Week 7 · Chapter

Chapter 7 — Memory

Introduction to Psychology Free sample edition

The module's primary reading · ~40–50 minutes · Objective 5 (compare the major models of learning and memory and apply them to everyday behavior, including why memory is reconstructive), Objective 3 (describe the biological bases of behavior: neurons and neural transmission, the major neurotransmitters, and the structures and functions of the nervous system and brain) · Read it first this week; the lecture, the slides, the tutorial, the quiz, and the Analysis Workshop all build on it.

In plain language

Memory is how yesterday stays with you: a friend's face, the way to ride a bike, the answer you studied last night. Psychologists break it into three jobs. Encoding is getting information in, storage is keeping it, and retrieval is getting it back out when you need it. This week you will see why a phone number slips away in half a minute, why three short study sessions beat one long one, and why forgetting is steepest in the first hour. You will also learn why a memory you feel sure about can still be wrong, and which parts of the brain each kind of memory leans on.

Why you already care about this

You are in a coffee line and someone waves at you. You know her. She sat two rows ahead of you all last term. Her name is right there, on the tip of your tongue, and it will not come. You smile, say "Hey, you!" and walk off embarrassed. That night, brushing your teeth, the name arrives on its own: Mariana.

The name was never lost. It was stored the whole time. What failed, for a few hours, was getting it back out. That one moment holds most of this chapter. Memory is not one thing that works or breaks. It is a chain of steps, and forgetting can happen at any link.

Psychologists have measured those links for a long time. In 1885, Hermann Ebbinghaus measured his own forgetting with lists of nonsense syllables and found that it was steepest in the first hour. In 1956, George Miller put the span of short-term memory at about 7 items, give or take 2. In 1974, Elizabeth Loftus and John Palmer showed that one word in a question could plant a memory of broken glass that was never there.

By the end of this chapter you will be able to:

name the three processes of memory in order and say which one failed in an everyday slip;
trace information through sensory, short-term, and long-term memory, with the pinned capacity and duration of short-term memory;
use chunking to fit more into working memory, and plan study with deep processing, elaboration, and spacing;
sort a memory as episodic, semantic, or procedural;
read Ebbinghaus's forgetting curve and tell proactive interference from retroactive interference;
explain the misinformation effect from Loftus & Palmer (1974) and why confidence is not accuracy;
match the hippocampus, the amygdala, and the cerebellum to the kinds of memory each supports.

Carry this sentence with you: memory is rebuilt, not replayed.

Where we are

Already covered: Week 1 framed psychology as a science. Week 2 taught operational definitions and experiments, with Ebbinghaus and Loftus & Palmer as models. Week 3 placed the hippocampus and amygdala and introduced H.M. Week 4 showed perception is built. Week 5 linked sleep to memory. Week 6 showed how experience changes behavior.
This week: how experiences are kept, how they fade, and how they change each time you recall them.
How they connect: learning is the change; memory is how the change is kept. And in the same way that Week 4 showed perception is constructed, this week shows memory is reconstructed.
Where we're going next: Week 8 is the midterm review, where you apply the "how do we know?" checklist to Loftus & Palmer and to the sleep and quiz-score data.

You have already met two of this week's studies. In Week 2, Ebbinghaus's percent savings, how much less time relearning takes than first learning, was your model of an operational definition. In the same week, Loftus & Palmer's verb experiment was your model of an experiment, with the verb as the independent variable (IV), the one the researcher manipulates, and the speed estimate as the dependent variable (DV), the one measured. This week you finally learn what those studies found about memory itself. In Week 3 you also met the hippocampus, a structure deep in each temporal lobe that is needed to form new declarative memories. It returns in Section 8.

1. Follow a memory through three processes: encoding, storage, retrieval

Think about a server at a busy restaurant taking an order without a notepad. First, the server has to notice and take in "no onions, dressing on the side." Then the order has to stay in mind while the server walks past three other tables. Last, the server has to pull it back up at the kitchen window. If the meal comes out wrong, the mistake happened at one of those three steps.

Psychologists name the steps this way, always in this order:

Memory is the ability to take in information, keep it over time, and get it back when it is needed; psychologists study it as three processes: encoding, storage, and retrieval.
Encoding is the first process of memory: turning what you sense or think into a form the brain can store, such as noticing a name and linking it to a face.
Storage is the second process of memory: keeping encoded information over time, from a fraction of a second to a lifetime.
Retrieval is the third process of memory: getting stored information back into awareness when you need it, such as recalling an answer during an exam.

