Lecture 4 – Psyco 350, A1
Winter, 2011
N. R. Brown
Psyco 350 Lec #4 – Slide 1
Outline
• Aspects of Modal Model:
• Duration/Forgetting: Brown-Peterson Task
• Retrieval: Sternberg Task
• Problems w/ Modal Model
• Dual Task Experiment
• Baddeley’s Model of Working Memory
– Phonological Loop
– Visuo-spatial sketchpad
– Central Executive
Psyco 350 Lec #4 – Slide 2
Duration & Forgetting in STM
• Brown-Peterson Task:
Initial attempt to measure duration of STM
• Procedure:
– hear sub-span target set: 3 letters
– count backwards for X s
– recall target
• Manipulation – length of retention interval
• Assumption:
– Counting task knocks out rehearsal
– Measure of the rate of forgetting
Psyco 350 Lec #4 – Slide 3
Brown-Peterson: Main Finding
• In the absence of
rehearsal, sub-span
material is forgotten very
rapidly from STM
• Initial interpretation:
information rapidly
decays from STM
• Note: w/ 0-delay, only
80% accuracy.
Psyco 350 Lec #4 – Slide 4
A Test of Decay Hypothesis
• Waugh & Norman (1965) -- Serial Probe Task
• Method:
– auditory, 16 digit list, followed by probe digit
– TASK: name the digit that followed the probe
• Manipulation:
– location of probed item
– Presentation time: 1digit/s vs 4 digits/s
• Decay prediction:
– recall: 1 digit/s < 4 digits/s
• Interference prediction:
– recall: 1 digit/s ≈4 digits/s
Psyco 350 Lec #3 – Slide 5
Waugh & Norman (1965)
Results:
• Recall  w/ # of
intervening items
– consistent w/ both
decay & interference
• Recall (more or less)
unaffected by
presentation rate
– Consistent only w/
interference
Psyco 350 Lec #4 – Slide 6
Evidence for PI in Brown-Peterson Task
• Keppel & Underwood
(1962)
• Competing Predictions:
– Decay prediction: Does
delay affect recall? NO
– Interference prediction:
Performance decline
across trials? YES
• Conclusion:
– Interference causes
forgetting in STM
Psyco 350 Lec #4 – Slide 7
Studying Retrieval from STM
Psyco 350 Lec #4 – Slide 8
The Sternberg Task
A Cognitive Psychology Classic
Research Style:
• Paradigm-driven
• Exhaustive exploration of “parameter space”
• Disregard for:
– intrinsic importance of phenomena
– individual/cultural differences
– emotion & motivation
Psyco 350 Lec #4 – Slide 9
Slide 9
An Example: The Sternberg Task
An Information Processing Classic:
• 2,500+ cites for two 1969 papers
Task:
Target set: short list of items
Probe: a single item
Target present  “Old”
Target absent  “New””
Psyco 350 Lec #4– Slide 10
Slide 10
STM Retrieval: 3 Possibilities
• Issue:
Retrieval
Models
Parallel
SelfTerminating
Psyco 350 Lec #4 – Slide 11
– How do we access
information in STM?
– Is Item X in STM?
Serial
Exhaustive
• Three possibilities:
– Parallel –
simultaneous access
to all items.
– Serial – consider 1
item at a time.
STM Retrieval: 3 Possibilities
Retrieval
Models
Parallel
Serial
Three possibilities:
• Parallel – simulators
access to all items.
• Serial – consider 1
item at a time.
– Self-terminating
• Stop when:
target = content
SelfTerminating
Exhaustive
– Exhaustive
• Check each item on
list
Psyco 350 Lec #4 – Slide 12
Selecting between Retrieval Model:
The Sternberg Task
• Task
– Materials:
• Memory Set: N letters
• Probe: target letter
– Question: Is probe in memory set?
