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5 – Forgetting Demo: On a penny, what appears to the left of Lincoln? To the right? We forget almost everything we once knew. What causes forgetting? Can forgetting be avoided or at least diminished? . Scenario 3:00 pm 4:00 pm 5:00 pm

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5 – Forgetting

Demo: On a penny, what appears to the left of Lincoln?

To the right?

We forget almost everything we once knew.

What causes forgetting?

Can forgetting be avoided or at least diminished?



3:00 pm 4:00 pm 5:00 pm

You study History French Lab History exam

Your Friend study History rest History exam

Does the French Lab affect the score on History Exam?

Two possibilities:

“no” decay

amount forgotten depends solely on time elapsed since event


learning A interferes with the learning of B



Ss studied nonsense syllables

Then Ss slept or remained awake for 0 – 8 hours

Ss given test


Decay: Sleep = Awake

Interference: Sleep > Awake


(Jenkins & Dallenbach, 1924)





0 8

Test Delay (h)


Follow-up Experiment

Roaches learned to avoid shock.

Then placed on treadmill or squeezed in matchbox.

 1 day later, “still” Ss showed no forgetting.

(Minami & Dallenbach, 1946)

Karl M. Dallenbach



Ss played on rugby team. All Ss missed at least one game during the season.

Example Games

1 2 3 4 5 6 7 8 9

Player A      

Player B   

Sample Test Question

After game 9, Ss were asked “Who did you play in the 1st game?”


Decay: accuracy depends on # of days since 1st game A = B

Interference: accuracy depends on # of games played since 1st game A < B

Results supported interference.

(Baddeley & Hitch, 1977)


Two kinds of interference:

Proactive Interference (PI): prior learning hinders subsequent learning

Day 1 Day 2 Day 3

PI group Spanish French Test on French

Controls - - - - - - French Test on French

PI occurred if PI group did worse

Retroactive Interference (RI): subsequent learning hinders prior learning

Day 1 Day 2 Day 3

RI group Spanish French Test on Spanish

Control Group Spanish - - - - - - Test on Spanish

RI occurred if RI group did worse



In 10th grade, Brielle took French 1

In 11th grade, she took Spanish 1.

In 12th grade, she took Spanish 2.

On the first day of Spanish 2, she took pop quiz. For green, she wrote “vert.” (French)

What kind of interference explains her error?



French Spanish Spanish Quiz

Prior learning interfered with what she was trying to remember



Today, for the first time in her life, Jill used a numeric keypad.

She entered data for about an hour.

Then she phoned her friend.

(She has used a phone all her life.)

When she tried to press “9,” she mistakenly pressed “3”.

What kind of interference explains her error?


Use phone (before today) use keypad Test on phone

subsequent learning interfered with what she was trying to remember



A Brit flies to Tampa for his first trip outside the UK.

He rents a car and drives around Tampa for several days.

Then, while in Tampa, and while driving on narrow road at night, he sees oncoming car.

He veers left.

What kind of interference explains his error?


drive in UK drive in US test on US learning


Associated Press- Tampa - November 29, 2002

“A driver killed in a high-speed, head-on collision Wednesday after crossing the Sunshine Skyway on the wrong side was identified Thursday as a British citizen.”


Why does Proactive Interference occur?

Usually, PI occurs only if cue is paired with more than one target.


1:00 pm2:00 pm3:00 pm

study French (red-rouge) study Spanish (red-rojo) Spanish test (red-?)




This explanation of interference is called cue overload theory

(e.g., Watkins, 1977)


Example of cue overload theory

Today, Joe parked in the same lot for the 10th consecutive day (different spot each day)

cue = where in this lot did I park?

cue is paired with 10 targets

cue overload  cannot find car

Today, Moe parked in a lot the first time

cue = where in this lot did I park?

cue is paired with 1 target

No cue overload  can find car


Why does Retroactive Interference occur?

Sometimes, RI occurs because cue is paired with more than target.


1:00 pm2:00 pm3:00 pm

study French (red-rouge) study Spanish (red-rojo) French test (red-?)


