Psyco 350 Lec #3 – Slide 1 Lecture 3 – Psyco 350, A1 Winter, 2011 N. R. Brown.
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Transcript of 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
Psyco 350 Lec #3 – Slide 2
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
Psyco 350 Lec #2 – Slide 3
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
Psyco 350 Lec #2 – Slide 4
Free Recall & the Serial Position Curve
Memory Tests
Recognition
Uncued
Serial
Cued
Recall
FREE
Psyco 350 Lec #2 – Slide 5
Free Recall Task
Psyco 350 Lec #2 – Slide 6
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.
Psyco 350 Lec #2 – Slide 7
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.
Psyco 350 Lec #2 – Slide 8
In-Class Serial Position Curve
0102030405060708090
100
1 3 5 7 9 11 13 15
Serial Position
% R
ecal
led
NoDelay
20 s Delay
Psyco 350 Lec #2 – Slide 9
Free Recall & the Serial Position Curve
• 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
Psyco 350 Lec #2 – Slide 10
Serial Position Curve
• Primacy: Good recall for 1st few items • Recency: Good recall for last few items on list
Psyco 350 Lec #2 – Slide 11
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
Psyco 350 Lec #2 – Slide 12
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
Psyco 350 Lec #2 – Slide 13
Rundus: Rehersal Protocols
Psyco 350 Lec #2 – Slide 14
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
Psyco 350 Lec #2 – Slide 15
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
Psyco 350 Lec #2 – Slide 16
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
Psyco 350 Lec #2 – Slide 17
Amnesia & Serial Position• Baddeley & Warrington
(1970)• H.M. – removal temporal
lobe and hippocampus• Clobbered Explicit
memory.• Yet – on immediate test,
recency intact
styd
Psyco 350 Lec #2 – Slide 18
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
Psyco 350 Lec #3 – Slide 19
Measuring STM Capacity: Memory Span Task
• Instructions: Recall the digits in the order presented.
Psyco 350 Lec #3 – Slide 20
Free Recall & the Serial Position Curve
Memory Tests
Recognition
Uncued
Serial
Cued
Recall
FREE
Psyco 350 Lec #3 – Slide 21
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
Psyco 350 Lec #3 – Slide 22
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”
Psyco 350 Lec #3 – Slide 23
Modal Model w/ 7 Slots – 1 chunk/slot
Psyco 350 Lec #3 – Slide 24
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
Psyco 350 Lec #3 – Slide 25
Extraordinary Digit-Span: SF
• Materials:– random digits
– auditory presentation
– 1 digit/s
• Results:– After 45 days of practice: span = 83
Psyco 350 Lec #3 – Slide 26
SF: Digit Span
Psyco 350 Lec #3 – Slide 27
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
Psyco 350 Lec #3 – Slide 28
SF: Chunking
Psyco 350 Lec #3 – Slide 29
SF: Retrieval Structure
Psyco 350 Lec #3 – Slide 30
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 #3 – Slide 31
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 #3 – Slide 32
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 33
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 #3 – Slide 34
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 #3 – Slide 35
Studying Retrieval from STM
Psyco 350 Lec #3 – Slide 36
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
Psyco 350 Lec #3 – Slide 37
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
Psyco 350 Lec #3 – Slide 38
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
Psyco 350 Lec #3 – Slide 39
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
Psyco 350 Lec #3 – Slide 40
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 #3 – Slide 41
Sternberg Task: Method
Psyco 350 Lec #3 – Slide 42
Competing Retrieval Model Predictions
Psyco 350 Lec #3 – Slide 43
Why Serial Models Make Different PredictionsAdditive Factors Logic (Radvansky, pp. 58-60)
Psyco 350 Lec #3 – Slide 44
Sternberg Task: Results
• RT w/ set size
Implication: serial
• Negative = PositiveImplication: exhaustive
Psyco 350 Lec #3 – Slide 45
Sternberg’s Model
Psyco 350 Lec #3 – Slide 46
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 #3 – Slide 47
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