STM/LTM
1. Explain what is meant by duration of STM (2 marks)
Duration is the length of time information can be held in memory. The duration of the
short-term memory is up to 30 seconds.
2. Explain what is meant by coding in LTM (2 marks)
Coding is the format in which information is stored in the various memory stores. The
long-term memory is coded semantically (meaning)
3. Outline one research study into the duration of LTM. In your answer include
what the researchers did and what they found (4 marks)
Bahrick (1975) investigated the duration of long-term memory using 392 American university
graduates. The graduates were shown photographs from their high-school yearbook and for
each photograph participants were given a group of names and asked to select the name
that matched the photographs. Bahrick found that 90% of the participants were able to
correctly match the names and faces, 14 years after graduating and 60% of the participants
were able to correctly match the names and faces 47 years after graduation. Bahrick
concluded that people could remember certain types of information, such as names and
faces for almost a lifetime. These results support the multi-store model and the idea that our
long-term memory has a lifetime duration (at least 47 years) and is semantically encoded.
4. Outline + evaluate research related to the features of STM (coding, capacity,
duration) (16 marks)
STM capacity is limited to 7+/-2 and as a result,information can get displaced if new
information enters the STM. This was investigated by Miller and Jacobs. In 1956, Miller
proposed that the capacity of the STM was 7 items. Miller also found that if you group items
together it makes them easier to remember and increases capacity of your STM, for
example, when remembering a phone number, by splitting the 11 digits into 3 or 4 chunks
makes it easier to remember. Jacobs developed the digit span technique to measure the
capacity of the STM. The researcher gives the ppt 4 digits, then they have to recall
Cowan reviewed various studies and concluded the STM was limited to 4 chunks, which is
closer to the lower end of Miller’s estimate. This is a limitation to Miller's research as it shows
Miller overestimated the capacity of the STM. Therefore the STM is more limited than first
predicted. Jacobs also found that recall (digit span) increased steadily with age. The mean
for 8 year olds is 6.6 and for 19 year olds is 8.6. Jacobs’ experiment lacks validity as it was
conducted a long time ago (1887) and so the experiment might have not been conducted in
the most effective way as early research in psychology lacked adequate control, for
example, participants may have been distracted while they were being tested so didn’t
perform as well as they might have. This would lead to invalid results because there were
confounding variables that were not controlled. However, the main issue with this is that
Jacobs initially didn’t take into consideration the individual differences and generalised his
results. Now we understand that the difference occurs because the brain develops with age
along with memory.
,STM duration is limited up to 30 seconds and as a result information can decay if not
rehearsed. STM duration was investigated by Peterson + Peterson who conducted an
experiment where participants had to recall consonant syllables (trigrams - 3 letters with no
meaning) and to prevent rehearsal, participants had to count backwards in threes or fours
until told to stop from a set 3-digit number. Each participant had 2 practice trials followed by
8 trials - where the retention interval was different each time.The Petersons found that the
longer the interval delay was, the less trigrams were recalled. Participants were able to recall
80% of trigrams after a 3 second delay. However, after 18 seconds, less than 10% of
trigrams were recalled correctly, showing that the STM has a limited duration when rehearsal
is prevented (20 seconds at most).
This research is limited as demonstrated by Marsh et al. (1997), who found that STM
duration was a lot shorter when participants weren’t expecting to be tested after the interval.
This is a limitation as participants in the Peterson and Peterson experiment would have
known it was a memory task as it was a lab experiment, making them more prone to
demand characteristics. This therefore suggests that duration may be shorter than first
anticipated without rehearsal, as the experiment was unreliable due to the lack of internal
validity. Another limitation of this study is that the stimulus was artificial. Trying to memorise
consonant syllables does not reflect most real-life memory activities where what we are
trying to remember is meaningful, so this study lacks external validity. However, we do
sometimes try to remember meaningless things such as phone numbers, so it is not entirely
irrelevant.
Coding in the STM was investigated by Baddley who tested the effects of acoustic and
semantically similarity on STM recall. He gave participants lists of words which were
acoustically similar or dissimilar and words that were semantically similar or dissimilar.
Baddeley found that participants had difficulty remembering acoustically similar words when
asked to recall them straight after (STM recall) showing that we encode in terms of the way
words sound (acoustically).
However, this research is limited because the stimuli used is artificial rather than meaningful
material. The word lists had no personal meaning to the participants, meaning we should be
cautious about generalising the findings to different types of memory tasks. For example,
when processing more meaningful information, people may use semantic coding even for
STM tasks, suggesting that findings from this study have limited application. Another
limitation includes research from Brandimote et al. (1992) that participants used visual
coding in STM if given a visual task and prevented from doing any verbal rehearsal. This
suggests that we can code things visually when we need too,
MSM
1. Explain what is meant by the term multi-store model (2 marks)
A representation of how memory works in terms of 3 stores called sensory register, STM and
LTM. It also describes how information is transferred from one store to another, how it is
remembered and forgotten.
, 2. Explain what is meant by the term sensory register (2 marks)
The memory stores for each of or 5 senses, such as vision (iconic store) and hearing (echoic
store). Coding in the iconic sensory register is visual and in the echoic register is acoustic.
The capacity of sensory registers is huge and information lasts for a very short time.
3. Outline the multi-store model (6 marks)
The multi-store model consists of the sensory register, STM and LTM. It describes how
information flows through the memory system. For example, a stimulus from the
environment will pass into the sensory registers (with 2 main stores, echoic memory and
iconic memory). If the person was paying attention, the information will go through to the
STM, and if rehearsed enough, will go through to the LTM.
The short term memory is known as a limited capacity store because it can contain a certain
number of things before forgetting. The capacity of the STM is thought to be around 7+-2.
Information in the STM is coded acoustically and lasts about 30 seconds unless it is
rehearsed. Maintenance rehearsal occurs when we rehearse material to ourselves over and
over again. We keep the information in our STM as long as we rehearse it, if we rehearse it
enough, it passes into long-term memory.
The LTM is the potentially permanent memory store for information that has been rehearsed
for a prolonged time. It is believed that the capacity is unlimited e.g. Bahrick found that
participants were able to recognise names and faces of their school classmates almost 50
years after graduating. LTMs tend to be coded semantically. When we recall information
from the LTM, it has to be transferred back into STM by a process called retrieval. No
memories are recalled from the LTM store directly.
4. Outline two limitations of the MSM (4 marks)
One limitation of the MSM is that there is evidence showing how the STM may not be a
unitary store. Evidence for this includes people suffering from a clinical condition called
amnesia shows that. For example, Shallice and Warrington studied a patient with amnesia
called KF and found that his STM for digits was very poor when they read them out loud to
him. But his recall was much better when he was able to read them out loud to himself.
Further research from people with amnesia showed that there could be another short-term
store for non-verbal sounds (noises). The unitary STM is a limitation of the MSM because
research shows that there must be one short-term store to process visual information and
another to process auditory information. The working memory includes these separate
stores.
Craik and Watkins found that there may be more than one type of rehearsal. Maintenance
rehearsal is the type of rehearsal described in the MSM, but this does not transfer
information into the LTM, it just maintains it in the STM. Elaborative rehearsal is needed for
long-term storage, this is when you link the information to your existing knowledge. This is a
very serious limitation of the MSM because it is another research finding that cannot be
explained by the model.
Another limitation of the MSM is that most of the research used to support it include artificial
materials, meaning it lacks internal validity. In everyday life we form memories related to all
