Long term memory (LTM)
is vast. As far as we know capacity has never been reached, but
don’t worry the term is still young! However, it’s unlikely that
you’ve ever heard anyone complain that they need to delete a few
memories before they can store anything new! As far as I’m aware
nobody has tried to estimate capacity, but Solso (1991) compares it
favourably with the largest computers.
factoid for you to contemplate. In 1973 Petr Anokhin of Moscow
“We can show
that each of the 10 billion neurons in the human brain has the
possibility of connections to 1 with 28 noughts after it; that’s
10,000,000,000,000,000,000,000,000,000 connections! It means that
the total combinations in the brain, if written out, would be 1
followed by 10.5 kilometres of noughts!
psychologists have studied memory is to experiment on themselves.
The beautifully named Marigold Linton kept a detailed diary
recording daily events and facts about flowers etc on cue cards over
many years. Each day was represented by a single word. When given
the cue word she was able to recall with 70% accuracy all the events
and information recorded for that day even 7 years later.
Bahrick et al
Year Book study (1975)
aged between 17 and 74 were tested on their memory of school
friends. A number of different tests were carried out including a
free recall of all the names of classmates they could remember,
recognition of classmates from a selection of 50 photographs, a name
recognition test and a photo matching test.
In order to
check accuracy of recall the researchers used year books for the
relevant year groups of the participants.
that had left school up to 34 years previously, accuracy of recall
on the face and name recognition tasks was still an amazing 90%.
Even for participants who had left school 48 years previously it was
Recall can be
accurate over a very long period of time, leading to the term vLTM
(very long term memory) to describe this phenomenon.
used is a field experiment so is much higher in ecological validity
since this is far more similar to the purpose we generally use our
study was poorly controlled. The researchers assumed that last
contact with their classmates would have been when they left
school. Little consideration seems to have been made of
participants seeing classmates in the intervening years or even of
them having looked through yearbooks themselves!
Only one type of
recall (visual) was tested. It could even be argued that
recognition of this sort is not recall as such anyway!
Evidence for two
memory stores (STM and LTM)
This is a favourite on examination papers. Clearly you could talk about
research into the two main memory stores mentioned above. In addition
to this it would be essential to mention some, if not all, of the
Multistore model of
Discussed in the next section, this would be a good start to the essay
since it suggests how the two main stores work in conjunction with one
gave 103 psychology students lists of words to free recall (in any
order) in 90 seconds. Typically words at the start of the list and
especially those at the end tended to be recalled most often. This was
explained by words at the start being rehearsed from STM into LTM
creating a stronger trace and those at the end still being present in
STM when recall begins. Evidence for two separate stores.
Most people with
memory problems have either impairment of their STM or LTM, not usually
both. This suggests that they are different systems.
HM (or Henry
The classic case
is that of H.M who at the age of 27 underwent surgery in an attempt to
cure his epilepsy apparently triggered by a cycling accident when he was
nine. A surgeon, William Scoville removed both his temporal lobes
including a structure known as the hippocampus (Latin for sea horse) and
an area known to be crucial to memory.
procedure HM was unable to create new long term memories (anterograde
amnesia) and lost some of his existing LTM retrograde amnesia). However
his STM remained intact with a normal capacity and duration, limited
only by his inability to rehearse.
HM is still alive
today, now in his early eighties and being cared for in a residential
home in Connecticut (Wikipedia) he is still being studied by cognitive
psychologists! HM’s pattern of
memory loss is not unusual. Clive Wearing suffered a similar form of
amnesia following a herpes simplex (cold sore) infection that spread to
areas of his temporal lobes.
both cases and in most cases of amnesia affecting LTM it is mainly
episodic memory that is lost, the ability to recall memories of events
and certain factual information such as faces, dates etc. So called
semantic memory is largely unaffected so patients can still use
language, walk, cycle etc. and still retain an understanding of ‘how
could be taught new skills, which over time would improve with
practice. However, he would have no recollection of ever having
performed them before!
