PSY 368 Human
Memory
Memory Forgetting
Announcements
• Processing views homework due Web Feb 29
• Craik and Lockhart (1972) download, read, and
answer focus questions, due Monday Feb 27
Forgetting
• Memory isn’t always perfect (remember The 7 Sins)
Memory
Performance
Ebbinghaus (1885)
Rapid forgetting for short
delays - slower for longer
delays
Forgetting
• Memory isn’t always perfect (remember The 7 Sins)
• What do we forget?
• Retrospective Autobiographical memory
• Prospective memory
• How do we forget?
• Failure of Consolidation
• Failure of Retrieval
• Decay
• Interference
• Context/cue mismatch
Hyperthymestic Syndrome
• Hyperthymestic Syndrome: Uncontrollable remembering
•
http://www.cbsnews.com/video/watch/?id=7166313n&tag=contentMain;contentBody
• Parker, Cahill, and McGaugh
(2006)
• Case study of AJ, 41 years old
• Remembers every day of her
life, in detail, since her teens.
• Feels as though she relives the
events she remembers.
• Can verify events with the
diary she keeps.
• AJ’s superior memory has
costs:
•
•
• Remembering feels “automatic”
and not under conscious control.
5
She cannot forget unpleasant
memories.
Constant reminders are
distracting and sometimes
troubling.
What do we forget?
• We have seen pennies hundreds if not thousands of
times. Draw one, the heads side.
• What does it say?
• Which way does the head face?
Nickerson & Adams, (1979)
• Memory for the common penny
quite bad.
• Less than half the people
correctly identified its features
What do we forget?
• Everyday Memory Questionnaire
• Questions about things people typically forget
• Assesses memory abilities
• Typical score = 58
• Higher scores indicate worse memory abilities for everyday
tasks
• Has been used to assess memory deficits in brain injury
patients
• Can also indicate possible dementia
Average answers
What do we forget?
• Autobiographical Memory
• Recollected events that belong to a person’s past
• Personal milestones, emotional memories
Rubin (1982, 1996) “Hill of Reminiscence”
• Reminiscence bump:
Adolescence/early adulthood
• (change
Why? to stability)
•
•
Life narrative hypothesis – assume
life identities during this time
Cognitive hypothesis – encoding
better in this period of rapid
change
Infantile amnesia
What do we forget?
• Autobiographical Memory
• Recollected events that belong to a person’s past
• Personal milestones, emotional memories
Schrauf & Rubin (1998)
• Cultural life shift – culturally shared
expectations structure recall.
•
The reminiscence bump for people
who emigrated at age 34 to 35 is
shifted toward older ages, compared
to the bump for people who
emigrated between the ages of 20 to
24
What do we forget?
Meeter, Murre, and Janssen (2005)
• Measured the forgetting rate for people’s memory of widely publicized
events from verifiable sources (headlines and TV broadcasts).
• Task: 14,000 participants completed an internet questionnaire, assessing recall
and recognition for 1,000 dateable events.
• Results: Like the Ebbinghaus results, recall for events shows a steep initial
drop, followed by a slower forgetting rate.
• Recall for events dropped from 60%
to 30% in a year, then stayed
constant.
• Recognition was overall better, but
showed a similar pattern of results
Recognition
Recall
What do we forget?
• Permastore:
• Describes the leveling off of the forgetting curve at long delays.
• Beyond this point, memories appear impervious to further
forgetting.
Bahrick (1984)
• Permastore
• Rapid forgetting of foreign
language for 3 yrs,
• Then of a asymptotes (levels off)
after about 2 years,
• Stays fairly constant even up to 50
yrs.
• The overall level of retention is
determined by the level of initial
learning.
Permastore
Bahrick, Bahrick & Wittlinger (1975)
• Tested nearly 400 high-school graduates on their ability to recognize
and name classmates after delays of up to 30 years.
• Questions
• Recall
• Can you list all your classmates?
• Can you name all these faces?
• Recognition
• Is this the name of a classmate?
• Is this the face of a classmate?
• Match these names and faces
Permastore
Bahrick, Bahrick & Wittlinger (1975)
• Tested nearly 400 high-school graduates on their ability to recognize
and name classmates after delays of up to 30 years.