But RI happens even if cue is linked to only one target


1:00 pm2:00 pm3:00 pm

study French (red-rouge) study History French test (red-?)

History impairs French test score!

So cue overload theory cannot be only cause of RI.


consolidation theory

1. Memory needs time to strengthen or “consolidate.” jello must harden

2. Until consolidation is complete, memory is vulnerable. jello can spill

3. Consolidation is disrupted by concurrent new learning. fridge door open


1:00 pm2:00 pm3:00 pm

Mr. X study French study History Test on French

Mr. Y study French rest Test on French

Mr. X does worse because studying History impaired consolidation of French

(e.g., Wixted, 2005)


Evidence for Consolidation

Observational data

After car accident, victim cannot recall last 15 minutes prior to accident.


ECT = electroconvulsive therapy

Mr. X study …ECT…………………………………….test

Mr. Y study ………………………………….ECT……test

Mr. X does worse. ECT erased memory before it had a chance to consolidate.

(Ribot, 1881; Squire et al.,. 1975)



One day, Ned and Fred studied History.

Then, Ned napped while Fred studied French.

Then, they took History test.

Ned History (1492  Columbus) Nap History Test (1492-?)

Fred History (1492  Columbus) French (dog-chien) History Test (1492-?)

According to consolidation theory, who should do WORSE?

Fred. His nap impaired consolidationof History.



One day, Holly and Spence studied French vocabulary

Then, Holly studied History while Spence studied Spanish.

Then, they took French vocabulary test.

Holly French (dog-chien) History French Test (dog-?)

Spence French (dog-chien) Spanish (dog-perro) French Test (dog-?)

a. According to cue overload theory, who should do WORSE?

Spence because his cue (DOG) is paired with 2 targets – not just 1.

b. According to consolidation theory, who should do WORSE?

Equally poor. For each, consolidation disrupted.



Often times, we cannot recall item but we can recognize it.

Example You cannot recall his name, but you would recognize it if you heard it.

Other times, we can neither recall nor recognize.

How should we measure recognition?


Yes-No Recognition method


Study: S is shown 4 words: girl, wall, rope, sign

Test: S is shown 4 original words (targets) and 5 new words (foils), one at a time.

Test ItemItem TypeDid you see it before?

rain foil no

sign target yes hit = said yes to target

boat foil no

wire foil no

food foil yes false alarm = said yes to foil

girl target no

rope target yes hit

rake foil no

wall target yes hit



Hypothetical Experiment

Study phase: Each S saw 50 face photos, one at a time.

Test. Each S saw random mix of the 50 old faces (targets) and 80 new faces (foils).

For each face, S was asked if he or she recognized face.

Jane said “yes” to 40 targets and 20 foils.

1. Find H.

2. Find FA.


Why measure both H and FA?

H is not sufficient. Why?

A subject could simply say “yes” to every item and achieve perfect score (100%)

FA is not sufficient. Why?

A subject could simply say “no” to every item and achieve perfect score (0%)


But measuring both Hit rate (H) and False Alarm rate (FA) can lead to ambiguity.


Ann: H = 80% FA = 60%

Ben: H = 50% FA = 20%

Who did better?

Ann had better H, but Ben had better FA.

Thus, we need a single measure that combines H and FA.

A simple but crude measure is H – FA

A better measure is d’ (“d prime”), which is beyond the scope of this course.



A researcher conducts a face recognition experiment.

During the study phase, Ss saw dozens of faces, one at a time.

During the test, Ss saw a random mix of the original faces and many new faces.

For each face, S was asked, ”Do you recognize this face?”

1. Anna performed perfectly. Find H – FA.

H = 100% FA = 0% H – FA = 100%

2. Beth said “yes” to every face. Find H – FA.

H = 100% FA = 100% H – FA = 0%

3. Carol said “no” to every face. Find H – FA.

H = 0% FA = 0% H – FA = 0%

4. Donna flipped a coin for each test face (heads = yes). Estimate H – FA.

H = 50% FA = 50% H – FA = 0%

5. For Emma, H = 10% and FA = 90%. What can you conclude?

She misunderstood instructions or sabotaged your experiment.