With those three in hand, forgetting stops being a mystery word. Forgetting is the inability to retrieve information that was once available, which can come from a failure of encoding, storage, or retrieval.

Worked example — three slips, three processes. Sort each slip by the process that failed.

Amir is introduced to a new coworker while reading a text message. An hour later he has no idea what her name was. He never paid attention to it, so it was never encoded. Encoding failed.
Leilani learned a friend's new apartment number in the spring. By the fall it is gone, and nothing reminds her of it. The stored trace faded. Storage failed.
You cannot name the classmate in the coffee line, but the name arrives that night. The name was stored all along; you could not reach it in the moment. Retrieval failed.

In words: the same "I forgot" can mean three different things, and each one has a different fix.

Misconception check. Students often think forgetting always means a memory was erased. That feels right because the word "forget" sounds like deleting. But the coffee-line name shows the cure: a memory can be stored and still out of reach. Before you say a memory is gone, ask which of the three processes failed.

2. Trace the three-stage model: sensory, short-term, and long-term memory

You are reading on the couch when someone across the room says something. You say, "What?" and then, before they repeat it, you hear the sentence in your head. For a second or two, the sound waited for you. That brief echo is the first stage of memory.

Psychologists map this path in three stages. The three-stage model is the model of memory, proposed by Atkinson and Shiffrin, in which information passes from sensory memory to short-term memory and, if it is rehearsed or encoded, into long-term memory. Each stage has its own size and its own time limit.

Sensory memory is the first stage of memory, which holds a brief, nearly complete copy of what the senses take in for about a second or two before it fades or is passed on.
Short-term memory is the second stage of memory, which holds a small amount of information, about seven items give or take two, for about 15 to 30 seconds unless it is rehearsed.
Long-term memory is the third stage of memory, a relatively permanent store with no known limit on how much it can hold, from which information can later be retrieved.

Attention decides what moves from sensory memory into short-term memory. Rehearsal and encoding decide what moves from short-term memory into long-term memory.

How small is short-term memory? Miller (1956) called it "the magical number seven": a span of 7 ± 2 items. How short is it? Peterson & Peterson (1959) gave people a trio of letters, then made them count backward so they could not rehearse. Recall was about 80% after 3 seconds and about 10% after 18 seconds.

Worked example — two classic numbers, read in words. Put the two pinned findings into plain arithmetic.

Capacity. Miller's 7 ± 2 gives a span of 7 − 2 = 5 to 7 + 2 = 9 items.
Duration. In Peterson & Peterson (1959), recall fell from about 80% to about 10%. That is a drop of about 80 − 10 = 70 points in 18 − 3 = 15 seconds.

In words: short-term memory holds roughly a handful of items, and without rehearsal most of them are gone in well under half a minute. That is why you repeat a parking-garage level out loud on the way to the elevator. An honesty note: Peterson & Peterson's exact curve differs a little from one retelling to the next, so treat 80% and 10% as "about" figures, not precise measurements.

Misconception check. Students often think short-term memory holds information for hours, or that it holds dozens of items. It is tempting because people say "short-term memory" when they mean "what I did this morning." The cure is the pinned numbers: about 7 ± 2 items, for about 15 to 30 seconds without rehearsal. What you did this morning lives in long-term memory.

3. Use working memory: chunking and the limit of about four

Split a dinner bill four ways in your head and notice what you are doing. You hold the total, divide it, keep the answer, and add the tip. You are not storing a number. You are working on it. That is why psychologists now treat short-term memory as a workspace.

Working memory is short-term memory understood as an active workspace, where you hold and manipulate a few pieces of information at once, such as doing mental arithmetic; its capacity is about four chunks, give or take one.

The newer number matters. Cowan (2010) revised the capacity estimate to about 4 ± 1 chunks. That is smaller than Miller's 7, because it counts chunks, not raw items. A chunk is any unit your memory treats as one piece.

Chunking is grouping separate items into larger, meaningful units, such as reading ten digits as three groups, so that more information fits into the limited space of short-term memory.

Worked example — the phone number. Count items, then count chunks.

Cowan's range. About 4 ± 1 chunks gives 4 − 1 = 3 to 4 + 1 = 5 chunks.
As single digits. If you hold a ten-digit phone number as single digits, it is 10 items, more than Cowan's upper limit of 5.
As groups. If you hold it as three groups of 3, 3, and 4 digits, it is 3 chunks, inside the range of 3 to 5.

