psyco 350 lec #4 – slide 1 lecture 4 – psyco 350, a1 winter, 2011 n. r. brown

Psyco 350 Lec #4 – Slide 1

Lecture 4 – Psyco 350, A1Winter, 2011

N. R. Brown


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


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


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.


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


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


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


Studying Retrieval from STM


The Sternberg TaskA Cognitive Psychology Classic

Research Style:

• Paradigm-driven

• Exhaustive exploration of “parameter space”

• Disregard for:– intrinsic importance of phenomena

– individual/cultural differences

– emotion & motivation

Slide 9

Psyco 350 Lec #4– Slide 10

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””

Slide 10


STM Retrieval: 3 Possibilities

• Issue: – How do we access

information in STM?

– Is Item X in STM?

• Three possibilities:– Parallel –

simultaneous access to all items.

– Serial – consider 1 item at a time.

Retrieval Models

Parallel Serial

ExhaustiveSelf- Terminating


STM Retrieval: 3 Possibilities

Three possibilities:• Parallel – simulators

access to all items.• Serial – consider 1

item at a time.– Self-terminating

• Stop when:

target = content

– Exhaustive• Check each item on

list

Retrieval Models

Parallel Serial

ExhaustiveSelf- Terminating


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)


Sternberg Task: Method


Competing Retrieval Model Predictions


Why Serial Models Make Different PredictionsAdditive Factors Logic (Radvansky, pp. 58-60)


Sternberg Task: Results

• RT w/ set size

Implication: serial

• Negative = PositiveImplication: exhaustive


Sternberg’s Model


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


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


Sternberg Task: Results

• RT w/ set size

Implication: serial

• Negative = PositiveImplication: exhaustive


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


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


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.


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


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.


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


Grammatical Reasoning Task

Design:• memory load

– 0 to 8 digits

• sentence type– true value X voice X

affirmation


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


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


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 multi-component WM model.


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


Basic WM Model


Current WM Model


Dual Task Reasoning: Results

• No effect on reasoning when load is light (0-2)

• reason slowed by load• error rate low regardless

of load.


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.


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


The Phonological Loop

Phonological Store

Phonological Store: holds small amount of speech based information

Articulatory Control Process: Based on inner speech

Auditory Presentation

VisualPresentation


Phonological Loop

• Speech-based System: – phonological similarity – irrelevant speech – articulartory suppression

• 2-s Capacity:– word length effect

– cross-linguistic Δ’s

– developmental Δ’s


Evidence for the Phonological Loop


Evidence for Phonological Loop

• Phonological Similarity Effectsimilar sounding list < dissimilar sounding lists

------- vs ---------

• (Almost) No Evidence for Semantic Similarity Effect

• Implies: representation is speech-based not meaning based.



• Irrelevant Speech Effect– Recall impaired if items are accompanied by other

verbal material.

– Effect found w/: same-language words, same-language non-words, foreign words.

• Interpretation: “unattended (linguistic) material was gaining access to

the phonological store.”

-- Baddeley, p. 53



• 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


Evidence for the 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


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



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.



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.


Cross-Linguistic Δs in Digit SpanNaveh-Benjamin & Ayers (1986)

As predicted:• span larger

for languages w/ short digits than long

• span ≈ 2 X reading rate


Age-related Δs Digit SpanHulme (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


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)


VSSP

• Function:– “construction, maintained, & manipulation of

mental images.” – Radvansky, p. 97

• Assumptions:– Independence of VSSP & Phonological Loop


Visuo-spatial sketchpad

Operations:

• Mental rotation

• Mental scanning

• Boundary extension

• Dynamic memory

Supports:

Spatial problem-solving (moving a couch)

Prediction of dynamic consequences.


Independence of VSSP & Phonological LoopBrooks (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


Independence of VSSP & Phonological LoopBrooks (1968)

• Design (2X3)

TASK X RESPONSE MODE

image scanning pointing

grammatical decision tapping

vocal


Brooks (1968): Image Scanning Task

Given a block letter & starting point:

If current corner is top or bottom “yes”

Otherwise ”no”


Brooks (1968): Image Scanning Task

Given a proverb/cliché:

If current word is noun “yes”

Otherwise ”no”

Example:


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


Brooks (1968): Pointing


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

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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 1 lecture 4 – psyco 350, a1 winter, 2011 n. r. brown

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