Face Memory Demo

You’ll see several faces, one at a time.

Just look at each face.


Get ready for Test phase

You’ll see 14 faces.

Your page is numbered 1 – 14.

For each test face, write “yes” or “no”


If your answer is yes, also write

1 if face appeared in Part 1 (these faces had blue border)


2 if face appeared in Part 2 (these faces had orange border)


Source Memory Demo



3 target Part 2



6 target Part 2




10 target Part 1

11 target Part 1




H = / 4 =

FA = / 10 =

H – FA =


Source Memory

Often we can recall a fact while forgetting its source

Where I did I read that?

Who told me that?

When did I learn that?


You know that Alaska is the largest state, but you cannot recall where you learned this.

You know that Bunny broke up with Chad, but you cannot recall who told you this.



Ss studied list of non-famous names (List 1)

½ Ss waited a minute, and ½ Ss waited a day

Ss given List 2 and asked to circle famous names. List 2 includes

famous names

new non-famous names (not seen before)

old non-famous names (from List 1)

Results minute delayday delay

circled famous name (correct) often often

circled new non-famous name (error) rare rare

circled old non-famous name (error) rare often

Conclusion: After a day, Ss forgot the source of their memory

(Jacoby, Kelley, Brown, & Jsechko, 1989)


Observational Study

In 1974, John Dean gave senate testimony about Watergate Scandal

His memory of oval office conversations was amazingly detailed.

Later, he, senate, and public learned that president secretly recorded conversations.

Detailed comparison of testimony and tapes revealed

Dean correctly recalled the gist of what was said

Dean was often wrong about who said it and when it was said

In other words, he made source memory errors.

(Neisser, 1981)


Common Criticism of Forgetting Research

Too many lab studies use procedures that are irrelevant to real world.


learning a list of unrelated words

testing subjects just 20 seconds after they studied the material

In other words, most memory research lacks ecological validity.

In recent decades, more forgetting studies use ecologically valid tasks.


Remember to take medicine (Einstein, 2000)


Forgetting Study

Ss were tested on their memory of names and faces from high school class

Time since graduation = 2 weeks - 57 years

Six tests, including cued name recall (see face photo, give name)

Sample Result

Time Since GraduationCued Name Recall Accuracy

3 months 70%

25 years 50%

In general, all 6 tests revealed surprisingly little forgetting.


Heavy, repeated exposure produces less forgetting than lab studies suggest.

(Bahrick, Bahrick, & Wittlinger, 1975)


Yearbook study

Bahrick, Bahrick, and Wittlinger (1975)


Author Demo

Try to recall the author of each book.


  Pride and Prejudice J A Jane Austen

War and Peace L T Leo Tolstoy

Canterbury Tales G C Geoffrey Chaucer

The Origin of Species C D Charles Darwin

Gone with the Wind M M Margaret Mitchell

Les MiserablesV H Victor Hugo


retrieval failure

Memory cannot be recalled but it is not forgotten


I could not recall her name, but I recognized it as soon as I heard it.

I could not recall who first sailed around world, but his name came to me later.

I cannot recall who assassinated Robert Kennedy, but his name begins with an S.


Tip-of-the-Tongue experience


Ss heard definitions of rare words

“If you don’t know word, can you recall anything (e.g., 1st letter)?

Question: Was accuracy greater than chance?

Results: Yes

(Brown, 1991; Brown & McNeill, 1966)

TOT Demo
















In a survey of 51 languages, 45 use tongue metaphor.

