Forgetting

Basic model of memory

CUE

TARGET

We’ve talked about forgetting (failure to retrieve) occurring if you don’t have the right cues at retrieval.

The “right” cues are the ones that make you think of the material the same way that you did at encoding.

What’s the highway to Richmond?

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This cue doesn’t match the way you thought about the highway at encoding

What’s the highway to Richmond?

What’s the highway to Richmond?

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It’s also possible, though, that the cue is just fine, and it’s the connection that gets lost.

Also possible that it’s the memory itself that becomes degraded or lost

What’s the highway to Richmond?

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What’s the highway to Richmond?

What’s the highway to Richmond?

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What’s the highway to Richmond?

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Cue Bias

DecayOcclusionUnlearningRepression

Selective retrieval

Cue bias—you can’t get the cues back

• Usually thought to be due to aging

• May happen due to extreme context effects—the world is a different place and can’t be the same

Cue bias—childhood amnesia

What’s your earliest childhood memory?

Cue bias study (Simcock & Hayne, 2002)

• Children (2-3) are shown “the incredible toy shrinking machine.”

• Their vocabulary is also measured.

• One year later their memory for the machine is tested, and they describe it only using words that were in their vocabulary a year ago.

• Possible that cue bias is the reason for childhood amnesia—you can’t access pre-verbal memories because you experienced them differently

What’s the highway to Richmond?

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• Decay—loss is spontaneous

• Occlusion—loss is due to new learning; can only retrieve new memory

• Unlearning—loss is due to new learning

• Repression—loss is an active, unconscious process.

What’s the highway to Richmond?

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What’s the highway to Richmond?

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What’s the highway to Richmond?

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Decay--orderliness of forgetting

Woodworth & Schlossberg, 1952

If you put this on a logarithmic scale. . . .

The orderly, logarithmic rate of forgetting indicated to people that decay was responsible for forgetting.

Problems with decay

• Time alone doesn’t cause anything; it’s processes occurring in time that makes things happen

• Theory is difficult to test.

Ideal experiment to test decay

Encoding Test

Encoding Test

Time

Memory should decay here

Bad memory due to decay

What actually happens

Encoding Test

Encoding Test

Time

People think; opportunity for interference

Test

SleepEncoding

Memory equal due to decay

If decay is responsible for forgetting then what you do during the interval shouldn’t matter—the

rate of forgetting will be the same.

Jenkins & Dallenbach, 1924

What you do during the delay DOES matter.

OcclusionAn old response that is already in

memory competes with a new response you’re trying to learn.

Hugo Munsterberg tried putting his pocket watch in a different pocket

than he was used to, to see how often he would reach in the wrong

pocket.

Highway to Richmond?

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Tip of the tongue

Someone who hates women Misogynist

Navigational instrument for measuring the angular elevation of the sun above the horizon

Sextant

Long, narrow flat-bottomed boat used in the canals of venice.

Gondola

Occlusion

It sounds good, but probably doesn’t account for that much forgetting.

Unlearning

Learning new stuff causes unlearning of old stuff.

How to test?

What’s your phone number?

555-1111

Barnes & Underwood

Learn list of paired associates

Asked to produce both associates, and give lots of time; therefore minimize occlusion

Learn list of repairings of associates (varied how much practice)

Results

So they do get evidence for unlearning, but. . .

3

4

5

6

7

8

Mean

Corr

ect

Resp

on

ses

0 5 10 15 20 25

Trials on Second List

List 2

List 1

The unlearning account; change in association.

TER

FUNNY

TER

FUNNY TIRED

TER

FUNNY TIRED

TER

FUNNY TIRED

How do you know that it’s really unlearning, i.e., the association that’s

getting weaker? Maybe it’s just overwhelmed by the strength of the new

associate.

Volume metaphor

TER

FUNNY

TER

FUNNY TIRED

TER

FUNNY TIRED

TER

FUNNY TIRED

“TER-TIRED”

“TER-FUNNY”

Original learning is intact--no unlearning has taken place--but it’s hard to “hear” because the new learning is so robust.