In words: chunking does not make working memory bigger. It makes each item bigger, so the same small space holds more. The same trick is why a sixteen-digit card number is printed in four groups of four: four chunks fit; sixteen digits do not.

Chunking works best when the groups mean something to you. A nurse who knows drug names can hold a whole medication order as a few chunks. A new hire sees the same order as a long string of letters.

Misconception check. Students often think Miller's 7 and Cowan's 4 contradict each other, so one must be wrong. The cure is to ask what each one counts. Miller counted items in a span task; Cowan counts chunks a person can actively hold while working. Both describe a small, limited space. Cowan's estimate is the modern one, and both are pinned so you can compare them.

4. Encode for keeps: deep processing, elaboration, and spacing

Two roommates study the same twenty vocabulary words for a biology exam. Kalani reads the list aloud ten times. Rafael asks what each word means, links each one to something he already knows, and quizzes himself across three days. A week later, Rafael remembers far more. Both spent effort. Only one spent it on meaning.

Some ways of encoding stick much better than others.

Rote repetition is repeating information over and over without thinking about its meaning; it can hold an item in short-term memory but encodes it weakly for the long term.
Deep processing is encoding that focuses on the meaning of information rather than on its surface features, such as how a word looks or sounds; it produces stronger long-term memories.
Elaborative rehearsal is encoding new information by linking it to its meaning and to things you already know, which makes it more likely to be stored and retrieved later.
The spacing effect is the finding that study spread over several shorter sessions produces better long-term retention than the same amount of study packed into one long session.

Worked example — two study plans with the same total time. Jae-won has 90 minutes to learn the steps of a first-aid course.

Plan A, cramming. One 90-minute session the night before.
Plan B, spacing. Three 30-minute sessions on three different days, and 3 × 30 = 90 minutes, the same total.
Add depth. In each Plan B session, Jae-won explains each step in her own words and connects it to a real situation, such as a cut finger in a kitchen.
Prediction. The spacing effect and deep processing both favor Plan B for the long term, even though the time spent is identical.

In words: you do not need more hours; you need the same hours spread out and spent on meaning. The decision is cheap: book three short sessions instead of one long one.

Misconception check. Students often believe rereading and cramming work best, because the material feels familiar right afterward. That feeling is real, but it measures short-term fluency, not long-term storage. The cure is to test yourself after a gap. If you can explain an idea in your own words days later, it was encoded deeply.

Pause and think. Choose one of these two prompts; they carry equal weight.

(a) Describe how you prepared for a recent test or work training, and name one change, using deep processing or the spacing effect, that would have helped you keep the material longer.
(b) Describe something you remember well years later, such as song lyrics, a recipe, or a sports play, and explain which encoding strategy from this section helped it stick.

5. Sort your memories: explicit memory versus implicit memory

Think about your first day at a job or a new school. You can probably describe where you were and how you felt. You can also state facts, like the capital of a country, without remembering when you learned them. And you can tie a shoelace without being able to explain each finger movement. Those are three different kinds of long-term memory.

Explicit memory is memory a person can consciously recall and put into words, also called declarative memory; it includes episodic memory and semantic memory.
Episodic memory is explicit memory for personal experiences tied to a particular time and place, such as remembering your first day at a new job.
Semantic memory is explicit memory for general facts and knowledge, such as knowing what a word means or which city is a country's capital, without remembering when you learned it.
Implicit memory is memory that shows up in what a person does rather than in what they can consciously recall, also called nondeclarative memory; it includes procedural memory.
Procedural memory is implicit memory for skills and habits, such as riding a bike or typing, that you perform without consciously recalling the steps.

Worked example — one soccer player, three memories. Ifeoma plays midfield on a weekend team. Sort each memory.

She recalls the rainy away game last spring when she scored from a corner kick. It is a personal event with a time and place, so it is episodic.
She knows the offside rule. It is a fact, and she cannot say when she learned it, so it is semantic.
She dribbles past a defender without thinking about her feet. It shows up in what she does, not in what she can say, so it is procedural.

In words: the test is "can you say it, and is it about your own moment?" Say it and it is yours: episodic. Say it but it is general knowledge: semantic. Do it without saying it: procedural.

Misconception check. Students often think a skill like typing is "not really memory" because it does not feel like remembering. The cure is the definition: implicit memory shows up in performance. Your fingers' fluency on a keyboard is a stored memory, even when you cannot name where each key sits.

6. Measure forgetting: the forgetting curve and interference

You study a list of terms on a Monday. How much is left on Tuesday? A week later? Ebbinghaus asked this question about himself in 1885, and he found a clever way to measure even the memory he could no longer recall.

