Dr. Mark L. Mitchell


The Three Box Model


The boxes (memories) differ in terms of

Encoding: Getting information into the box (putting the information in a code that the memory will accept)

Storage: Keeping information in the box (how much can be kept-- and for how long?)

Retrieval: Getting the information out of the box (how able are we to access what is in memory?)

Short quiz on the basics of memory

Sensory Memory

A video illustrating that chimps have very good visual sensory memory

Drag and drop matching game to test your knowledge of Sensory Memory  

We take our sensory memory for sound (our echoic memory) for granted when it comes to helping us understand what others are saying. 
To appreciate that we do rely on our limited sensory memory to process speech, play this audio file--it has been slowed down so much that you can't rely on your
sensory memory to keep the sounds of individual words in memory. As a result, it is hard to understand.

Here is the same sentence at regular speed. It is, thanks to your echoic memory, easy to understand.

Short term memory

See how long information stays in STM.

An example of how criminals take advantage of the limits of short term memory (and yet another example of the limits of multitasking)

A fictional but humorous example of the problem of having an extremely limited STM (from Monty Python)

A short quiz on short term memory

See if you can tell the difference between short term and sensory memory

Compare the speed of decay from Sensory Memory to the speed of decay from Short Term Memory


Why is long term memory important?

    Without our episodic long term memory, we would live only in the present (plus the few seconds that short term memory would buy us). To see how challenging

that would be, consider the case of Clive Wearing, a man without the ability to form episodic long term memories)

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

1. Encoding problems-- Getting information into memory

Examples of encoding problems:

    If a person cannot form any new declarative memories, that person has an extremely rare condition called  anterograde amnesia. Two well-known cases of this condition are

              The case of HM (note the difference between declarative and procedural memory, as well as between STM and LTM)

              The case of Clive Wearing, that was linked to above. If you don't remember, you weren't paying attention -- or maybe you have anterograde amnesia.

                * If you want to get a sense of anterograde amnesia through a fictional account, you can watch the following episode of NBC's "The Blacklist"

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

    Where is the nearest fire alarm to your classroom?

      See the surprising thing that college students don't know about Apple

*Note that just as jello and concrete need time to set, so do memories. The process of a memory solidifying is called consolidation.  One implication of consolidation is that your memory will  benefit by taking a 15 minute break after learning information. Another implication of the need to let memories set is that getting enough sleep is very important for being able to remember information.

2. Retrieval problems--getting information out.

Information is often available in long term memory (it is in the box), but not accessible (you can't get it out of the box at this moment).

Common examples

        You can recognize the names of the 7 dwarfs, but you probably can't name them.

    The tip of the tongue phenomena, in which you can't come up with a name or word but you know you know it.

an extreme example of retrieval problems: retrograde amnesia

II. How to get information into LTM

A. Not by Type 1 (maintenance) rehearsal: things over and over.


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
attempt number

a. Examples of the power of this technique

b. Implications for aging and memory: As you get older, memory could improve because it is easier to make information meaningful. That is, you have more old information to which you can link new information. This humorous video shows a young girl having trouble remembering a telephone message because she cannot link the information to something she already knows.

c. Two ways to take advantage of this technique:

1.Come up with your own

Attempt number

2. As how the new information is to what you have already learned.

Attempt number

2. Make the information
attempts =

Examples, including a mnemonic device

(systematic memory aid) called the method of loci:

    Video of a clever application of the method of loci

See how a guy went from having an average memory to being a memory world champion in less than one year.

By now, you should be able to:
  1. Match memories to their characteristics using this interactive table.
  2. Explain the difference between anterograde amnesia and retrograde amnesia.
  3. Explain the difference between Type 1 and Type 2 rehearsal.
  4. Explain why Type 1 rehearsal doesn't help you get information into LTM.
  5. List the two basic ways of doing Type 2 rehearsal.
  6. Define the term "mnemonic device."
  7. Describe the method of loci.
  8. Explain the difference between an encoding and a retrieval failure.
  9. Explain why Type 2 rehearsal is also called elaborative rehearsal.
  10. Explain the difference between encoding and retrieval.
  11. Explain the difference between accessibility and availability.

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. The Tip Of the Tongue (TOT)phenomena discussed earlier

2. Recognition is generally easier than recall (as dicussed earlier, it is easier for you to recognize the names of the 7 dwarfs than it is for you to recall all 7.

3. Saving scores: Relearning is faster than learning it the first time. So, if you could remember only 2 of the 7 dwarfs, it would be easy for you to relearn the other 5. Similarly, even if it seemed that you "forgot" everything you learned in a course, it would be much easier for you  to relearn that information than it had been to learn it the first time. In advanced courses, you will probably quickly relearn what you learned in previous courses.

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:

1. People can have great memories for past events

2. Hypermnesia: better recall over the course of time. Hypermnesia is possible because some of the "forgotten" information doesn't go away; it is just hard to find. If you keep looking, you can find much of that information.

So, time alone doesn't cause retrieval failures.

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

Ebbinghaus Forgetting Curve
From Nheise at English Wikibooks through a GNU Free Documentation License 1.2 via Wikimedia Commons  

* Note that the curve is not a straight line--forgetting levels off.

  1. What bad news about memory does the forgetting curve reveal?
  2. What good news about memory does the forgetting curve reveal?
  3. Does the forgetting curve support or go against the idea that we should have year round schools to prevent the forgetting that occurs over the long summer vacation?

But if time doesn't cause retrieval failures (as suggested by hypermnesia and people having good memories for long ago events), why are retrieval failures often linked to time (as shown by the forgetting curve) ? To answer that question, let's first ask 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
Attempt number

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

Think of other examples of proactive interference (Hints: Has this happened when a friend changed phone numbers? Have previous misconceptions you had about how memory works acted to  interfere with your recall of the newer information you have learned about memory? Will learning about proactive interference hurt your ability to learn about retroactive 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

Will the act of learning about retroactive interference recently act to interfere with your memory of proactive interference?

Practice distinguishing proactive interference from 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:

Serial position

Graph Courtesy of Creative Commons License 3.0 via Wikimedia Commons

If you look at the serial position curve, can you say that recall gets worse over time?

At what two places is recall best? Implications? How could interference explain why recall is good in those two places?

Where is recall poor? How could interference explain why recall is so poor there?


Look at some terms that you might have trouble remembering because of interference

#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 learning (also called state dependent memory)

#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 Foundation Website

A true story of false memory (4 minute video)

Innocent people "remembering" being murderers (fascinating magazine article)

Therapists causing false memories (3 minute video from Penn and Teller)

Your first "memory" may be a false memory (short blog entry)

Four-minute video summarizing one of the first experiments to demonstrate that memories can be reconstructed incorrectly false memory (We recommend muting the sound)

If you want to read a fascinating autobiography in which false memories play a role,  borrow or buy Tara Westover's best selling book: "Educated."

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. Master this interactive outline.
  15. Have some fun at this site.

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

  17. Explore mnemonics at this site.
  18. Take this short memory quiz

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 x



xxxx xxxx



xxxx xxxx



xxxx xxxx

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