MULTI STORE
MODEL OF
MEMORY
By Atkinson & Shriffin
By Abarajitha Kuruvayooran
What is the multi store model of memory???
Memory is not a single system — it is a series of separate stores through which
information flows in a fixed sequence.
The three stores are:
Sensory Register
(SR)
Short-Term
Memory (STM)
very brief holding of raw
sensory input
Environment
→ conscious, working memory
SR
Long-Term
Memory (LTM)
permanent, unlimited storage
The flow:
STM
(if attended to)
LTM
(if rehearsed)
THE THREE STORES
Store
Duration
Capacity
Encoding
Sensory
Register
Very brief — 0.25–
0.5 sec (iconic) / 3–
4 sec (echoic)
Very large — all
sensory input
Modality-specific
(visual, auditory, etc.)
Short-Term
Memory
15–30 seconds
without rehearsal
7 ± 2 chunks (Miller,
1956)
Primarily acoustic
(sound-based)
Unlimited
Primarily semantic
(meaning-based)
Long-Term
Memory
Potentially lifetime
THE SENSORY REGISTER
First store — holds a brief impression of everything your senses detect.
Most of it decays immediately through trace decay.
Only information that receives selective attention is passed to STM.
Two main types:Iconic store — visual information (≈ 0.25–0.5 sec) — Sperling (1960) and
Echoic store — auditory information (≈ 3–4 sec)
Sperling (1960): showed that the SR holds far more than STM — whole rows of letters
available briefly, but most decay before they can be transferred
THE SHORT-TERM MEMORY
Duration: 15–30 seconds without maintenance rehearsal (Peterson & Peterson, 1959 —
trigram study)
Capacity: 7 ± 2 items (Miller, 1956) — can be expanded through chunking
Encoding: primarily acoustic — we tend to store STM items by how they sound.
Evidence: Conrad (1964) — participants confused acoustically similar letters (B, D, P, T) in
STM even when presented visually.
Maintenance rehearsal keeps information in STM and eventually transfers it to LTM.
Without rehearsal → displacement or decay.
long-term memory
Duration: potentially a lifetime — some memories last decades
Capacity: unlimited — no known upper limit
Encoding: primarily semantic — stored by meaning
Evidence: Baddeley (1966) — participants had more difficulty recalling semantically
similar words from LTM (e.g. big, large, great) than acoustically similar ones.
Retrieval — information can be brought back into STM (working memory) when needed.
Forgetting from LTM: retrieval failure (cue-dependent forgetting) rather than decay.
THE SERIAL POSITION EFFECT
Murdock (1962)
When participants are given a list of words to
recall in any order (free recall), a consistent
pattern emerges:
Primacy effect — words at the beginning of
the list are recalled well
Because they had more time in STM →
more rehearsal → transferred to LTM
Recency effect — words at the end of the list
are recalled best
Because they are still in STM at the time
of recall (not yet displaced)
Words in the middle are recalled worst —
they entered STM when it was already
occupied, and were displaced before
reaching LTM
What this tells us:
Primacy → supports the existence of LTM
(rehearsal and transfer)
Recency → supports the existence of STM
(recent items still 'live' there)
The two effects together are strong
evidence for two separate stores — a core
claim of the MSM
Disruption evidence:
If a distracting task is given immediately
after the list (counting backwards) — the
recency effect disappears but the primacy
effect remains → confirms recency relies on
STM, which is disrupted
THE DUAL TASK EXPERIMENT
Baddeley & Hitch (1976) — Supporting & Challenging MSM
The Purpose: If STM is a single, fixed-capacity store (as MSM claims), doing two tasks that both require
STM simultaneously should be impossible — they would compete for the same resource.