His trick was percent savings. If a list took him 10 minutes to learn the first time and only 6 minutes to relearn later, the relearning saved 4 of the 10 minutes, so savings were 40 percent. A memory you cannot recall can still make relearning faster. Savings catch that hidden memory. That is an operational definition, the exact procedure that turns "how much do I remember?" into a number.

The table below lists Ebbinghaus's results at seven delays.

Ebbinghaus (1885): percent savings on relearning at seven delays after first learning
Delay after learning	Percent savings
19 minutes	58.2%
63 minutes	44.2%
8.8 hours	35.8%
1 day	33.7%
2 days	27.8%
6 days	25.4%
31 days	21.1%

The forgetting curve is the pattern Ebbinghaus measured in which retention drops steeply soon after learning and then levels off, so most forgetting happens early.

Worked example — reading the forgetting curve. Read the table from top to bottom.

Start and end. Savings were 58.2% after 19 minutes and 21.1% after 31 days, a total drop of 58.2 − 21.1 = 37.1 percentage points.
The steep first hour. From 19 minutes to 63 minutes, savings fell from 58.2% to 44.2%, a drop of 58.2 − 44.2 = 14.0 points in 63 − 19 = 44 minutes.
Share of the month's loss. 14.0 ⁄ 37.1 is about 0.38. You can read that as more than a third of the month's forgetting happening in the first 44 minutes.
The flat tail. From 6 days to 31 days, savings fell from 25.4% to 21.1%, a drop of only 25.4 − 21.1 = 4.3 points across 31 − 6 = 25 days.
One day later. Savings were still 33.7% after 1 day. Relearning the list took about one third less time than learning it from scratch, so the forgetting was large but never total.

In words: about 14 points vanished in the first 44 minutes, versus only 4.3 points in the last 25 days, more than a threefold difference packed into a sliver of the time. The decision that follows is about frequency: review new material within a day, while more of it is still there, rather than waiting a week. A caveat: Ebbinghaus tested one person, himself, on meaningless syllables, so meaningful material usually fades more slowly. The shape, steep then flat, is the part that has held up.

Why does memory fade? Two causes are familiar from Section 1. Encoding failure is forgetting that happens because information never made it into long-term memory in the first place, such as not being able to describe a coin you have handled many times. Retrieval failure is forgetting in which information is stored but cannot be reached at the moment it is needed, such as a name on the tip of your tongue. The classmate's name in the coffee line was a retrieval failure, not a lost memory.

A third cause is other memories getting in the way. Interference runs in both directions, and the direction is the whole point.

Proactive interference is forgetting in which older learning gets in the way of recalling newer learning, such as writing an old phone number when you try to give your new one.
Retroactive interference is forgetting in which newer learning gets in the way of recalling older learning, such as being unable to recall an old locker combination after learning this year's.

A memory hook for the direction: pro means forward, so old learning pushes forward into the new; retro means backward, so new learning reaches back into the old.

Worked example — two locker combinations. Tomás used one gym locker combination all last year. This year he has a new one.

In the first week, he keeps spinning last year's numbers. The old learning is blocking the new. That is proactive interference.
In the spring, a friend asks for last year's combination, and Tomás can only think of this year's. The new learning is blocking the old. That is retroactive interference.

Misconception check. Students often swap proactive and retroactive interference. The swap is tempting because both names describe "memories colliding." The cure is to ask which memory you are trying to retrieve. If you want the new one and the old one intrudes, it is proactive. If you want the old one and the new one intrudes, it is retroactive.

7. Rebuild, don't replay: reconstructive memory and the misinformation effect

Ask two friends to describe the same concert a year later. Both will be sure. Their stories will not match. Each one fills gaps with what usually happens at concerts, what they heard afterward, and what they believe now. Neither is lying. Both are rebuilding.

Reconstructive memory is the idea that recall rebuilds a memory from stored pieces, expectations, and later information each time, rather than replaying an exact recording.

Loftus & Palmer (1974) showed how far the rebuilding can go. Students watched films of car accidents. Then they answered a question about how fast the cars were going when they "smashed," "collided," "bumped," "hit," or "contacted" each other.

Worked example — the verb and the memory. Walk through the two experiments in order.