Recognition
Name Matching
Results were mixed:
100
Percent Correct
90
• Relatively unimpaired:
80
70
• Ability to recognize their classmates’
60
50
faces/names.
40
30
Recall
• Ability to match up names to the
20
Name the picture
appropriate portraits.
10
0
3.3 mons.
47+ yrs.
• Extensively impaired:
Time since Graduation
• Ability to recall a name, given a person’s portrait.
Conclusion:
• Recall, but not recognition, of well-learned personal material, closely follows
the forgetting curve first demonstrated by Ebbinghaus (1913).
Permastore
• Bahrick studies
• Bahrick, Bahrick & Wittlinger (1975) – Studied memory of faces
from high school.
• Bahrick & Phelps (1987) – Studied knowledge from school,
learning Spanish and algebra.
• Bahrick, Bahrick, Bahrick, & Bahrick (1993) – benefits of
distributed practice (13 or 26 sessions) on long term retention of
300 pairs of English and foreign words.
• Barhrick et al. (1996) – remembering high school grades,
accurately remember A grades (89% accurate) but not D grades
(29% accurate). Of Ps 79/99 inflated grades, more likely to
remember positive events than negative events.
What do we forget?
• Skills
• Can vary in forgetting rate
Fleishman & Parker, 1962
• Taught flying skills, Flying a
plane (simulated)
• Re-tested after 9 months, 1
year, and two years (no
practice)
• Later performance was at
same performance as it was
following the initial training
• Very little forgetting of this
skill
What do we forget?
• Skills
• Can vary in forgetting rate
McKenna & Glendon (1985)
• First aid volunteers who had
mastered the skills
chess in right place)
• Diagnosis (check breathing and pulse)
• Total score (would the patient have
Technique
Performance
Total score
Percentage
• Performance and timing
• Technique (inflate lungs and press
Diagnosis
survived)
• Over time their CPR abilities
drop very quickly
• Down to 10-15 % within one yr
Months
What do we forget?
• Retrospective memory
• Typically focused on What? questions
• Prospective memory (items 7, 14, 18)
• Remembering what you want to do (event-based)
• Remembering to do it at the right time (time-based)
• “Various studies have reported that 50-80% of everyday memory
problems are, at least in part, prospective memory problems”
• Kliegel & Martin (2003)
• Relatively new field of investigation, not as much known yet
• Guest speaker: Dr. Dawn McBride will tell us more in April
What do we forget?
• Prospective memory
• Typical Procedure
• Have two tasks, a main task and a secondary task (the
prospective task)
• “While you are performing this task (e.g., reading a list of
words), if you see a word corresponding to an animal with
fur, press the ‘1’ button”
What do we forget?
• Prospective memory
Einstein, McDaniel, Manzi, Cochran & Baker (2000)
• Task
• Primary: Read three sentences
• Secondary: press F1 key if read
“technique” or “system”
• Either right away
• Or after a delay (~40 s later)
• Result
• Even with very short delay, a
large drop in performance
How do we forget?
• Theories of forgetting:
• Failure of Consolidation
• Failure of retrieval
• Decay
• Context/cue mismatch
• Interference
Types of Consolidation
Consolidation: The time-dependent process by which new memory
traces are gradually cemented and interconnected in memory.
Synaptic Consolidation
•
Structural changes in the synaptic
connections between neurons.
•
Relies on biological processes
Systemic Consolidation
•
• Accomplished by repeatedly
“replaying” a memory’s various
components until they are interlinked.
• May take hours to days to
complete.
•
The gradual shift of a memory’s reliance
away from the hippocampus and to the
cortex.
• May take years to complete in
humans.
Memories remain vulnerable until
these changes occur.
•
Memories are vulnerable until they
become independent of the
hippocampus.
How do we forget?
• Sleep and Consolidation
• During sleep, neurochemical activity consolidating memories
• Retention of info is better if sleep follows study (Ekstrand, 1972)
• Empson and Clarke (1970) showed that when REM sleep vs.
other sleep stages were interrupted, worse memory for info
studied before sleep
How do we forget?
• Decay
• Info is lost from memory over time
• Applies to working memory and priming effects (activation
levels).