• Manipulations
– Set Size: 1 to 6 letters
– Probe Type:
• positive (in memory set)
• negative (not it set)
Psyco 350 Lec #4 – Slide 13
Sternberg Task: Method
Psyco 350 Lec #4– Slide 14
Competing Retrieval Model Predictions
Psyco 350 Lec #4 – Slide 15
Why Serial Models Make Different Predictions
Additive Factors Logic (Radvansky, pp. 58-60)
Psyco 350 Lec #4 – Slide 16
Sternberg Task: Results
• RT  w/ set size
Implication: serial
• Negative = Positive
Implication: exhaustive
Psyco 350 Lec #4– Slide 17
Sternberg’s Model
Psyco 350 Lec #4 – Slide 18
Problems / Serial Exhaustive Process
•
Conceptual:
– 40 ms/comparison seems awfully fast.
•
Empirical:
– Repetition Effect (Baddeley & Ecob, 1973):
Probe = T: RTWTN < RTWGN
– Serial Position Effects (Corballis et al., 1972)
Probe = T: TRWGN < RTWGN
Psyco 350 Lec #4– Slide 19
Alternative Approach to Sternberg Findings
Assumptions:
• memory set, the most active portion of LTM
• memory “searched” in parallel
• decision process:
– “Yes”: probe-memory similarity > threshold
– “No”: at deadline – similarity < threshold
Set Size Effects:
• encoding: activation/item  as set size 
• retrieval: speed of assessment  as set size 
Psyco 350 Lec #4– Slide 20
Sternberg Task: Results
• RT  w/ set size
Implication: serial
• Negative = Positive
Implication: exhaustive
Psyco 350 Lec #4 – Slide 21
Problems / Serial Exhaustive Process
•
Conceptual:
– 40 ms/comparison seems awfully fast.
•
Empirical:
– Repetition Effect (Baddeley & Ecob, 1973):
Probe = T: RTWTN < RTWGN
– Serial Position Effects (Corballis et al., 1972)
Probe = T: TRWGN < RTWGN
Psyco 350 Lec #4 – Slide 22
Alternative Approach to Sternberg Findings
Assumptions:
• memory set, the most active portion of LTM
• memory “searched” in parallel
• decision process:
– “Yes”: probe-memory similarity > threshold
– “No”: at deadline – similarity < threshold
Set Size Effects:
• encoding: activation/item  as set size 
• retrieval: speed of assessment  as set size 
Psyco 350 Lec #4 – Slide 23
STM, But …
Model Modal accounts for serial position curve, but …
not long-term recency effects.
Capacity of STM is limited, but …
also affected by chunking & expertise.
In the absence of rehearsal, information is forgotten rapidly,
but …
not on the first trial.
Serial exhaustive process may be used to scan STM, or…
a parallel process may be used to assess the active
contents of LTM.
Simple “slot model” can’t account for performance of classic
STM task.
Psyco 350 Lec #4 – Slide 24
Dual-task Performance & the Demise of STM
• STM In Modal Model
– single component short-term store
– functions
• temporary storage – lists, task relevant info
• transfer to LTM via rehearsal
“A [single] system for holding and manipulating
information for a wide variety of tasks such as
learning, comprehension, and reasoning”
-- Baddeley, p. 67
Psyco 350 Lec #4 – Slide 25
Dual-task Performance & the Demise of STM
A Dual Task.
1. encode list of digits
2. perform a cognitive task (e.g., reasoning,
comprehension)
3. recall list of digits.
If both load and task make use of same store, then
increasing load (to span) should disrupt performance
on cog task.
Psyco 350 Lec #4 – Slide 26
Grammatical Reason W/ Memory Load
(Baddeley, 1986)
• Concurrent Tasks
– Memory span task – provides a memory load
– Grammatical reasoning task
• Procedure:
– auditor presentation of digit load – 1 digit/s
– concurrent overt rehearsal of load
– visual presentation of letter pair & sentence
– respond T/F to sentence
– serial recall of digits
Psyco 350 Lec #4 – Slide 27
Grammatical Reasoning Task
Design:
• memory load
– 0 to 8 digits
• sentence type
– true value X voice X
affirmation
Psyco 350 Lec #4 – Slide 28
Implications of Single-store View
• Assumptions:
– Span Task – absorbs (almost) all STM capacity
– Reasoning task – requires access to STM
Prediction:
If span task absorbs all of STM 
dual task requirements should produce a dramatic
impairment in performance.