On the Tongue

On the Tip of the Tongue

On the Point of the Tongue

On the Head of the Tongue

On the Front of the Tongue

Sparkling at the End of the Tongue (Korean)

(Schwartz, 1999)


1. haiku

2. ellipsis

3. gerrymander

4. palindrome

5. origami

6. marsupials

7. deciduous

8. pterodactyl

9. onomatopoeia

10. kleptomania

11. anemometer

12. omnivore

13. spelunker

1. Three-line verse with 5, 7, and 5 syllables per line

2. the three periods (...) that indicate an omission

3. create odd-shaped voting districts for political benefit

4. word that reads same forward or backward (e.g., tot)

5. Japanese art of paper folding

6. term for mammals with pouches (e.g., kangaroo)

7. tree that sheds leaves every year (unlike evergreens)

8. flying reptile that became extinct

9. word that is pronounced like its meaning (e.g., buzz)

10. mental disorder that causes people to steal

11. instrument used to measure wind speed

12. animal which eats plants and animals

13. person who explores a cave


Demo -

You’ll see 10 word pairs, very quickly.

tree palm

leader king

baseball pitcher

monkey banana

tennis racket

leather saddle

soccer ball

time noon

river bridge

fire hot



For each cue, write target

1. queen

 2. fruit

 3. horse

 4. lunch

 5. stove

 6. wrist

 7. lemonade

 8. noise

 9. dance

 10. cards


Place check by each correct answer

1. queen king

 2. fruit banana

 3. horse saddle

 4. lunch noon

 5. stove hot

 6. wrist palm

 7. lemonade pitcher

 8. noise racket

 9. dance ball

 10. cards bridge

Results: 6 – 10 harder

tree palm  

leader king

baseball pitcher  

monkey banana  

tennis racket

leather saddle

soccer ball

time noon

river bridge

fire hot


encoding specificity

recall improved if study context = test context


Ss study related pairs (strawberry – JAM)

Test includes wrong-context cue (traffic - ?) or no cue

Cue doesn’t help.

Why not? Because words were “encoded” in a “specific” context.

 (Tulving, 1970s)


Internal State Dependence

  • You forget less if your mind or body is in the same state during study and test.
  • Typical Experiment
  • Sad or happy film clip
  • Study phase
  • Delay
  • Sad or happy film clip
  • Test
  • Four groups: sad-sad, sad-happy, happy-sad, happy-happy
  • Results
  • Mood-matched Ss do slightly better on test.

Another Experiment on Internal State Dependence

Ss pedal or sit still on stationary bike while studying and while taking test.


Words recalled at test Test state

pedal still

pedal 6 4

Study state

still 3 7

Practical Implications?

(Miles & Hardman, 1998)


Does chewing vs. not chewing gum produce context effects?

Miles: More work needs to be done…


Miles, C., Charig, R., & Eva, H. (2008). Chewing gum as context: Effects in long-term memory. Journal of Behavioural and Neuroscience Research, Vol. 1 (6), 1-5.

Johnson, A., & Miles, C. (2008). Chewing gum and context-dependent memory: The independent roles of chewing gum and mint flavour. British Journal Of Psychology, 99, 293-306.


Johnson, A. J., & Miles, C. (2007). Evidence against memorial facilitation and context-dependent memory effects through the chewing of gum. Appetite, 48(3), 394-396.

Miles, C., & Johnson, A. J. (2007). Chewing gum and context-dependent memory effects: A re-examination. Appetite, 48(2), 154-158.


External State Dependence we forget less if study environment = test environment

  • Common Claims
  • You should study in the room where you will take the test
  • If you smell odor X while studying, smelling odor X will help you remember
  • Data: Bunk
  • How would you design an experiment to test these claims?


Scuba divers studied a list of words underwater or on pool deck

½ Ss took recall test underwater, and ½ Ss took recall test on pool deck


Test Environment

dry wet

dry 14 9

Study Environment

wet 9 11


In extreme scenarios, matching external states improves recall.

(Godden & Baddeley, 1975)


Drawback of multiple-choice measure


Ss studied 10 words: girl, wall, rope, sign, shoe, head, moon, tree, mass, lion

One week later, Ss took test. “For each question, circle the word you studied earlier.”

1. a. zeal b. lair c. sign d. whim

2. a. rope b. aloe c. clod d. duel


Ss can choose correct answer by eliminating foils (incorrect choices).

Thus, S can exhibit perfect recognition memory without having any memory of words!

Multiple-choice is not a good measure….


