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Lecture 9 – Psyco 350, B1
Fall, 2011
N. R. Brown
Psyco 350 Lec #9– Slide 1
Outline
• Forgetting
– decay
– retrieval failure
– Interference
– Inhibition (directed forgetting)
• Interference In the Real-World
– Hindsight Bias
– Misinformation Effect
Psyco 350 Lec #9– Slide 2
Ebbinghaus(1885): The 1st Forgetting Function
• Main Findings:
– AMOUNT of forgetting decreases w/ time
• Interpretation:
– orgetting driven by decay; information lost at a constant
rate.
Psyco 350 Lec #9– Slide 3
A Sample Decay Function
100
% Recalled
90
80
time
start
X
finish
01
100
50
12
50
25
23
25
34
12.50
6.25
45
6.25
3.125
70
60
50
40
30
20
10
0
1
2
3
Study-Test Delay
4
5
• Rate of forgetting constant over time
• Amount of forgotten/unit time  with time
Psyco 350 Lec #9– Slide 4
.50
12.50
Studying PI & RI
• Classic studies: paired associate learning
– study: cue-target word pairs (CUP-tree)
– test: given cue, recall target (CUP-???)
– manipulate presence, timing & similarity of
additional targets
Psyco 350 Lec #9– Slide 5
Studying PI & RI
Design
Proactive
Retroactive
List 1
A-B
D-E
A-B
A-B
List 2 Test
A-C A-?C?
A-C A-?C?
A-C
D-E
A-?B?
A-?B?
Exp
Control
Exp
Control
General Findings:
•
•
Cued Recall: Control > Experimental
Similarity Effects: the more similar B is C, the more
server the interference.
Psyco 350 Lec #9– Slide 6
Yet Another Demo
•
•
•
•
4 list
8 words/list
Study  23 s of social interaction
Test – recall 8 words from prior list.
Psyco 350 Lec #9– Slide 7
PI & RPI
List 1
1
2
3
4
5
6
7
8
badger
caribou
wolverine
otter
rabbit
gopher
fox
seal
Psyco 350 Lec #9– Slide 8
List 2
goat
skunk
raccoon
squirrel
bear
cougar
elk
mouse
List 3
List 4
deer
walrus
mink
beaver
coyote
woodchuck
lynx
moose
Cleveland
Paris
Winnipeg
Dallas
Boston
London
Rome
Halifax
PI & RPI: Background
Brown & Peterson Task Review
• Task: learn triplet  filled delay  recall triplet
• Finding:
– recall drops off very rapidly w/ delay
• Original Interpretation:
– Forgetting caused by decay in STM
– Forgetting indicates the rate of loss from STM
• Alternative Interpretation (Keppel & Underwood):
– Forgetting caused by PI from similar materials
• Implication: PI should be reduced when new list
differs from prior lists.
Psyco 350 Lec #9– Slide 9
Release from PI: Wickens (1972)
• Task: Standard Brown-Peterson Task
• Procedure:
– Trials 1 though 3: triples drawn from same
semantic category
– Trial 4: triple drawn from different category
Psyco 350 Lec #9– Slide 10
Wickens (1972): Materials
Psyco 350 Lec #9– Slide 11
Wickens (1972): Results
• PI  (recall ) across
same-category trials.
• when category changes,
Recall 
Release from PI
• RPI  as similarity
between initial category
and new category 
• Finding generalize to realworld material (news stories)
Psyco 350 Lec #9– Slide 12
Gunter, Berry, Clifford (1981): RPI w/ News Stories
• Replicates Wickens with news stories.
e.g., 3 sets of political stories  1 human interest story
Psyco 350 Lec #9– Slide 13
RPI: Activation-Discrimination Interpretation
Activation:
• Concepts activated when accessed
• Activation decays rapidly
Retrieval: search some (cued) portion of memory for
most active concepts.
-------------------------------------------------------------------------PI: difficult to discriminate between many activated
concepts.
RPI: relatively easy to select active concepts among
inactive ones.
Psyco 350 Lec #9– Slide 14
RI -- Recent learning impedes recall of prior
material
Slamecka (1960) – a lab demonstration
Materials: 20-word long sentences drawn from
text books.
Study: Sentence present 1 word/3 seconds
Test: Verbatim recall
Design:
# Learning Trials X # Interpolated Trials
2
0
4
4
8
8
Psyco 350 Lec #9– Slide 15
Slamecka (1960): Results
IMPORTANT:
study-test delay constant
across interpolation
conditions
• Recall  w/ # learning
trials (rehearsal effect)
• Recall  w/ #
interpolated trials (RI)
Psyco 350 Lec #9– Slide 16
RI in the Real World
General Idea: New task-relevant information
makes to difficult or impossible to recall or
reconstruct prior beliefs, knowledge,
responses
A GOOD thing: knowledge revision (Friedman &
Brown, 2000)
And a BAD thing:
Hindsight Bias
Misinformation Effect.
