Lecture 1: Short Term and Working Memory Outline

1
Lecture 1 Short Term and Working MemoryOutline

• What is memory?
• The Short Term / Long Term distinction
• Baddeleys model of Working Memory
• Evidence for Baddeleys model
• The episodic buffer
• By the end of the lecture you should be able to
  appreciate
• The importance of memory in our everyday lives
• Why a distinction is made between short and long
  term memory
• Evidence for the 3 original components of
  Baddeleys model of Working Memory
• Why the original model was revised

2
Clive Wearing
Without our memories, what is left?
Its exactly like death.
3
(No Transcript)
4
History of the STS/LTS distinction
1890 - William James draws distinction between
primary and secondary memory.
SECONDARY MEMORY
PRIMARY MEMORY
Reward portion of present space of time
Genuine past
Unconscious - permanent
Linked to conscious experience
Retrieval is effortless
Retrieval is effortful
The development of computers in the 1960s
provided another analogy which split memory into
two CPU/RAM STS, STORAGE LTS
Modal model of memory developed by Atkinson
Shiffrin (1968)
5
The modal model of memory
But what is the evidence for separate STS / LTS?
6
Evidence for STS / LTS distinction

• Converging evidence appeared to support the STS
  / LTS distinction as proposed by the modal model
  
• Capacity differences - STS limited / LTS
  unlimited
• Encoding differences - STS phonological / LTS
  semantic
• Serial Position Curves - STS Recency / LTS
  Primacy Asymp /
• Forgetting - STS trace decay / LTS
  interference
• NP Evidence - HM intact STS, impaired LTS
• KF intact LTS, impaired STS
• BUT - psychology is never simple...

7
Evidence for STS / LTS distinction

• Encoding differences - How do we comprehend text
  / learn language / remember faces?
• SPCs - Recency effects after 20sec distraction
  following each item (Tzeng, 1973). Long term
  recency (Baddeley Hitch, 1977)
• constant ratio rule (?t / T) (Glenberg et al,
  1980).
• Forgetting - Interference effects in STS (e.g.
  Release from Proactive Interference - RPI)
• NP Evidence - Why is KF able to encode
  information in LTS if the STS is a critical
  bottleneck?
• The modal model provided the first systematic
  attempt to account for the structures and
  processes which comprise the memory system
• But by the end of the 1960s there were several
  well established findings that it was unable to
  account for.

