MEMORY: Short and long term memory - psychology

AO1 - capacity of the STM Jacobs and miller

can be assed using a digit span

Joesph Jacobs used this technique to asses STM capacity. He found that average span for digits was 9.3 items and 7.3 for letters. Jacob suggests that it may be because there are only 9 digits where as there are 26 letters.

One of the earliest studies in psychology -

According to Miller STM has a capacity of about 7 items - sometimes a bit more, sometimes a bit less (7+-2), meaning most people can hold between 5 to 9 pieces of information. He noted that people can count 7 dots flashed onto a screen but not many more.

He also suggested that STM capacity can be increased through a process called chunking, where individual items are grouped together into meaningful units or chunks - people can recall five words as well as they can recall 5 letters

capacity ?

how much can be held in memory measured in bits of information -how much can be held in the memory store. STM has a limited capacity store where as LTM has a potentially limitless capacity.

duration

how long a memory lasts before either is no longer available

coding

format in which information is stored in sounds (acoustic), visually and in its meaning (semantic)

STM

memory for an immediate event measured in seconds and minutes rather than hours and days. A limited capacity in about 4 chunks, also known as working memory.

LTM

your memory for events in the past measured in days, weeks and years. The duration potentially being a lifetime

AO3 of STM capacity Cowen

One criticism of the research investigating STM is that millers original findings have not been replicated -

Cowan (2001) reviewed a variety of studies on the capacity of the STM and concluded that STM is likely to be limited to about 4 chunks.

Research on the capacity of the STM for visual information (rather than verbal stimuli) also found that 4 items was about the limit. This means that the lower end of Millers range is more appropriate.

This matters because the original findings have not been replicated by subsequent studies and suggests that STM may not be as extensive as we thought

AO3 on STM Jacobs

The capacity of the STM is not the same for everybody so has individual differences

Jacobs 1887 found that recall (digit span) increased steadily with age - 8 year olds could remember an average of 6.6 digits, whereas 19 year olds could remember on average 8,6 digits

this increase with age might be due to a gradual increase in brain capacity or it may be that people develop strategies to improve their memory as they get older.

this suggests that we can’t make full generalised conclusions about the capacity of the STM, reducing the validity of theories about STM and its capacity.

AO1 - duration of the STM Peterson and Peterson

Peterson and Peterson 1959 studied the duration of the STM, using 24 students. Each participant as tested over 8 trials. On each trial a participant was given a consonant syllable and a 3 digit number (e.g. THX 512) they were asked to recall the consent syllable after a retention interval of 3,6,9,12, 15 or 18 seconds.

During the retention interval they had to count backwards from their 3 digit number

participants on average were 90% correct over 3 seconds, 20% correct after 9 seconds and only 2 % correct after 18 seconds

This suggests that the STM has a very short duration - as long as verbal rehearsal is prevented.

AO1 duration of LTM bahrick et al

Barrack et al tested 400 people of various ages (17-74) on their memory of classmates. A photo recognition test consisted of 50 photos, some from the participants high school yearbook. In a free-recall test participants were asked to list the names they could remember of those in their graduating class.

Participant’s who were tested within 15 years of graduation were about 90% accurate in identifying faces. After 48 years, this declined to about 70% for photo recognition.

Free recall was about 60% accurate after 15 years , dropping to 30% after 48 years/ (free recall. = naming classmates without prompts)

this shows that LTM can last for decades, especially when cues are provided and supports the view that info in LTM is not lost easily, even over very long periods

AO3 - Research of STM - lacks mundane realism/ artificial

the testing methods are artificial

trying to memorise consonant syllables does not truly reflect most every day memory activities

although it must be noted that we do occasionally try to remember fairly meaningless things, such as phone numbers or postcodes

this means that the study has some relevance to everyday life but slightly lacks mundane realism because it deosn’t reflect memory activities

AO1 - coding

information that we store has to be ‘written’ in memory in some form - it is described as a ‘code’ which is held in the form of sounds (acoustic), images (visual) or meaning (semantic)

Acoustic and semantic coding

• cat, cab, can, cap, mad, max, mat, man, map - words are acoustically similar but semantically different

• great, large, big, huge, broad, long, tall, fat, wide - opposite to above, semantically similar but acoustically different

Alan BADDELEY used word lists like those above to test the effects of acoustically and semantic similarity on STM and LTM. He found that participants had difficulty remembering acoustically similar words in STM but not in LTM, whereas semantically similar words posed little problem for STMs but led to muddled LTMs

This suggests that STM is largely encoded acoustically whereas LTM is largely coded semantically.

AO3 for LTM frost coding

Criticism may be that LTM may not be exclusively semantic

Frost 1972 showed that long term recall was related to visual as well as semantic categories.

Nelson and Rothbart found evidence of acoustic coding in LTM which suggests our Brian stores information in different ways, not just by its meaning (semantic). Visual images may help memory by creating extra connections, making it easier to remember.

therefore it seems that coding In LTM is not simply semantic but can vary according to circumstances

Strength/ limitation of Barracks study into LTM

• the task of recalling the names of college students is more relevant to real life meaning it has external validity.

• however this real life research means that it is difficult to control factors such as some people rehearsing names or continuing to live in the same town and potentially bumping into classmates over the years giving them a chance to rehearse the names, thus aiding the call of some participants

AO3 for LTM - baddely limitation

Baddeleys methodology has been criticised

in the study by Baddeley, STM was tested by asking participants to recall a word list immediately after hearing it. LTM was tested by waiting 20 minutes. It is questionable as to whether this is really testing LTM.

This casts doubt on the validity of Baddeleys research because he wasn’t testing LTM effectively.

summary of this

Peterson & Peterson - only 2% could remember after 18 seconds 

Miller magic number 7 +/- 2

Bahrick - 15 years recalled 90% 48 yrs 70%

Photos: Without photos recall was 60% after 15 years and 30% at 48 years.