Forgetting

1

MemoryInternal record or representation of past

experienceNot necessarily the same as the original

experienceHistory & metaphors

Slate Filing cabinet Computer

2

Types of MemoryMany different types of memory

2 are important for our purposes:Working memory: short-term, no need to store

each instance for future referencee.g. matching to sample: need to remember what

the sample was only until you make the choiceSamples change from trial to trial

Reference memory: long-term, remember specific information for future referencee.g. maze training: remember lay-out of the

maze, doesn’t change across trials

3

Working Memory

4

Sample:

Retention Interval:

Choice:

Remember “green”

Trial #1

Remember “red”

Trial #2

Remember “red”

Trial #3

Reference Memory

5

Start

Food

Trial #1 Trial #3

FoodStart

Trial #2Start

Food

Goal is always in the same place… remember over time!

Behaviorist View of MemoryNo need to discuss “representation”No focus on storage & retrievalExperience’s ability to change an organism’s

behaviour under certain conditionsStimulus control

6

ForgettingDeterioration in learned behaviour following

a period without practiceDefined behaviourally

Performance vs DescriptionNote: extinction is not the same as forgetting

7

Measuring ForgettingWorking memory

Sample (training)Retention interval (usually short…

seconds/minutes/hours)TestNext sample is different

Reference memoryTrainingRetention interval (can be much longer… days/weeks)TestSamples (training) are always the same

8

Free Recall MethodTrain, wait, testSee how much deterioration in performance“All-or-nothing” test of behaviourMay not be appropriate for complex tasksSome elements remembered, others not

9

Free RecallLearn:

BananaInterestingAnnoyBookComputer

Recall:___________________________________________________________________________

10

Prompted (Cued) RecallGive prompts to increase likelihood of

behaviourMeasure number of prompts needed to

produce behaviour

11

Cued Recall:Recall:

Ba_________In_________An_________Bo_________Co_________

12

Learn:BananaInterestingAnnoyBookComputer

Relearning MethodReinstall original training procedure after

retention periodHow many trials (or time) needed compared

to original training to return to initial level of proficiency?

Reacquisition

13

Relearning

Learn :BananaInterestingAnnoyBookComputer

Trial #1

Score = 2/5

Recall:Banana__________Annoy____________________

Recall:Banana__________AnnoyBook__________

Trial #2

Score = 3/5

Recall:BananaInterestingAnnoyBookComputer

Trial #3

Score = 5/5Total Trials on Initial Learning = 3

How many trials to relearn after a break (retention interval)? Difference = amount of forgetting

Recognition MethodSubject only has to identify material

previously learnedE.g., distinguish between original stimulus

and a number of distracter stimuli

15

RecognitionWhich words were

on the list?BananaOrangeInterestingAnnoyUglyComputerTableApple

16

Learn:BananaInterestingAnnoyBookComputer

Delayed Matching to SampleShow S+Wait (Delay =

Retention Interval)Choose from S+

and S-Working memory

only

Sample

Delay

Matching

17

Extinction MethodTrain two subjectsPut both on extinction, but one has delay

between training and extinction and the other doesn’t

Compare rate of extinction for two subjects

18

Extinction methods

19

Group 1 & 2Learning Phase

Group 1Extinction

break

Group 2Extinction

Compare amount of time

Gradient Degradation MethodEstablish stimulus control (discrimination

training)Measure generalization gradientRepeated measure gen. grad. over timeIf generalization gradient flattens, forgetting

20

Gradient degradation

21

Training: Establish gradient

No Forgetting

Forgetting

22

Is time a variable?Retention interval = Time between learning

and testingGreater the interval, less retained (i.e., more

forgetting)But, time is not an event (time doesn’t

account for forgetting)Need causal factors

23

Variables are:Degree of learning (overlearning)Prior Learning

FacilitationInterference

Subsequent LearningContext

24

OverlearningLearn to asymptote, then keep training

Learning list perfectly, then practice a few more times

Better recall for longerPoint of diminishing return

Not a linear relationship between overlearning and retention

i.e. 100% overlearning is twice as good as 50% overlearning

25

Krueger (1929)Adults learn 3 lists of 12 one-syllable nouns

List 1: go through list until they remember all 12

List 2: learn list perfectly, then go through again for half as many trials as it took to learn i.e. if they took 10 trials to learn perfectly, they go

through list another 5 timesGroup 3: learn list perfectly, then go through

again as many times as it took to learn i.e. another 10 times

Relearn after various intervals26

ResultsGreater amount of overlearning, less

forgetting100% overlearning better than 50%

overlearning50% overlearning way better than 0%

overlearningi.e. difference between 100% & 50% was LESS

THAN difference between 50% & 0%

27

Facilitation of Prior LearningPrevious experience makes something easier

to rememberMeaningful material easier to retain than

random materiale.g. Easier to learn a complete sentence than

12 random wordsPrior experience important in determining

what is meaningful (e.g., words in known or unknown language)

28

DeGroot (1966)Arranged chess pieces on board as if in the

middle of a gameChess masters and novices; 5 seconds to

observeMasters reproduced arrangement 90% of

time, novices only 40%Is this prior experience, or do chess masters

forget less than other people?

