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LOOKING BACK
controversy concerning whether it was
necessary to assume more than one
memory system, with Conrad’s work
being cited as evidence for a temporary
acoustic system, in contrast to the more
stable system in long-term memory.
However, Conrad had not tested other
kinds of similarity, and so I decided
Alan Baddeley describes the origins of the multi-component model of
I would use words rather than letters
working memory
and, compare acoustic similarity with
similarity of meaning. My experimental
setup was rather basic, a room full of
volunteers, a noise source that could be
switched on or off and myself reading out
able to generate memorable codes for
sequences of five words. The results were
t is now more than 40 years since
every UK post town based on the letter
clear; a big effect of phonological
Graham Hitch and I published our
structure of English. By this time,
similarity, a small but significant effect of
paper proposing to extend the earlier
meaning, and no effect of noise level over
concept of short-term memory (STM) into however the Post Office had already
settled on the current system, so they
and above what could be accounted for
a more complex and ambitious working
by mishearing. My bosses Broadbent and
memory model (Baddeley & Hitch, 1974). were never used.
My work linking language structure
Conrad agreed that this was an interesting
We suggested replacing one STM system
to memory did, however, lead to my
result, theoretically if not practically, and
with three inter-related subsystems,
first short-term memory experiment,
I was encouraged to go ahead and explore
emphasising our assumption that its
demonstrating to three eminent Harvard
it further. The telephone project was
function was to hold information while
professors, George Miller, Gerry Bruner
passed on to Patrick Rabbitt who had just
working on it; a memory system that
and Leo Postman,
arrived at the Unit (using a
helps us to think. Our original model
that their paper
more sensitive method he was
remains at the centre of the current
showing an
able to show a small effect of
version (Baddeley, 2012). The
“What we found was more
influence of
noise). In collaboration with
multicomponent model did not, of
complex, and in the long
language structure
my friend Harold Dale, we
course, emerge fully formed. Hence I was
run more interesting”
on perception was
went on to demonstrate that
intrigued by the invitation to reflect on
in fact based on
the pattern changed
how it all began, and to supplement an
memory (Baddeley,
dramatically under standard longearlier account elsewhere, of the way in
1964a). Their paper was also criticised
term memory conditions, finding
which the model subsequently developed
by an up-and-coming young Canadian
meaning to be all important and sound
(Baddeley & Hitch, 2007).
psychologist, Endel Tulving. I pointed out
relatively unimportant. On the basis of
My first job involved working at
that he was wrong too (Baddeley, 1964b);
these results I began to conclude that
the MRC Applied Psychological Unit in
I seem to have been rather a pugnacious
there were two separate memory storage
Cambridge on the design of postcodes.
young man!
systems: a short-term system relying on
My supervisor was Conrad, currently
I was then switched to working
an acoustic code and a long-term system
best known for his discovery of the
based on meaning.
importance of acoustic similarity in verbal on finding an improved method for
measuring the quality of telephone links.
This view rapidly proved too simple;
short-term memory. He showed that
The idea was that the negative impact of
semantic effects can occur dramatically
errors in recalling strings of letters tended
a noisy signal would be exaggerated if the
in standard STM tasks such as memory
to be similar in sound to correct items
message had to be held in memory, hence
span; span for unrelated words is around
(e.g. b for v) and that sequences of
providing a more sensitive measure of the
five and for meaningful sentences nearer
similar-sounding items (e.g. b g v t c)
link. I speculated that the measure might
15. Furthermore, we must have
were harder to remember than dissimilar
be even more sensitive if the items to be
acoustic/phonological long-term memory,
(f k w j q). My task however, was
remembered were similar in sound –
otherwise how could we learn the sound
concerned with long-term memory for
Conrad’s acoustic similarity effect – and
of new words? The increasingly
postal codes. I applied the recently
proceeded to test this.
influential neuropsychological evidence
developed field of information theory to
By this time there was a very active
was also inconsistent with my simple
verbal long-term memory (LTM) and was
How it all began
references
I
334
Atkinson, R.C. & Shiffrin, R.M. (1968).
Human memory: A proposed system
and its control processes. In K.W.
Spence & J.T. Spence (Eds.) The
psychology of learning and motivation:
Advances in research and theory. (Vol.
2, pp.89–195). New York: Academic
Press.
Baddeley, A.D. (1964a). Immediate
memory and the ‘Perception’ of letter
sequences. Quarterly Journal of
Experimental Psychology, 16, 364–367.
Baddeley, A.D. (1964b). The redundancy of
letter-sequences and spaceinformation. American Journal of
Psychology, 77, 322.
Baddeley, A. (2012). Working memory,
theories models and controversy. The
Annual Review of Psychology, 63,
12.11–12.29.
Baddeley, A.D. & Hitch, G.J. (1974).
Working memory. In G.A. Bower (Ed.)
Recent advances in learning and
motivation (Vol. 8, pp.47–89). New
York: Academic Press.
Baddeley, A. & Hitch, G. (2007). Working
memory: Past, present… and future
query. In N. Osaka, R.H. Logie & N.
D'Esposito (Eds.) The cognitive
neuroscience of working memory
(pp.1-20). Oxford: Oxford University
Press.
Baddeley, A.D. & Warrington, E.K. (1970).
Amnesia and the distinction between
long- and short-term memory.