Demo – Divide class into 2 groups

1. Who designed first VW?

a) Klein b) Benz c) Speer d) Porsche

2. Who designed first VW?

a) Marconi b) Edison c) Ford d) Porsche


Encoding specificity has been used to improve eyewitness memory

“First recall everything about crime scene. Now …”

(Geiselman et al., 1985)


Another experiment demonstrating encoding specificity

Ss read sentences, and the last word in each sentence was a thing.

For each thing, Ss saw one of two sentences.


½ Ss read "The man lifted the piano." (weight context)

½ Ss read “The man tuned the piano." (music context)

Later, Ss given test: “Try to recall the last word of each sentence.”

During test, Ss received a cue for each word they were trying to recall.


For piano, cue was “something heavy” or “something with a nice sound”

Results: Ss recalled 3 times as much if study context matched test cue.

(Barclay et al., 1974)


“An obvious explanation for this interesting phenomenon is that the reduced rate of memory formation while one is under the influence of the drug protects recently formed memories during a period of time when they are especially vulnerable.” (Wixted, 2005)


October 30, 2005

Dear Abby:

I am engaged to an otherwise great guy I'll call "Wayne," who has a bad habit. He calls me by his ex-wife's name. The first couple of times it happened, I called it a mistake. But now it happens habitually, and I'm at my wit's end.


I've had nightmares about it happening at the altar. I don't think I'd be big enough to forgive that. What do you think?


Canadian toddler Erika Nordby wandered outside at night and nearly froze to death in 2001. She wore only a diaper and T-shirt. It was minus 11 Fahrenheit (-24 Celsius).

When found, her heart had stopped beating for two hours and her body temperature was 61 degrees. She suffered severe frostbite but required no amputations and otherwise recovered.


Interference causes more forgetting when learning material is similar.


Joe takes French (vert-green) and Spanish (verde-green)

Moe takes French (vert-green) and German (grün-green)

French Test: What is French word for green?

Joe suffers more interference than Moe because vert and verde are similar.


Some terminology.

If you learn an association between items (face and name). to pair two items together two items “A-B” and later see “A” and try to recall “B” then

A is the cue and B is the target


You meet fellow student.

Later, you see student and try to recall his or her name.

The face is the cue, and the name is the target.


face-name face - ?


Part 2. learning new memory disrupts consolidation of recently-formed memory


Ss voluntarily take benzodiazepine, which impairs memory for subsequent info.

Groupfirst 5 minnext 5 minlast 5 min

Benzo Ss learn list A take benzo learn list B Test

Placebo Ss learn list A take placebo learn list B Test


Test on List B list: Placebo Ss did better

Benzo impeded subsequent learning (this is just a biology fact)

Test on List A: Benzo Ss did better

Poor learning of list B  more resources for consolidation of list A

(e.g., Fillmore et al., 2001; Hinrichs et al., 1984; Weingartner et al., 1995)


Most common measure of yes-no recognition performance is …

d’ (“d prime”)

a measure of a subject’s ability to discriminate between two kinds of items

(such as old and new faces)

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Students are not responsible for material below 

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

d’ can be found by consulting table or using following formula.

d’ = Z(TP) – Z(FP) where Z(p) = z-score of cumulative area under normal curve

Larger d’ value indicates greater discriminability.

This approach is known as signal detection theory


Other scenarios in which one must make a discrimination.

Is that an enemy bomber or a flock of geese on the radar screen?

Should we hire/admit this applicant?

Is he schizophrenic?

Raise your finger if you hear a beep.

Is the defendant guilty?

Should I reject H0?

Is the man in this photo the same man who robbed you?



Ss saw 50 words during a study session.

Next day: Ss saw test with 50 original words (targets) and 100 new words (foils).

For each word, S asked if he or she recognized it from previous day (“yes” or “no”).

Abby said “yes” to 35 targets and 30 foils.

Beth responded correctly to 30 targets and 60 foils.

Find Abby’s H and FA. H = 35/50 = 70% FA = 30/100 = 30%

Find Beth’s H and FA.H = 30/50 = 60% FA = 40/100 = 40%

By the measure H – FA, who did better? Abby (40%) outscored Beth (20%)