Dr. Mark L. Mitchell


The Three Box Model

How do the boxes differ?

Encoding: Getting the information into a form (code) that the memory will accept. (What forms are acceptable?)

Storage: Keeping information in the box. (how much, how long)

See how long information stays in STM.

Retrieval: Getting the information that is in the box out of the box (how easy/difficult is retrieval)

A video illustrating that chimps have very good visual sensory memory



Why is long term memory important?

LTM's storage is perfect, but there are two problems with LTM:

1. Encoding problems-- Getting information into memory

Examples of encoding problems:

an extreme example of encoding problems: anterograde amnesia (see an example)

See if you have also failed to encode something you've seen many, many times.

2. Retrieval problems--getting information out.

Information is often available, but not accessible

an extreme example of retrieval problems: retrograde amnesia (see an example):

Other (less extreme) examples of retrieval problems:

II. How to get information into LTM

A. Not by Type 1 (maintenance) rehearsal

1. Evidence that Type 1 rehearsal is extremely ineffective:

2. The reason Type 1 rehearsal is ineffective:

(Diagram of Type 1 rehearsal)

B. Properly encode the information by using Type 2 rehearsal.

In Type 2 (also called elaborative) rehearsal, information in STM is changed in one of two ways:

1. Make information m_______

a. Examples of the power of this technique

b. Implications for aging and memory

c. Two ways to take advantage of this technique:



2. V______ information: The power of imagery

Examples, including a mnemonic device

(systematic memory aid) called the method of loci:

    Video of a clever application of the method of loci

By now, you should be able to:

  1. Explain the difference between anterograde amnesia and retrograde amnesia.

  2. Explain the difference between Type 1 and Type 2 rehearsal.

  3. Explain why Type 1 rehearsal doesn't help you get information into LTM.

  4. List the two basic ways of doing Type 2 rehearsal.

  5. Define the term "mnemonic device."

  6. Describe the method of loci.

  7. Explain the difference between an encoding and a retrieval failure.

  8. Explain why Type 2 rehearsal is also called elaborative rehearsal.

  9. Explain the difference between encoding and retrieval.

  10. Explain the difference between accessibility and availability.

  11. Go over a tour of memory

Dr. Mark L. Mitchell

III. Getting information out: Retrieval

A. Examples of retrieval failures (availability [having it] is different from accessibility [getting it out])

1. T.O.T.

2. Recognition is generally easier than recall

3. Saving scores: Relearning is faster than learning it the first time.

B. Why do retrieval failures happen?

Not simply the passing of time (Despite recent attempts to revive it, decay theory is dead!)

Evidence that retrieval failures are not due to time alone:


2. Hypermnesia: better recall over the course of time.

How is hypermnesia possible?

So, time doesn't cause retrieval failure.

However, some retrieval failures are linked to time as Ebbinghaus' forgetting curve illustrates.


* Note an interesting point about shape of the curve:

What are the implications of this shape?

So, if time doesn't cause retrieval failure, why are retrieval failures often linked to time?

Indeed, why do retrieval failures happen at all?

3 reasons:

  1. interference

  2. lack of cues

  3. repression

#1. Interference:

Really a problem when information is s______.

2 types:

Proactive interference: Old (previously learned) information hurts memory for new information.

Group 1 Experiences Proactive Interference
Group 1Learn
List A
List B
Test on
List B
Group 2Learn
List B
Test on
List B

Other examples of proactive interference

Retroactive interference: Newly learned information hurts memory for old information.

Group 1 Experiences Retroactive Interference
Group 1Learn
List A
List B
Test on
List A
Group 2Learn
List A
Test on
List A

Other examples of retroactive interference:

A phenomenon that shows both types of interference

and also shows how passing of time can't account for

forgetting--the serial position curve:

Primacy Recency

Examples to show that the serial position curve occurs often:

Is recall purely a function of time? Evidence?

At what two places is recall best? Implications? Why is it good there?

Where is recall poor? Why would it be so poor there?

#2 Inadequate cues as a cause of retrieval failure

a. Examples of retrieval failures due to lack

of cues

b. The power of physical context in helping retrieval

c. Mental state as a cue: State dependent


#3 Repression (unconsciously motivated forgetting).

Repression can explain:

a. Some cases of retrograde amnesia

b. Childhood amnesia: Poor episodic memory for

childhood (esp. before age 3)

(Click here to learn about a movie that takes advantage of this phenomena)

However, there are at least 3 alternative

explanations for "childhood amnesia"




IV. Review of the material we've covered so far: Mnemonics and why they work

A. Two basic reasons why they work



B. An example of the peg-word mnemonic:

Make pegs---> Link material to pegs---> Find pegs

V. Final thoughts: Is LTM like a library?

Two important similarities:

1. The need to get information into the system

2. The need to have an organized system so that information can be retrieved

Two important differences:

1. Memories, unlike books, may be rewritten every time we "look" at them because memories are reconstructions:

The bad news about reconstruction: Reconstruction can lead to errors, such as

False Memory Syndrome

Why do we reconstruct memories?

Using reconstruction to our advantage

2. Once a book is in the right place and we know how to retrieve it, we can always retrieve it. However, even if we have retrieved information from LTM before, we may not be able to retrieve that material again. Thus, we must engage in overlearning: Studying after you already know it

Why do we need to overlearn?

By now, you should be able to:

  1. Give an example of how information may be available in memory, but not be accessible.

  2. Explain the significance of the fact that information may be available, but not accessible.

  3. Give at least one piece of evidence showing that the decay theory of long term memory is wrong.

  4. List three reasons why retrieval failures occur.

  5. Graph Ebbinghaus's forgetting curve and explain what is (1) discouraging about it and (2) encouraging about it.

  6. Explain the difference between proactive and retroactive interference.

  7. Draw the serial position curve and describe a practical implication of the curve. Then, explain how the curve may be the result of proactive and retroactive interference.

  8. Explain what state dependent learning has to do with cue-dependent forgetting.

  9. Define "childhood amnesia" and give four possible causes of it.

  10. Describe the two basic problems with long term memory and show how the peg word mnemonic allows people to avoid both of those problems.

  11. Explain why similar terms are the most difficult terms to remember.

  12. Explain why the people with the very best memories are those who are most selective about what they try to remember.

  13. Explain why it pays to organize information before putting the information into memory and give at least one example of how to do this.

  14. Have some fun at this site.

  15. Explore the impact of reconstruction and other errors on eyewitness testimony.

  16. Explore mnemonics at this site.

If you would prefer to listen to memory tips, click here to listen to a podcast.

In addition, you could look at the study tips page and see how they make use of the memory strategies we have learned. You should also
 complete the study grid below.

Study Grid: Long Term Memory

Stage of processing What can go wrong?Example(s)How can problems be prevented?
Encoding xxxx xxxx xxxx
Storagexxxx xxxx xxxx
Retrievalxxxx xxxx xxxx

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