Journal of Verbal Learning and Verbal
Behavior, 9, 176–189.
Cermak, L.S. & Reale, L. (1978). Depth of
processing and retention of words by
alcoholic Korsakoff patients. Journal
of Experimental Psychology: Human
Learning & Memory, 4, 165–174.
Craik, F.I.M. & Lockhart, R.S. (1972).
Levels of processing. A framework for
vol 28 no 4
april 2015
looking back
UNIVERSITY OF STIRLING ARCHIVES
view. Despite earlier claims that amnesic
but processing it semantically and relating remembering strings of digits, while
patients showed semantic encoding
performing the various tasks that were
it to existing knowledge was by far the
deficits (Cermak & Reale, 1978), the
assumed to depend upon shortmost effective. Problems also came from
alcoholic Korsakoff patients on which
term/working memory. The longer the
neuropsychology, where patients with
this conclusion was drawn subsequently
digit sequence, we argued, the more STM
grossly impaired verbal STM were studied
proved to have subtle frontal lobe
capacity should be used up and the
by Shallice and Warrington (1970);
damage. Patients with a dense, but pure
greater the disruption.
according to the modal model, defective
amnesia showed no semantic encoding
What we found was more complex,
STM should lead to grossly impaired
difficulties (Baddeley & Warrington,
and in the long run more interesting
LTM, which it did not. Furthermore, if
1970).
than this. Concurrent digit load slowed
the system acted as a working memory,
I was not alone in my enthusiasm
performance down, but had an effect that
such patients should have massive
for exploring the field of short-term
was far from catastrophic. Hence in one
problems in their daily lives. They didn’t.
memory. Demonstrations of apparently
At this point many investigators into STM study people solved simple reasoning
clear differences between long- and shorttasks while holding from zero to eight
moved on to other more recently
term memory led to the generation of
digits, showing a nice
a large number of experimental
linear increase in
paradigms and many models. One
reasoning time,
book, for example, had 13 chapters
but performing at
each with a different model. One
a consistent five per
model, however, became dominant,
cent error rate
so much so as to be named the ‘modal
regardless of load.
model’. This model was proposed by
We showed similar
Atkinson and Shiffrin (1968), who also
effects in studies of
claimed it to be a working memory
verbal memory and of
model which, in addition to providing
prose comprehension.
short-term storage, was capable of such
Our attempt to
complex activities as selecting
account for this
strategies, controlling input to LTM,
pattern of results
guiding retrieval and much else. The
resulted in three
model was also expressed
proposed components
mathematically, although the examples
that still form the
provided were limited to the learning
core of the
of meaningless verbal items.
multicomponent
By the end of the 1960s however,
model, namely
problems with the modal model were
an attentionally
starting to emerge. The assumption
limited control system
that material held in the short-term
(the central executive),
The research started at Sussex, but was continued and
store would automatically transfer to
a system for holding
published from Stirling
LTM, with duration in store linked to
sequences of
amount learned, proved unjustified.
acoustic/speech-based information
developing areas, such as levels of
Failure to address the issue of type of
(the phonological loop) and its visual
processing and semantic memory.
material and method of encoding created
equivalent (the visuo-spatial sketchpad).
It was at this point, with me at the
even more problems. These came to a
At this point I received an invitation
age of 37, that my head of department
head with a paper by Craik and Lockhart
to submit a chapter to an influential
gently suggested I should perhaps
(1972), who introduced the concept of
annual series entitled Recent Advances in
consider seeking my first research grant.
levels of processing whereby learning
Learning and Motivation (It is interesting
I applied to work on the link between
depended on what was done with the
to reflect that if this happened today, our
long- and short-term memory, asking for
material rather than how long it was held
head of department would strongly advise
a postdoc and a research assistant. The
in STM. For example, processing a word
against publishing in a volume that would
committee decided it was too expensive
in terms of its visual appearance led to
not be eligible for the REF and would not
but happily cut the research assistant not
poor retention, making a phonological
register on the SCI citation count. Instead
the postdoc, Graham Hitch. I knew
judgement about it improved retention,
we would have had to publish as a series
Graham as a master’s student, converting
of separate papers, in each case struggling
from a Cambridge physics degree to
with sceptical referees concerned at our
experimental psychology. He had just
excessive speculation.) We hesitated; the
finished a PhD under Donald Broadbent
model was clearly not yet complete (it
on STM, and proved (and still proves)
memory research. Journal of Verbal
still isn’t!), but it seemed too good an
to be an ideal colleague and collaborator.
Learning & Verbal Behavior, 11, 671–684.
opportunity to miss and Baddeley and
It seemed an inauspicious time to
Shallice, T. & Warrington, E.K. (1970).
Hitch (1974) duly appeared. We would
be entering the field of STM, given its
Independent functioning of verbal
have been amazed – indeed, I am still
problems and the fact that we did not
memory stores: A neuropsychological
study. Quarterly Journal of Experimental
amazed! – that it would still be cited four
have access to patients with the STM
Psychology, 22, 261–273.
decades later.
deficits that were so theoretically
important. Happily, we hit on the idea of
turning our students into ‘patients’, not by I Alan Baddeley is Professor of Psychology at
removing chunks of their left hemisphere,
the University of York
but by keeping it occupied in
[email protected]
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