8
Working Memory
Courtney Young was the undisputed Security
Service crossword king. He always claimed it was
too easy to do the Times crossword with a pencil.
He claimed to do it in his head instead. For a
year I watched him do this, until finally I could
resist the temptation no longer. I challenged
him, whereupon he immediately wrote in each
answer, without hesitation. Peter Wright, in
Spy Catcher. (Quote used at beginning of chapter
on Working Memory in Al Parkins text book)
9
Baddeley and Hitchs model of Working Memory
Articulatory loop
10
Background
By late 1960s - STS research laboratory
bound Modal model unable to account for
important data 1. Relationship between type of
encoding and type of store 2. Why STM patients
had normal LTM 3. Dual task data Baddeley and
Hitch - What is the STS for? Assumed to be
used for learning, reasoning and comprehension -
but little or no evidence. Baddeley and Hitch
developed dual task paradigms - Ss perform a
primary task whilst simultaneously performing a
secondary task which is presumed to take up STS
capacity. Overt rehearsal of secondary task
ensures that subjects are not simply switching
between tasks.
11
Dual Task Paradigms
Ss remember (and overtly rehearse) sequences of
0-8 digits
At the same time subjects perform a simple
reasoning task
A precedes B AB (TRUE) B is not preceded by
A AB (FALSE)
Increase in reasoning time is significant, but
not large (35). More importantly No effect on
errors
12
Dual Task Paradigms
Primary task learn a list of words
Secondary tasks 1) copying pairs of
digits 2) rehearsing 3 digit sequence 3)
rehearsing 6 digit sequence
Condition 3 has a small effect on primary task
performance, but it does not effect the recency
component of the SPC.
13
Evidence for the Phonological Loop
Dual task results imply system responsible for
digit span cannot be the same as system
responsible for learning / reasoning. Baddeley
and Hitch (1977) - performance on verbal span
tasks involved a speech-based system.
The phonological loop (AKA articulatory loop)
comprises two components
Articulatory Control Process Based on inner
speech
Auditory Presentation
Visual Presentation
14
Phonological Similarity Effect
Phonological similarity effect
Recall of characters or words is impaired if they
are phonologically similar. (Conrad, 1964
Baddeley, 1966) PVCGE is harder to recall than
XRFYZ This effect can be explained because items
in phonological store are based on phonological
codes. PGCVE all have similar phonological
codes. Similar codes are harder to
discriminate. Hence recall is worse
15
Word Length Effect
Phonological similarity effect
Span for short words is greater than span for
long words.
Is this an effect of syllables or spoken
duration? E.g. is syllable a Unit of storage?
16
Word Length Effect
Spoken duration appears to be crucial Memory
spans are greater for words like Bishop and
Wicket than for Harpoon and Labile
(Baddeley et al, 1975).
Language Articulation Rate Digit
Span Chinese 265ms/digit 9.9 English 321ms/digi
t 6.6 Welsh 385ms/digit 5.8 (Hoosain
Salili, 1988 Ellis Hennelly, 1980)
Memory span and articulation rate are highly
correlated in all age groups - our span increases
as we are able to articulate more rapidly. Overt
or covert articulation serves to maintain items
in the phonological store by refreshing their
fading traces. The faster it can run, the longer
the memory span.
17
Unattended Speech Effect
Performance on span tasks is impaired if items
are accompanied by other verbal material Colle
Welsh (1976) - immediate recall of digits is
impaired if accompanied by sound of someone
reading German. Explanation - unattended
phonological material can gain access to the
phonological store. Salame Baddeley, (1987) -
Spoken digits - one, two impair digit span to
the same degree as similar phonemes like tun,
woo Both impair span more than non-similar
words happy, tipple. Explanation - code is
phonemic, not semantic. This suggests that
listening to music with vocals may impair your
comprehension of complex texts.
18
Patient Data
Learning to read
Modal model cannot explain data from STM patients
such as KF - LTM should also be impaired (STS is
bottleneck) Data can be explained if it is
assumed that these patients have impaired
phonological stores. To what extent does
rehearsal depend on inner speech? Dysarthria
Inability to use speech musculature due to brain
damage. Dysarthric patients have normal digit
spans, and show normal phonological similarity
effects Articulatory control processes do NOT
depend on peripheral speech musculature - we can
run a motor program centrally. SO Phonological
loop preferred to articulatory loop
19
What is the phonological loop for?
1. Learning to read Children with impaired
reading ability have reduced memory spans and
have difficulties in tasks which require the
manipulation of phonological information (e.g.
given Stop, reply Top).
2. Language comprehension STM patients such as
TB have some difficulty in comprehending verbose
or complex sentences e.g. The boys pick the
apples OK The two boys pick the green apples
from the tree Impaired
3. Vocab acquisition There is a strong
correlation between non-word repetition (which
strongly taxes the phonological loop) and
vocabulary size (Gathercole Baddeley, 1989)
20
Imagery
Imagery ignored by the behaviourists, - studied
again in the 1960s.
Imagery debate - Kosslyn and Pylyshyn
Are processes involved in imagery same as those
involved in visual perception?
Imagery Analogue or Propositional ?
Debate proved rather barren - but generated
interesting phenomena.
Neuropsychological and neuroimaging data suggests
neural substrates involved in vision also
involved in imagery.
21
The visuospatial sketch-pad
Baddeley - listening to American football
disrupts driving
VSSP - A workspace in which an image can be
stored and manipulated to guide behaviour.
Brooks Matrix Task (1967) Subjects learn sequence
of sentences Spatial In the next square to the
right put a 2 Non-spatial In the next square
to the quick put a 21
Subjects remembered 8 spatial vs 6
non-spatial. Spatial instructions better when
presented auditorily Non-spatial instructions
better when presented visually
22
The visuospatial sketch-pad
Baddeley et al, 1975 - Ss perform Brooks matrix
task with and without concurrent distractor -
pursuit rotor.
Tracking disrupts the spatial task, but not its
verbal equivalent Sketchpad relies on spatial
coding
23
What is the sketchpad for?
Not as well studied as the articulatory loop
Geographical orientation - learning our way