KF who suffered
damage to his STM following a motorcycling accident still retained a
near normal LTM. However, yet again the situation wasn’t quite that
simple since KF could still recall visual information using his STM but
struggled with auditory and verbal information, making conversation
tell us about memory
We therefore have
a situation were cases of amnesia can both support the idea of two
memory stores whilst at the same time question the idea. This is
particularly good stuff to include in a discussion of the existence of
two memory stores.
Two memory stores
Amnesiacs tend to lose only one store
(either STM or LTM) supporting the idea of two separate stores
presumably located in different brain areas or structures.
More than two stores
However, HM and Clive Wearing both
provide us with evidence that LTM is more complex and seems to comprise
at least two components (semantic and episodic LTM). More on this
when we look at types of LTM. Similarly KF suggests that STM is
also more complicated having separate stores for both auditory and
visual information. See later section on working memory.
This is explained
in later sections and argues that STM may not be just one store but a
collection of components each with a different task. This would be
evidence for there being more than two stores.
techniques have found that different areas of the brain operate when
different stores are being used providing best evidence for different
memory types. The prefrontal cortex is active when STM (now more
correctly referred to as working memory) is being used whereas the
hippocampus in the temporal lobes is active for LTM.
areas known to be involved in LTM
Types of Long term memory
First a note of
caution. ‘Types of long term memory’ is not specifically mentioned in
the specification, nor do some of the texts, e.g. Cardwell for AS cover
the topic. However, some texts, including ours, do and the wording in
the specification is sufficiently woolly to allow a question on it. To
date no questions have been set on the topic, however, information
contained in this section and covered in class will at the very least be
useful in part c questions that deal with STM and LTM.
saw in the videos on amnesia that many patients suffering memory loss
still have vital aspects of their LTM intact. It is very rare for
amnesiacs to lose their memory for skills such as language (reading and
writing) and for walking, swimming etc. As we saw in the case of Clive
Wearing his ability to play the piano and conduct choirs was still
intact despite most other memories having been lost. In the video his
long suffering wife says that his episodic memory is severely
impaired whilst his semantic memory is largely intact. This is
one way of distinguishing types of LTM, however, there are others: What
follows is a brief summary of these, with examples and similarities
drawn between them.
Semantic (Tulving 1972)
memory contains the details of your life. When Victoria Beckham
gets someone to write her autobiography for her she would first sit
down and tell them, presumably in words of not more than two
syllables, all the interesting events that have happened to her.
For example the chive she had for dinner each day in August and the
counselling she received on discovering she had a split end!
memory contains our memories of the World and how it works.
Continuing the theme, hubbie Dave would store here his vast
knowledge of the English language, capital cities of the World
(presumably so they can name their next son Ulan Bator), and most
importantly his footballing skills, specifically how to bend it
like… well Beckham!
(1989) using radioactive gold, found different areas of the brain are
active when the two memory types are being used. Episodic engages the
frontal lobes, semantic the posterior lobes.
Procedural (Cohen and squire 1980)
(knowing that). For example knowing capital cities and other
factual information and knowing about personal events in our life.
This is different to Tulving who believed that these two types of
information were stored in different aspects of LTM.
This covers our knowledge or memory for skills such as walking,
talking, driving, playing football etc.
Squire et al
(1992) used PET scans to show that different areas of the brain were
active during each memory type.
Explicit (Graf and Schacter 1985)
declarative and being used for memories that we have to consciously
recall, for example we need to think about personal memories and
memories for trivia.
similar to procedural and being used for memories that we don’t have
to consciously think about. These are mostly skills such as walking
and talking. If we do consciously think about such activities e.g.
driving, they can become more difficult.
is particularly useful in explaining amnesia in brain-damaged patients,
typically these having damage to their explicit memory but retaining an
intact implicit memory. (E.g. H.M. and Clive Wearing).
Wearing and wife Deborah