psyco 350 lec #3 – slide 1 lecture 3 – psyco 350, a1 winter, 2011 n. r. brown

Psyco 350 Lec #3 – Slide 1

Lecture 3 – Psyco 350, A1Winter, 2011

N. R. Brown


Outline

• Aspects of Modal Model: – STM vs LTM: Serial Position Curve

– Properties of STM• Capacity: Span Task• Duration/Forgetting: Brown-Peterson Task• Retrieval: Sternberg Task

• Problems w/ Modal Model


Modal Model: Evidence STM – LTM Distinction

• Assumption: – dual stores – STM & LTM:

• small amount of info held briefly in STM• rehearsal enables and is required for transfer

from STM to LTM

• Support: serial-position-curve phenomena


Free Recall & the Serial Position Curve

Memory Tests

Recognition

Uncued

Serial

Cued

Recall

FREE


Free Recall Task


Free Recall Task

List #1 – 15 words

Instructions:

There are 15 words on this list.

When I say to, please write down as many of these words as you can.


Free Recall Task

List #2 – 15 words; 20 s delay

Instructions:

There are 15 words on this list.

When I say to, please write down as many of these words as you can.


In-Class Serial Position Curve

0102030405060708090

100

1 3 5 7 9 11 13 15

Serial Position

% R

ecal

led

NoDelay

20 s Delay



• Free recall:– uncued recall of studied items

– order of output unconstrained

• Manipulate a variety of:– Encoding factors (e.g. presentation rate)

– Storage factors (e.g., delay)

• Dependent variable:– % recalled as a function of serial position


Serial Position Curve

• Primacy: Good recall for 1st few items • Recency: Good recall for last few items on list


Modal Account of the Serial Position Curve

• Recency Effect produced by read-out from STM

• Primacy & “pre-recency” reflect information retrieved from LTM

• “Transfer” from STM to LTM caused by rehearsal.

• Implications: – Primacy & Prerecency: w/ rehearsal

– Recency: unaffected by rehearsal


Rundus (1971): Rehearsal & the Serial Position Curve

• Materials– 20-word list

– presentation rate: 5 s/word

• Task(s): – During study – overt rehearsal

– During test – free recall


Rundus: Rehersal Protocols


Relation between Rehearsal & Recall

• Analysis:– # rehearsals for each

word (position)

– % recall for each word (position)

• Results:– “For a given amount of

rehearsal, items from the initial serial positions are no better recalled than items from the middle of the list” – Rundus, 1971, p. 66


Relation between Study-time (Rehearsal) & Recall

• Glanzer & Cunitz (1966)

• manipulate study-time.

• Assume: study time & rehearsal related

• Results:– Primacy & Prerecency:

w/ study time

– Recency: unaffected by rehearsal

styd


Relation between Filled Delay & Recall

• Glanzer & Cunitz (1966)

• Manipulate retention interval.

• Assume filled delay replaces contents of STM

• Results:– Primacy & Prerecency:

un affected by delay

– Recency as delay

styd


Amnesia & Serial Position• Baddeley & Warrington

(1970)• H.M. – removal temporal

lobe and hippocampus• Clobbered Explicit

memory.• Yet – on immediate test,

recency intact

styd


Dissociation: Evidence for Dual Store• Dissociation – when “a single variable has different affects on

two or more measures.”• Evidence for separate stores, processes, or representation.• Many variables have dissociative effect on the prerecency &

recency portion of serial position curve.

Prerecency Recency

Study time =

Post-list distraction = Ant. Amnesia =

List Length =

Word Frequency


Measuring STM Capacity: Memory Span Task

• Instructions: Recall the digits in the order presented.



Memory Tests

Recognition

Uncued

Serial

Cued

Recall

FREE


Measuring STM Capacity: Digit-Span Task

Span Test:

• Materials – random digits, words, etc

• Task – serial recall

• Span Defined – list length that produces accurate performance on 50% of trials


Capacity: Span Task

• Digit Span Defined: # of digits accurately recalled 50% of the time

• Standard Span: 7±2 digits

• Modal Model Interpretation (Miller, 1956):

– STM Capacity: ≈ 7 “chunks”


Modal Model w/ 7 Slots – 1 chunk/slot


Chunking

• Chunking – “the process of combining information so that it takes up as little as possible of the limited space in STM”

– Klatzky, p. 74• Chunking span

• Why not a limitless STM?– “Chunk chunked chunks?

• Required:– Chunking scheme– Time to apply scheme


Extraordinary Digit-Span: SF

• Materials:– random digits

– auditory presentation

– 1 digit/s

• Results:– After 45 days of practice: span = 83


SF: Digit Span


How did he do it?

1. Chunk (and elaborated) groups of digits into running times (or historical dates)

2. Devised in used “retrieval structure” to guide:

• Parsing of list in to units

• retrieval of items at test


SF: Chunking


SF: Retrieval Structure


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 36


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 37


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

psyco 350 lec #3 – slide 1 lecture 3 – psyco 350, a1 winter, 2011 n. r. brown

Documents

serial position curveprimacy

good recall

free recall tasklist

free recall taskpsyco

initial serial positions

stm vs ltm

ltm transfer

rehearsal recallanalysis