Method: Participants were given:
A digit span task (holding a string of numbers in STM) — AND simultaneously —
A reasoning task or reading task requiring STM
Findings:
Participants could do BOTH tasks at the same time — with only a slight drop in performance
Performance did not collapse, even when STM should have been full
Conclusion:
STM is NOT a single unitary store — it is more complex than MSM proposes
This led Baddeley & Hitch to develop the Working Memory Model (1974) as a replacement — STM has
multiple sub-systems (phonological loop, visuospatial sketchpad, central executive)
The dual task experiment is therefore both a test of MSM and evidence that challenges it
EVALUATION OF MSM
Strengths
1. Strong research support
Peterson & Peterson (1959): demonstrated limited STM duration (trigrams forgotten in ~18 sec with
rehearsal prevented)
Miller (1956): 7 ± 2 capacity of STM is robustly replicated
Baddeley (1966): different encoding in STM (acoustic) vs LTM (semantic) — directly supports distinct
stores
2. Serial position effect (Murdock, 1962)
Primacy and recency effects together provide elegant evidence for two separate stores — hard to explain
with a single-store model
3. Case study support — HM (Scoville & Milner, 1957)
Patient HM had his hippocampus removed — permanently unable to form new LTM but STM remained
intact
Biological evidence for two anatomically separate memory systems
4. Scientific credibility
Highly testable, falsifiable, produced decades of productive experimental research.
EVALUATION OF MSM CONTD
Limitations
1. Over-simplified — STM is not a single store
Baddeley & Hitch's dual task experiment showed STM has multiple components
Working Memory Model (1974) replaced MSM's unitary STM with a more accurate multi-component model.
2. Rehearsal is not the only route to LTM
MSM claims maintenance rehearsal is the mechanism for transfer to LTM
Craik & Lockhart (1972) — Levels of Processing: deeply processed material enters LTM without deliberate
rehearsal (e.g. emotionally significant events remembered without repetition).
3. LTM is not a single store
Tulving (1985) — LTM consists of distinct types: episodic (personal events), semantic (facts), procedural
(skills).
MSM treats LTM as one homogeneous store — this is inaccurate.
4. Case study evidence is unreliable
HM and similar patients are unique individuals — results may not generalise
Brain damage varies — difficult to draw universal conclusions about normal memory
ISSUES AND DEBATES
Reductionism
MSM reduces the complexity of
memory to a linear flow through
three stores with fixed properties
It treats memory as an informationprocessing machine — ignores
emotional, social and contextual
factors that influence memory
Biological reductionism:
neuroimaging studies show memory
is distributed across brain networks
— not three neatly separate stores
Counter-argument: reductionism is
not necessarily wrong — it has
scientific utility and produced
testable predictions
Ethical Issues
Laboratory research on memory (Peterson & Peterson,
Conrad, Baddeley) — participants given tasks and
sometimes deceived about the purpose → raises informed
consent concerns.
Use of brain-damaged patients (HM, Clive Wearing): these
individuals could not fully consent; their cases were used
extensively in research and sometimes in media — raises
issues of privacy, dignity, and exploitation of vulnerability.
HM specifically: his identity (Henry Molaison) was only
revealed after his death in 2008 — was kept anonymous
during his lifetime, which was a form of protection but also
raises questions about who owns someone's medical
narrative.
Application to education and policy — if memory is
understood as a fixed-capacity system, this could unjustly
label individuals as having 'poor STM' without considering
neurodiversity, anxiety or other factors.
ISSUES AND DEBATES contd
Psychology as Science
Nature vs Nurture
MSM focuses on the structure of
memory (nature) — assumes fixed
capacity and duration.
Ignores how environment and
experience (nurture) shape
memory — e.g. chunking ability
improves with expertise; cultural
practices affect encoding
strategies.
MSM is highly scientific —
controlled lab experiments,
operationalised variables,
replicable findings.
Strength: it made memory
research empirically rigorous.
Limitation: lab tasks (nonsense
syllables, digit spans) lack
ecological validity — they don't
reflect how memory works in real
life.
THANK
YOU