Psyco 350 Lec #9– Slide 17
Hindsight Bias: Typical 3-Phase Design
Experimental Condition
Phase 1: respond to a target question  R1
• How many rhinos live in Africa?
Phase 2: Learn the answer to target question.
• There are 14,770 rhinos in Africa.
Phase 3: Recall initial response (R1).
Psyco 350 Lec #9– Slide 18
Hindsight Bias: Typical 3-Phase Design
Control Condition
Phase 1: respond to a target question  R1
• How many rhinos live in Africa?
Phase 2: Learn the answer to control question.
• The per capita GDP of Guam is $14,770.
Phase 3: Recall initial response (R1).
Psyco 350 Lec #9 – Slide 19
Hindsight Bias Design
A-B
A-C
A-?B?
Experimental Condition
A = # rhinos B = R1
A = # rhinos C = 14,770
A = # rhinos ?B? = R1
A-B
D-E
A-?B?
Control Condition
A = # rhinos B = R1
D = Guam GDP C = 14,770
A = # rhinos ?B? = R1
Psyco 350 Lec #9– Slide 20
Hindsight Bias(es)
Recollection Bias:
Correct recall of R1: Control > Experimental
Reconstruction Bias (when R1 not recalled):
In Exp Condition -- Phase 3 response shifted in
direction of Phase 2 information
In Control Condition – Phase 2 information has
no affect on Phase 3 response
Psyco 350 Lec #9– Slide 21
Hindsight Bias: 2 mechanisms for 2 biases
Recollection Bias:
• standard associate interference (Phase 2 answer
competes w/ R1)
Reconstruction Bias:
• Phase 2 information cause a revision of underlying
beliefs
• When R1 not retrieved, answer reconstructed w/
revised information
Psyco 350 Lec #9 – Slide 22
Misinformation Effect
General Phenomenon:
• memory for events distorted by exposure to
inaccurate/misleading post-event information
– benign aspect: post-event narration/discussion
can alter autobiographical memories
– forensic issue: post-event questioning can
alter eyewitness testimony.
Psyco 350 Lec #9 – Slide 23
Misinformation Effect: Basic Paradigm
An event is witnessed (on tape)
Post-event questioning used to introduce
misinformation.
• Correct Post-event Information
– Did the repairman set down his hammer before taking the
calculator?
• Misleading Post-event Information
– Did the repairman set down his screwdriver before taking the
calculator?
• Neutral
– Did the repairman set down his tool before taking the calculator?
Psyco 350 Lec #9– Slide 24
Misinformation Effect: Basic Paradigm
Test: Recognition for details of original event
2IFC = two item forced choice
Did you see a hammer or a screwdriver?
Finding:
% correct as a function of post-event info type:
correct > neutral >> misleading
Psyco 350 Lec #9 – Slide 25
Loftus, Burns, Miller (1978)
Materials:
– 30 slides; pedestrian being hit.
– traffic sign (STOP) appears in 1 slide.
Questioning:
– “Did another car pass the red Datsun as it passed
the STOP/YIELD sign?”
• Delay: 20 min
• Test: 2IFC picture recognition
picture w/ STOP vs picture w/ YIELD
Psyco 350 Lec #9 – Slide 26
Loftus, Burns, Miller (1978)
• Results:
– Accurate post-event info: 75% cor.
– Misleading post-event info: 40% cor.
• Loftus’ Interpretation: Memory change theory
(knowledge revision)
– misleading information replaces the original,
which is permanently lost
Psyco 350 Lec #9 – Slide 27
Misinformation Effect: Other Interpretations
Memory Coexistence (RI)
• Misleading information obscures original
memory because it is more recent
• Support:
– Memory better when original context is
reinstated
– Memory better if people are warned of
misleading information before test
Psyco 350 Lec #9 – Slide 28
Misinformation Effect: Other Interpretations
Source Monitoring Failure
• Errors reflect a failure to identify the source
– People remember information, but misremember
where it came from
• Information that people are mislead about is
often that which they make source errors for
Psyco 350 Lec #9 – Slide 29
Misinformation Effect: Other Interpretations
Biased Guessing Account
McCloskey & Zaragoza (1985)
• Central Notions:
– Target and Foil (misinformation) can coexist
– Either or both can be forgotten
– Magnitude of misinformation effect depends on:
• Prob (Target recalled)
• Prob (Foil recalled)
• %(Foil selected over Target)
Psyco 350 Lec #9 – Slide 30
Biased Guessing Account
Magnitude of misinformation effect depends on:
• Prob (Target recalled)
• Prob (Foil recalled)
• %(Foil selected over Target)
Implication:
If foil removed from reco test, then
MISLED = CONTROL
Reason:
“remembered” misleading inform no longer competing
with original info.