around our environment.
Planning and performing spatial tasks
Hatano Osawa (1983) -Japanese abacus experts
memory for numbers is disrupted by concurrent
spatial but not verbal task.
24
What is the sketchpad for?
(Eye Movement Desensitisation Reprocessing) From
the website What is EMDR an innovative method
of psychotherapyThe focus of EMDR treatment is
the resolution of emotional distress arising from
difficult childhood experiences, or the recovery
from the effects of critical incidents, such as
automobile accidents, assault, natural disasters,
and combat trauma PTSD. Other problems treated
with EMDR are phobias, panic attacks, distress in
children, and substance abuse. Another innovative
focus of EMDR is performance enhancement which
aims to improve the functioning of people at
work, in sports, and in performing arts
25
EMDR
EMDR is a Therapy used by Psychotherapists,
Psychiatrists, Clinical Psychologists etc
primarily for the treatment of PTSD. Involves
following the finger of therapist whilst
imagining negative information identified with
problem From the website HOW DOES EMDR
WORK? It is not clear how EMDR works because
neuroscience researchers are still exploring how
the brain works... However, there is evidence for
an innate information processing system that
exists as part of human thinking
processes. EMDR appears to produce a direct
effect on the way the brain processes upsetting
material. Researchers have suggested that the eye
movements trigger a neurophysiological mechanism
that activates an "accelerated information
processing system." Accelerated information
processing is a phrase used in EMDR to describe
the rapid working through, metabolizing, of
upsetting experiences. Stickgold R (2002) EMDR
A putative neurobiological mechanism of action
JOURNAL OF CLINICAL PSYCHOLOGY 58 (1) 61-75
EMDR induces a neurobiological state, similar
to that of REM sleep, which is optimally
configured to support the cortical integration of
traumatic memories into general semantic
networks. We suggest that this integration can
then lead to a reduction in the strength of
hippocampally mediated episodic memories of the
traumatic event as well as the memories'
associated, amygdala-dependent, negative affect.
26
EMDR
Experimental Psychology to the rescue McNally RJ
(1999) EMDR and mesmerism A comparative
historical analysis J ANXIETY DISORD 13 (1-2)
225-236 JAN-APR 1999 Most disabling symptom of
PTSD is recurring, intrusive images of
precipitating trauma. These images are
presumably instantiated in VSSP Effective
volitional eye tracking involves the storage and
manipulation of both visual and spatial
information IN OTHER WORDS IT COMPETES FOR VSSP
RESOURCES Therefore EMDR is simply another
desensitisation procedure - of the type
traditionally used by behavioural
therapists. BUT Christman SD, Propper RE, Dion
A. (2004) Increased interhemispheric interaction
is associated with decreased false memories in a
verbal converging semantic associates paradigm.
Brain Cogn. 56313-9.
27
The Central Executive
Most complex and least understood component of WM
model
In some ways the central executive functions
more like an attentional system than a memory
store - Baddeley
Model suggests CE coordinates the activity of the
two slave systems
Other potential roles for the CE include
coordinating retrieval strategies, and selective
attention
Baddeley suggests that a model of action control
developed by Norman and Shallice (1980,1986) may
serve as a model of the central executive
28
Norman and Shallices (1986) model of attentional
control
29
Evidence for the CE
Dual task performance and DAT
Pursuit rotor and digit span tasks were adjusted
so that individual performance was identical in
DAT and matched controls
Combining the two tasks caused greater costs in
the DAT patients than the controls - CE impaired
in DAT
Random number generation
Ss required to generate random sequences of
letters make more repetitions and stereotyped
responses the faster the task
Dominant schema (ABC, ITV etc) must be constantly
inhibited by the SAS and novel schema activated.
30
Evidence for the CE
Neuropsychological evidence - dysexcutive
syndrome
Original Norman and Shallice model developed to
account for behaviour of patients with frontal
lobe lesions.
Perseveration - patients have lost ability to
interrupt ongoing schemas
Catatonia - patients can remain motionless and
speechless for hours - unable to initate schemas.
Distractibility - schemas easily captured by
external/internal stimuli
Utilisation behaviour - Lhermite (1983)
31
Utilisation Behaviour
Utilisation behaviour The tendency to grasp
common objects when presented, and perform the
function commonly associated with the object E.g
Lhermite (1983)
32
Problems for original WM model
1. Articulatory suppression According to the
model, AS should prevent registration of visual
material (which must be recoded
phonologically) In fact, span only drops
slightly (Baddeley et al, 1994) 2.
Neuropsychological data STM patients, with
digit spans of 2 or less, have visual spans of
about 4 (Baddeley et al, 1997). 3. Chunking If
stimuli comprise a meaningful sentence, span is
considerably increased (e.g. info in LTM is used
to chunk)
33
Problems for original WM model
4. Rehearsal Not all rehearsal can be subvocal
How are items in VSS rehearsed? What about
children? 5. The role of consciousness CE
originally proposed to assist in binding - our
ability to integrate information about location,
colour, size, smell, feel etc of objects. How
could it do this without a multimodal short term
store? Baddeley (2000) suggests the above
problems can be solved by an Episodic Buffer.
34
A Revised WM Model
Central Executive
35
The Episodic Buffer

• A limited capacity temporary storage system that
  is capable of integrating information from a
  variety of sources
• Controlled by the CE
• Feeds information into and retrieves information
  from LTS
• Uses a common multidimensional code
• The Episodic Buffer makes the link between
  Working Memory and LTM more explicit
• BUT
• Are VSS and AL still necessary?

36
Summary

• Original model was able to account for a
  considerable body of data that the modal concept
  of an STS could not explain.
• The concept of WM has proven to be enormously
  influential, and is used by Neuroscientists,
  Neuropsychologists, and AI researchers.
• Problems with the original model led to the
  addition of the Episodic Buffer
• The central executive component remains
  under-specified, and controversial.