PSY 368 Human Memory

Memory Forgetting

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Rapid forgetting for short delays - slower for longer delays

Ebbinghaus (1885)

• Memory isn’t always perfect (remember The 7 Sins)

• 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

Forgetting

Hyperthymestic Syndrome

• 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.

• Remembering feels “automatic” and not under conscious control.

• Can verify events with the diary she keeps.

• AJ’s superior memory has costs:

• She cannot forget unpleasant memories.

• Constant reminders are distracting and sometimes troubling.

5

• http://www.cbsnews.com/video/watch/?id=7166313n&tag=contentMain;contentBody

• Hyperthymestic Syndrome: Uncontrollable remembering

• We have seen pennies hundreds if not thousands of times. Draw one, the heads side.

What do we forget?

• 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

• 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

What do we forget?

Average answers

• Autobiographical Memory

What do we forget?

• Recollected events that belong to a person’s past• Personal milestones, emotional memories

• Why?• Life narrative hypothesis –

assume life identities during this time

• Cognitive hypothesis – encoding better in this period of rapid change

Rubin (1982, 1996) “Hill of Reminiscence”

• Reminiscence bump: Adolescence/early adulthood (change to stability)

Infantile amnesia

• Autobiographical Memory

What do we forget?

• Recollected events that belong to a person’s past• Personal milestones, emotional memories

• 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

Schrauf & Rubin (1998)

• Cultural life shift – culturally shared expectations structure recall.

What do we forget?

• 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.

Meeter, Murre, and Janssen (2005)

• 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

RecognitionRecall

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.

Bahrick, Bahrick & Wittlinger (1975)

Permastore

• 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

Bahrick, Bahrick & Wittlinger (1975)

Permastore

• Tested nearly 400 high-school graduates on their ability to recognize and name classmates after delays of up to 30 years.Results were mixed:

• Relatively unimpaired:• Ability to recognize their classmates’

faces/names. • Ability to match up names to the

appropriate portraits.

Conclusion:• Recall, but not recognition, of well-learned personal material,

closely follows the forgetting curve first demonstrated by Ebbinghaus (1913).

• Extensively impaired:• Ability to recall a name, given a person’s

portrait.

RecognitionName Matching

RecallName the picture

3.3 mons. 47+ yrs.

• 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.

Permastore

• Skills• Can vary in forgetting rate

What do we forget?

• 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

Fleishman & Parker, 1962

What do we forget?

McKenna & Glendon (1985)• First aid volunteers who

had mastered the skills• Performance and timing• Technique (inflate lungs and

press chess in right place)

• Diagnosis (check breathing and pulse)

• Total score (would the patient have survived)

• Over time their CPR abilities drop very quickly • Down to 10-15 % within

one yr

• Skills• Can vary in forgetting rate

Technique

Performance

Total score

Diagnosis

Months

Perc

en

tage

• Prospective memory (items 7, 14, 18)

• Remembering what you want to do (event-based)

• Remembering to do it at the right time (time-based)

What do we forget?

• Retrospective memory• Typically focused on What? questions

• Relatively new field of investigation, not as much known yet• Guest speaker: Dr. Dawn McBride will tell us more in April

• “Various studies have reported that 50-80% of everyday memory problems are, at least in part, prospective memory problems”

• Kliegel & Martin (2003)

• Prospective memory

What do we forget?

• 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”

• Typical Procedure

• Prospective memory

What do we forget?

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

• Theories of forgetting:• Failure of Consolidation• Failure of retrieval

• Decay• Context/cue mismatch • Interference

How do we forget?

• Structural changes in the synaptic connections between neurons.

• Relies on biological processes

• May take hours to days to complete.

• Memories remain vulnerable until these changes occur.

• The gradual shift of a memory’s reliance away from the hippocampus and to the cortex.

• Accomplished by repeatedly “replaying” a memory’s various components until they are interlinked.

• May take years to complete in humans.

• Memories are vulnerable until they become independent of the hippocampus.

Synaptic Consolidation Systemic Consolidation

Consolidation: The time-dependent process by which new memory traces are gradually cemented and interconnected in memory.

Types of Consolidation

• 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)

How do we forget?

• 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?

• Dog – Book• Tree - Cloud• Shoe - Car• Pen - Soda• Clip - Horn• Leaf - Cup• Truck - Ant• Fish - Goat• Lake - Peach

• Recall from first list• Dog – ?• Tree - ?• Shoe - ?• Pen - ?• Clip - ?• Leaf - ?• Truck - ?• Fish - ?• Lake - ?

• Dog – Bed• Tree - Cake• Shoe - Couch• Pen - Stool• Clip - House• Leaf - Chair• Truck - Apple• Fish - Gas• Lake - Penny

How do we forget?

• Dog – Book• Tree - Cloud• Shoe - Car• Pen - Soda• Clip - Horn• Leaf - Cup• Truck - Ant• Fish - Goat• Lake - Peach

• Recall from first list• Dog – ?• Tree - ?• Shoe - ?• Pen - ?• Clip - ?• Leaf - ?• Truck - ?• Fish - ?• Lake - ?

• Dog – Bed• Tree - Cake• Shoe - Couch• Pen - Stool• Clip - House• Leaf - Chair• Truck - Apple• Fish - Gas• Lake - Penny

Introducing a related second list of items impairs recall of the first list.

Introducing a related second list of items impairs recall of the first list.

• Proactive Interference (PI)

How do we forget?

• 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.

On a separate sheet of paper: Write down all the words from the 1st list - on front side - you

remember

Turn the paper over and study the list of words on the back page, one at a time, for 1 min.

How do we forget?

• List 1• 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

• Rose…tulips….• Rose....horse…• Same total number or

items learned

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

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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