29

Chase & Simon (1973)Chess pieces placed randomly on boardMasters no better than novices at recallPast learning of “legal” arrangements is what

increased masters’ performance in deGroot (1966) study

30

Interference of Prior LearningProactive interferencePrevious learning interferes with recall of

newer learning

31

Studying proactive interferencePaired Associate Learning (PAL) technique

Subjects learn paired lists, tested with 1 item and must recall second

All learn A-C list, but some previously learned A-B list

In testing, give A and ask to recall CThose with A-B learning have more difficulty

recalling C when given A

32

PAL example1 group first

learns:Red-AppleCloud-ShoeCat-ShelfPlate-SpoonCarpet-Tent

Both groups then learn:Red-BookCloud-PaperCat-FencePlate-

NotebookCarpet-

Window

33

Both groups then RECALL:Red- ________Cloud- ________Cat- ________Plate- ________Carpet- ________

Levine & Murphy (1943)Proactive interference with attitudesDetermine initial attitude towards communism

Likert ScaleRead pro- and anti-communism passagesStudents who had prior pro-communist

attitudes forgot anti-communist elements of passages but remembered pro-elements (and vice versa)

Proactive interference because attitudes are not innate; effect of prior learning

34

Subsequent Learning (Interference)

Inactivity during retention interval leads to less forgetting than activity

Implies forgetting partly based on learning new material

Jenkins & Dallenbach (1924)

Rec

all (

%)

100

50

Hours after learning tested

0 2 4 6 8

sleep

awake

35

Retroactive InterferenceNew learning interferes with ability to recall

earlier learningPAL technique (opposite order)

Subjects learn A-C, but some then learn A-BTest by giving A and recalling CSubjects who learned A-B have worse recall for

C e.g. forgetting old phone numbers, license

plates, passwords

36

PAL exampleBOTH groups

first learns:Red-AppleCloud-ShoeCat-ShelfPlate-SpoonCarpet-Tent

1 group then learns:Red-BookCloud-PaperCat-FencePlate-NotebookCarpet-Window

37

Both groups then RECALL:Red- ________Cloud- ________Cat- ________Plate- ________Carpet- ________

Order is just “switched” from last example

ContextLearning occurs in a contextVarious stimuli around the learnerThese stimuli serve as cues to evoke a

behaviourIf stimuli absent, may have cue-dependent

forgettingStimulus controle.g. forgetting names when in a different

context

38

39

SD

Colour, size, shape, etc…

Cue set, set of SD’s, has changed! Less cues to signal correct response.

Perkins & Weyant (1958)Train two groups of rats in two mazes, one

black, one white1 minute retention intervalHalf of each group tested in original maze,

half in maze of opposite colourOpposite colour rats did poorly compared to

original maze tested rats

40

Kamin (1957)Gave rats

avoidance learning, tested at various retention intervals.

Time of day, internal clock

Internal physiological state cues recall

“internal” context

Avo

idan

ce (

%)

Retention Interval (hr)

0 12 24 36 48 60 72 84

100

50

41

State-Dependent LearningTrain under a particular physiological state

(e.g., drug condition) and test under various states

Recall best when in the same state as training

Drug conditions: alcohol, caffeine, etc.Internal State: tired, level of stress, emotions,

etc.

42

Application: ForagingFood Caching Cache: food storeRetrieval of food laterSpatial memoryWide variety of speciesAccuracy can be quite high for very long

times

43

Application: Eyewitness TestimonyNotoriously poorBasic issue of retention interval and

forgettingAlso the nature of the question used to

retrieve information

44

Loftus & Zanni (1975)Subjects watched film of car accidentAsked “Did you see <the>/<a> broken

headlight?”“the” subjects twice as likely as “a” subjects

to say “yes”Actually, no broken headlight shownReinforcement historyPrevious conditioning: “the” (definite article)

implies presence; “a” implies possible presence

45

Loftus & Palmer (1974)Watch film of car accident“How fast were the cars going when they hit

each other?”Underlined word replaced with smashed,

collided, bumped, contactedSpeed estimates varied based on wording of

questionReports of broken glass varied based on

wording

46

47

Learning to RememberIn essence, improving learningPractice increases retentionTechniques:

OverlearningMnemonicsContext cuesPrompts

48

OverlearningPractice beyond learninge.g. Tiger Woods putting practicee.g. Flash Cards (SAFMEDS)

49

MnemonicsRhymes, First Letters

HOMES, Roy G. BivMethod of Loci

Associate learned items with locations on a well-known route

Peg Word System1 = “bun”, 2 = “shoe”, 3 = “tree”…Also works with visual1 looks like a pencil, 2 looks like a swan, 3 is a

tricycle…

50

Mnemonic example1 – “coffee cup” – imagine using a coffee cup as a

pencil holder2 – “rubber ball” – imagine a swan holding a

rubber ball in its beak3 – “printer” – imagine a printer printing a piece

of paper with a tricycle on it4 – “yoga mat” – imagine trying to balance in

yoga positions while on top of a table (4 legs)Etc….The more bizarre the image, the easier it is to

remember (lack of interference)

51

PromptsCreating S+’sMemos, notes, calendar markings

Often don’t contain all info, so just a “reminder” of what needs to be done

E.g. “3-Choice meeting”String on finger, watch beep, cell phone

reminders

52