Span-length memory load  catastrophic
interference
Psyco 350 Lec #4 – Slide 29
Dual Task Reasoning: Results
• No effect on reasoning
when load is light (0-2)
• reason slowed by load
• error rate low regardless
of load.
----------------------------------Load also has negative,
but non-catastrophic,
impact on free recall &
text comprehension
Psyco 350 Lec #4 – Slide 30
Implication of Dual Task Performance
• System responsible for digit span cannot be
the same as system responsible for learning /
reasoning.
• Motivated the development of the multicomponent WM model.
Psyco 350 Lec #4 – Slide 31
Working Memory: An Alterative to STM
• Baddeley and Hitch’s (1983) model
• Central executive
– Control center of working memory
• Two slave systems:
– Phonological loop
• Processes verbal/acoustic information
– Visuo-spatial sketch pad
• Processes visual and spatial information
Psyco 350 Lec #4 – Slide 32
Basic WM Model
Psyco 350 Lec #4 – Slide 33
Psyco 350 Lec #4 – Slide 34
Current WM Model
Psyco 350 Lec #4 – Slide 35
Dual Task Reasoning: Results
• No effect on reasoning
when load is light (0-2)
• reason slowed by load
• error rate low regardless
of load.
Psyco 350 Lec #4 – Slide 36
WM Interpretation of Dual Task
• Load maintenance requires:
– access to phonological store
– minor attentional resources to schedule rehearsal
• Grammatical reasoning requires:
– attentional resources for sentence
understanding/reasoning
– limited access to phonological store – note: sentences
presented visually
As load , attentional demands . Thus, less
capacity available for sentence processing.
Psyco 350 Lec #4 – Slide 37
Phonological loop
Two components
• Phonological short-term store
– Phonological information that decays with time
• Inner ear
• Subvocal rehearsal process
– Articulatory-like rehearsal that needs active
maintenance
• Inner voice
Psyco 350 Lec #4 – Slide 38
The Phonological Loop
Phonological Store: holds small amount of
speech based information
Articulatory Control
Process: Based on inner
speech
Phonological
Store
Visual
Presentation
Psyco 350 Lec #4 – Slide 39
Auditory
Presentation
Phonological Loop
• Speech-based System:
– phonological similarity 
– irrelevant speech

– articulartory suppression 
• 2-s Capacity:
– word length effect
– cross-linguistic Δ’s
– developmental Δ’s
Psyco 350 Lec #4 – Slide 40
Evidence for the Phonological Loop
Psyco 350 Lec #4 – Slide 41
Evidence for Phonological Loop
• Phonological Similarity Effect
similar sounding list < dissimilar sounding lists
------vs
---------
• (Almost) No Evidence for Semantic Similarity
Effect
• Implies: representation is speech-based not
meaning based.
Psyco 350 Lec #4 – Slide 42
Evidence for Phonological Loop
• Irrelevant Speech Effect
– Recall impaired if items are accompanied by other
verbal material.
– Effect found w/: same-language words, samelanguage non-words, foreign words.
• Interpretation:
“unattended (linguistic) material was gaining access to
the phonological store.”
-- Baddeley, p. 53
Psyco 350 Lec #4 – Slide 43
Evidence for Phonological Loop
• Articulartory Suppression
– concurrent (overt or covert) articulation, decreases
word span.
(“the, the, the…” ; “one, two, three, one, two..)
– concurrent articulation decreases
• the phonological similarity effect
• word length effect.
• Interpretation:
articulation of irrelevant items dominates ACP - Words
cannot be “rehearsed” or recoded into phonological
code
Psyco 350 Lec #4 – Slide 44
Evidence for the Phonological Loop
Psyco 350 Lec #4 – Slide 45
Evidence for Phonological Loop
• Word Length Effect
word span decrease as # of syllables/word
increases.
• Recall depends of reading rate.
– # words recalled ≈ 2 * (reading rate)
• reading rate = # words read / s
Psyco 350 Lec #4 – Slide 46
Phonological Loop – Capacity of Phono Store
Baddeley et al (1975)
Task: serial recall
Materials:5-word lists
Manipulation: syllable
length
Results:
• recall , as syllable
length 
• recall predicted by
reading rate.