• A potential biological basis of decay:
• Neurons die and synaptic connections degrade over time, along with the
associated learned behavior.
• Trace decay is difficult to prove behaviorally because:
• It is necessary to rule out alternative sources of forgetting, including:
• Rehearsal
• Interference from any new experiences/memories.
• It is typically impossible to show whether the memories are unavailable or just
inaccessible.
How do we forget?
• Context/cue mismatch
• See last lecture
• Failure to retrieve because cues available at retrieval and the
ones present during encoding are different.
How do we forget?
• Interference (McGeoch, 1932)
• Info encoded before or after can interfere
• Storing similar memories impedes retrieval.
• Over time, many similar experiences occur, especially since
people are creatures of habit.
• Two types:
• Retroactive = info that comes AFTER interferes
• Proactive = info that comes BEFORE interferes
How do we forget?
• Retroactive Interference (RI)
• Forgetting caused by encoding new traces into memory in
between the initial encoding of the target and when it is tested.
• Introducing a related second list of items impairs recall of the first
list compared to a control condition.
How do we forget?
• Recall from first list
•
•
•
•
•
•
•
•
•
Dog – Book
Tree - Cloud
Shoe - Car
Pen - Soda
Clip - Horn
Leaf - Cup
Truck - Ant
Fish - Goat
Lake - Peach
•
•
•
•
•
•
•
•
•
Dog – Bed
Tree - Cake
Shoe - Couch
Pen - Stool
Clip - House
Leaf - Chair
Truck - Apple
Fish - Gas
Lake - Penny
•
•
•
•
•
•
•
•
•
Dog – ?
Tree - ?
Shoe - ?
Pen - ?
Clip - ?
Leaf - ?
Truck - ?
Fish - ?
Lake - ?
How do we forget?
Introducing a related second list of items
impairs recall of the first list.
• Recall from first list
•
•
•
•
•
•
•
•
•
Dog – Book
Tree - Cloud
Shoe - Car
Pen - Soda
Clip - Horn
Leaf - Cup
Truck - Ant
Fish - Goat
Lake - Peach
•
•
•
•
•
•
•
•
•
Dog – Bed
Tree - Cake
Shoe - Couch
Pen - Stool
Clip - House
Leaf - Chair
Truck - Apple
Fish - Gas
Lake - Penny
•
•
•
•
•
•
•
•
•
Dog – ?
Tree - ?
Shoe - ?
Pen - ?
Clip - ?
Leaf - ?
Truck - ?
Fish - ?
Lake - ?
How do we forget?
• Proactive Interference (PI)
• The tendency for older memories to interfere with the retrieval of
more recent experiences and knowledge.
• The number of previous learning experiences (e.g. lists) largely
determines the rate of forgetting at long delays.
Demo
Study the list of words on the front page (see the
highlighted 1), one at a time, for 1 min.
Turn the paper over and study the list of words on the
back page, one at a time, for 1 min.
On a separate sheet of paper: Write down all the words
from the 1st list - on front side - you remember
How do we forget?
• List 1
•
•
•
•
•
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•
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Tulip
Daisy
Hydrangea
Orchid
Violet
Magnolia
Carnation
Rose
Lilac
• List 2a
•
•
•
•
•
•
•
•
•
Dandelion
Pansy
Iris
Gardenia
Daffodil
Lily
Peony
Geranium
Marigold
• List 2b
•
•
•
•
•
•
•
•
•
Cheetah
Horse
Skunk
Llama
Mouse
Raccoon
Lemur
Rabbit
Monkey
How do we forget?
• Release from PI (2nd list doesn’t interfere as much)
• Change in item type can release interference
• Learn 2 lists of flowers vs. 1 of flowers and 1 of animals
• Rose…tulips….
• Rose....horse…
• Same total number or
items learned
Recal of
1st
50
45
40
35
30
25
20
15
10
5
0
All flowers
Flowers & Animals
Lists learned
Summary
(1) Tend to remember faces, languages, some skills for
very long time - permastore
(2) Identification forgotten
(3) Forgetting due to decay and/or interference
(retroactive, proactive) and/or lack of consolidation
Everyday memory Q
• Average ratings given by public in general
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5
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2
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3
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1
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3
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1
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1
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Back to lecture
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