Volume vs. OcclusionNote that this is NOT occlusion; it’s about how you interpret what you retrieve, NOT your ability to retrieve the right associate.

Repression

• Active forgetting of traumatic material

• Very difficult to prove, but probably does happen on occasion

• Much more frequent that traumatic events lead to good memory.

Common lore

• Repression is very effective—but the memory can be recovered & highly accurate (i.e., goes from 0% to 100%).

• Repressed memories may be recovered through hypnosis, or by imaging yourself as a child again, etc.

• Danger: hypnosis & “guided imagery” can plant memories

Evidence• Piaget’s kidnapping

• Loftus et al. (1996) “lost in a store” study.

• “Anal probe” study

Conclusion: repression is poorly understood, probably possible, but rare. Also likely that false repressed memories can be planted.

Selective Retrieval

Highway to Richmond?

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Selective retrieval

This idea is that retrieving some stuff actually makes the retrieval of related stuff get harder, and it does so because it affects the representation, not the association.

The idea is that cues are often associated not just with one memory, but with many;

you need to suppress these other memories in order to retrieve only the one

that you want.

An example: retrieval induced forgetting

Study

Fruit-orange

Fruit-banana

Drink-lemonade

Practice Retrieval

Fruit-or

Test

Fruit-or

Fruit-ba

Drink-leGood

Bad, relative to Drink-lemonade

Retrieval induced forgetting: is it selective retrieval?

Fruit

Banana

But it could also be

Fruit

Banana Orange

BUT, selective retrieval makes a unique prediction. . .

Fruit

Banana

If it’s the representation that’s inhibited, it should be inhibited even when accessed another way.

Yellow

Anderson & Spellman

Study categories and examples of categories, e.g., RED-BLOOD. If you study this, then the other examples of the category RED should be

harder to learn.

“RED”

“RED” Other red things are dampened so you can retrieve blood.

“RED”

If selective retrieval takes place, it will be harder to learn“FOOD-STRAWBERRY” after learning “RED-BLOOD” It will be hard to learn “FOOD-STRAWBERRY” because STRAWBERRY has been inhibited as RED-BLOOD was studied.

“FOOD”

“RED”

It’s should not be the case that FOOD-STRAWBERRY is hardto learn simply because all associates are now hard to learn.To test that, compare learning FOOD-STRAWBERRY to other subjects who learn FOOD-CRACKER.

“FOOD”

Study “RED-BLOOD”

Study “FOOD-STRAWBERRY”

Study “RED-BLOOD”

Study “FOOD-CRACKER”

22% correct

38% correct

Inhibition due to selective retrieval

does take place. BUT it could be that this effect we’ve described is relatively temporary; we don’t know that yet.

Summary

Most of the types of forgetting we’ve talked about seem somewhat temporary. It’s doesn’t sound like permanent loss; it sounds like temporary loss.

Does this mean that all learning is permanent? Forgettingoccurs only because other learning is interfering with accessto the learning we want to access?

Does this mean that all learning is permanent?

Before we take up this issue, you should realize that this proposition is

impossible to disprove.

All learning is permanent

• Spontaneous recovery

• Hypnosis

• Wilder Penfield experiments.

Spontaneous recovery

1. Often no way to verify2. Even if true, the fact that some memoriesare lost for a long time, yet are recoverabledoes not mean that all memories that are lost are recoverable.

Examples. . .?

Hypnosis

Hypnosis is perfectly real, and cool things can be done with it. It does nothing to help memory. It increasesconfidence in memory, butnot accuracy of memory.

Results from a hypnosis study

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Mean

corr

ect

reca

ll

0 1 2 3 4 5 6 7 8 9

Recall attempts

no hypnosis

hypnosis{

oneweek

allsubjects

awake fortrial 8

Wilder Penfield studies

Direct brain stimulation: usual report is full-blown recovery of forgotten memories.

What’s not reported:1) happened rarely: perhaps 7-8%2) no way to assess accuracy3) subjects saw themselves in memory,home-movie style, and reported that they were “dream-like”

In sum. . .

It’s impossible to disprove that everything that ever happened to you is recorded, but most memory researchers don’t believe this is the case.