remember learning to play the piano)

Clinical evidence

• Brain scans indicate that each type of LTM may be stored in different areas of the brain

• Episodic memory is associated with the hippocampus

• Semantic memory is associated with the temporal lobe

• Procedural memory is associated with the cerebellum

• This clinical evidence is high in reliability as it is objective i.e. scientific

Which area of the brain is semantic memory associated with

Temporal Lobe

Which area of the brain is episodic associated with

Hippocampus

Which area of the brain is procedural memory associated with

Cerebellum

What are the limitations of evidence for different types of LTM

Counterpoint to Case Studies

• Case studies cannot be generalised beyond their immediate subject to the general population

  This weakens their use as supporting evidence for separate LTM stores as a sample of one participant cannot come near to being representative of a wider population

Conflicting neuroimaging evidence

• Buckner and Peterson (1996) reviewed evidence regarding the locations of semantic and episodic memory

• The concluded that semantic was located on the right side of the prefrontal cortex and episodic was on the right

• However other research links the the left of the prefrontal cortex with encoding episodic memories and the right for episodic retrieval (Tulving et al 1994)

• This challenges any neurophysiological evidence to support types of LTM as there is little agreement on where each is located