Psyco 350 Lec #9 – Slide 31
Testing Biased Guessing Hypothesis
Initial Event Post-Event
Reco Test
Control
“Stop”
---
“Stop” or “Yield
Standard – Accurate
“Stop”
“Stop”
“Stop” or “Yield”
Standard -- Misleading
“Stop”
“Yield”
“Stop” or “Yield”
Modified – Misleading
“Stop”
“Yield”
“Stop” or “Detour”
• Introduce modified recognition test.
• Predictions for recognition accuracy:
– Biased Guessing: Modified Misleading = control
– Memory Change: Modified Misleading < control
• misleading info should  memory for original info regardless of
test
Psyco 350 Lec #9 – Slide 32
Rationale for Biased Guessing Prediction
Control Condition: “S”  no “Y”; test: “S” or “Y”
“S,” no “Y”
no “S,” no “Y”
Standard Test: “S”  “Y”; test: “S” or “Y”
“S,” no “Y”
“S,” “Y”
no “S,” “Y”
no “S,” no “Y”
Modified Test: “S”  “Y”; test: “S” or “Z”
“S,” no “Z”
no “S,” no “Z”
Psyco 350 Lec # 9 – Slide 33
McCloskey & Zaragoza (1985): Method
Stims:
– 79 slides of an office theft
– 4 s / slide
– 4 critical items: coffee jar, magazine, pop can, tool
– Post-slide narrative
• 735-words long
• misinformation for 2 items; neutral for 2 items
Psyco 350 Lec # 9 – Slide 34
McCloskey & Zaragoza (1985): Method
Procedure:
• view slides
• 10 minute filler
• read narrative
• 10 minute filler
• 36-item 2IFC recognition test:
“The man slide the calculator beneath the ___ in his tool box”
standard test:
hammer vs screwdriver
modified test:
hammer vs wrench
Psyco 350 Lec # 9 – Slide 35
McCloskey & Zaragoza (1985): Method
Procedure:
• view slides
• 10 minute filler
• read narrative
• 10 minute filler
• 36-item 2IFC recognition test: In Narrative
“The man slide the calculator beneath the ___ in his tool box”
standard test:
hammer vs screwdriver
modified test:
hammer vs wrench
Psyco 350 Lec # 9 – Slide 36
On Slide
Never encountered
McCloskey & Zaragoza (1985): Results
Standard
Misled
Control
37%
72%
72%
75%
hammer vs screwdriver
Modified
hammer vs wrench
• Standard Test:
– replicates Misinformation effect: Misled << Control
• Modified Test:
– consistent w/ Biased Guessing: Misled  Control
• access to original info unimpaired by post-event info.
• Consistent w/ Coexistence & Source Monitoring Accounts
Psyco 350 Lec # 9 – Slide 37
Misinformation w/ Modified Procedure: Belli (1992)
Materials:
– 44 slides (mother & child arguing)
– 4 crit slides (coffeemaker, blender, toaster)
– 500 word narrative w/ 2 misleading statements
• 2IFC modified reco test
Slide
Narrative
Test
Control
toaster
---
toaster vs blender
Mod
Misinfo
toaster
coffemaker
toaster vs blender
Psyco 350 Lec # 9 – Slide 38
Misinformation w/ Modified Procedure: Belli (1992)
Design – manipulates timing of misinformation
view slides


Exp1 5-min delay
Exp3 5-day delay

read narrative

10 min delay

reco test
Psyco 350 Lec # 9 – Slide 39
Belli (1992): Results
Exp 1ns: 5-min delay
Control
95%
Mod Mis
95%
Exp 3*: 5-day delay
80%
70%
• W/ 5-min delay:
Mod Misled = Control
• consistent w/ Biased Guessing
• W/ 5-day delay:
Mod Misled < Control
• (at lease) consistent w/ Coexistence & RI
Psyco 350 Lec # 9 – Slide 40
Blocking Hypothesis: Belli’s Explanation
Post-event information impairs access to original traces
when:
• original trace is weak
• post-event information is strong
Original
trace
Trace for
Effect of mis-info
misinfomation on modified test
strong
strong
no
M&Z
weak
weak
no??
??
weak
strong
yes
Belli
Psyco 350 Lec # 9 – Slide 41
Misinformation Effect: My Take
Memory impairment, coexistence, & source monitoring errors are
not mutually exclusive
• As the work on Hindsight bias indicates, new information can:
– modify existing information
– coexist w/ existing information
– block access to existing information
•
Biased guessing is a problem in 2IFC situation – particularly
when target & misinformation are of equal strength
• Nonetheless, bias to select foil in standard condition, indicates
that post-event information is (some times) accepted as true &
incorporated into event representation.
Psyco 350 Lec # 9 Slide 42