• cf. STM predictions
Psyco 350 Lec #4 – Slide 47
Phonological Loop – Capacity of Phono Store
Baddeley et at (1975)
• linear relation between
reading time & recall
• Interpretation:
– capacity of phono loop
~ 2 s of speech materials
• Reason
– fast fading phono trace
– rehearsal refreshes trace.
– if not rehearsed within 2
s, most info lost.
Psyco 350 Lec #4 – Slide 48
Phonological Loop – Capacity of Phono Store
Baddeley et at (1975)
• Implications:
– across languages, digit
span should be related
to mean syllable length
of digits.
– digit span should
increase w/ age,
because speech rate
does.
Psyco 350 Lec #4 – Slide 49
Cross-Linguistic Δs in Digit Span
Naveh-Benjamin & Ayers (1986)
As predicted:
• span larger
for languages
w/ short digits
than long
• span ≈ 2 X
reading rate
Psyco 350 Lec #4 – Slide 50
Age-related Δs Digit Span
Hulme (1984)
As predicted:
• span  w/ age
• span ≈ 2 X speech
rate
----------------------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
Psyco 350 Lec #4 – Slide 51
Phonological Loops: Functions
•
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).
•
Language comprehension:
STM patients 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
•
Vocabulary acquisition
There is a strong correlation between non-word repetition
(which strongly taxes the phonological loop) and vocabulary
size (Gathercole & Baddeley, 1989)
Psyco 350 Lec #4 – Slide 52
Psyco 350 Lec #4 – Slide 53
VSSP
• Function:
– “construction, maintained, & manipulation of
mental images.”
– Radvansky, p. 97
• Assumptions:
– Independence of VSSP & Phonological Loop
Psyco 350 Lec #4 – Slide 54
Visuo-spatial sketchpad
Operations:
• Mental rotation
• Mental scanning
• Boundary extension
• Dynamic memory
Supports:
Spatial problem-solving (moving a couch)
Prediction of dynamic consequences.
Psyco 350 Lec #4 – Slide 55
Independence of VSSP & Phonological Loop
Brooks (1968)
• Dual Task Experiment
– Goal to demonstrate:
• spatial response mode interference w/ spatial
processing
• verbal response mode interferes w/ verbal
processing
• cross-modal tasks produce little interference
Psyco 350 Lec #4 – Slide 56
Independence of VSSP & Phonological Loop
Brooks (1968)
• Design (2X3)
TASK
X
image scanning
grammatical decision
Psyco 350 Lec #4 – Slide 57
RESPONSE MODE
pointing
tapping
vocal
Brooks (1968): Image Scanning Task
Given a block letter & starting point:
If current corner is top or bottom “yes”
Otherwise
”no”
Psyco 350 Lec #4 – Slide 58
Brooks (1968): Image Scanning Task
Given a proverb/cliché:
If current word is noun “yes”
Otherwise
”no”
Example:
Psyco 350 Lec #4 – Slide 59
Brooks (1968): Response Modes
While performing target task:
• Vocal – say “yes”/”no”
• Taping – left tap = “yes”; right tap = “no”
• Pointing – point to successive “y”/”n” pairs on
response sheet
Psyco 350 Lec #4 – Slide 60
Brooks (1968): Pointing
Psyco 350 Lec #4 – Slide 61
Brooks (1968): Results
>>
≈
• Spatial response mode:
– interfered w/ spatial task
– did not interfere w/ verbal task
• Verbal response mode:
– interfered w/ verbal task
– did not interfere w/ spatial task
Psyco 350 Lec #4 – Slide 62
≈
<<
Brooks (1968): Interpretation
• Task X Mode interaction indicates:
– separate & limited pool of resources for verbal
& spatial task
• image scanning task & spatial response mode
draw on the limited resources of the VSSP.
• grammatical decision task & vocal response
mode both draw on the resources of the
phonological loop.
Psyco 350 Lec #4 – Slide 63