The design. In Loftus & Palmer (1974) Experiment 1, the verb in the question was the independent variable (IV). The speed estimate was the dependent variable (DV).
The estimates. "Smashed" averaged 40.8 mph and "contacted" averaged 31.8 mph, a gap of 40.8 − 31.8 = 9.0 mph. Same films, different word.
The false memory. A week later in Experiment 2, 16 ⁄ 50 = 32% of the "smashed" group reported broken glass that was never in the film, against 7 ⁄ 50 = 14% for "hit" and 6 ⁄ 50 = 12% for the control group asked no speed question.
Compare. That is 32 − 12 = 20 points above the control group, or about one student in three in the "smashed" group.
What the design may conclude. Participants were randomly assigned to a verb, so the verb was the only planned difference between the groups. That lets you say the wording of a question changed what people later remembered.

In words: about one in three students who heard "smashed" remembered glass that was not there, versus about one in eight who were asked no speed question. That is why a careful police interviewer chooses neutral wording on purpose.

The misinformation effect is the finding that misleading information supplied after an event, such as the wording of a question, can change what a person later remembers about the event.

The same rebuilding happens to memories that feel unshakable. A flashbulb memory is a vivid, detailed memory of the moment a person learned about a surprising, emotional event; it feels exact and is held with confidence, but it can change over time like any other memory. You may remember exactly where you were when you heard big news. That vividness is real. It is not a guarantee.

Carry the rule: confidence is a feeling, not a fact-check.

Misconception check. Students often believe that a vivid, confident memory must be an accurate one. It is tempting because detail and certainty feel like proof. The cure is the broken glass: students in Loftus & Palmer (1974) reported a detail that was never in the film. Confidence tells you how a memory feels, not whether it matches what happened. That is why an eyewitness's certainty alone should never settle a case.

Pause and think. Choose one of these two prompts; they carry equal weight.

(a) Describe a time you and someone else remembered the same event differently, such as a family trip or a game, and explain the difference with reconstructive memory.
(b) Write two versions of a question about a minor kitchen accident, one neutral and one leading, and explain which word in the leading version could change a witness's memory.

8. Locate memory in the brain: hippocampus, amygdala, cerebellum, and H.M.

Picture a cyclist who nearly gets hit by a car turning without signaling. Years later she still remembers the moment in sharp detail, and she still brakes smoothly on that same corner without thinking about it. Different parts of her brain hold different parts of that day.

You met three structures in Week 3. Here is how each one supports memory:

The hippocampus, a structure deep in each temporal lobe, is needed to form new declarative memories, the facts and events a person can consciously recall. In this week's terms, it is needed to form new explicit memories.
The amygdala, also deep in each temporal lobe, is central to fear and strengthens memories carrying emotional weight. That is part of why the near-miss feels so vivid.
The cerebellum, at the back of the brain below the lobes, coordinates movement and balance and supports learning motor skills. That makes it part of procedural memory, such as the smooth braking she no longer thinks about.

The case of H.M. (Scoville & Milner, 1957) shows, in one person, that forming new explicit memories and learning new motor skills rely on different systems. To control seizures, surgeons removed much of the medial temporal lobe on both sides of his brain, including much of both hippocampi. Afterward, he could no longer form new declarative memories. He kept most memories from before the operation, and he could still learn new motor skills.

Worked example — reading H.M. with this week's terms. Sort his three outcomes.

New facts and events. He could not form new declarative memories, so explicit memory for anything new failed. The hippocampus was needed for that.
Old memories. He kept most memories from before the operation, so long-term storage of older memories did not depend on those structures in the same way.
New skills. He could still learn new motor skills, so procedural memory, which leans on the cerebellum, still worked.

In words: losing the hippocampus took away the ability to make new explicit memories, not memory as a whole. A limitation to keep in mind: H.M. is a case study, one person studied in depth. Week 2 taught you that a case study can suggest an idea but cannot show it holds for everyone, which is why researchers tested these links in many more people afterward.

Misconception check. Students often think the hippocampus is "where all memories are stored," or that H.M. lost his whole memory. The cure is H.M.'s own pattern: old memories stayed, new skills could still be learned, and only new explicit memories failed. Write "the hippocampus is needed to form new explicit memories," not "memories live in the hippocampus."

Key terms

Memory — The ability to take in information, keep it over time, and get it back when it is needed; psychologists study it as three processes: encoding, storage, and retrieval. (first used: 1. Follow a memory through three processes: encoding, storage, retrieval)
Encoding — The first process of memory: turning what you sense or think into a form the brain can store, such as noticing a name and linking it to a face. (first used: 1. Follow a memory through three processes: encoding, storage, retrieval)
Storage — The second process of memory: keeping encoded information over time, from a fraction of a second to a lifetime. (first used: 1. Follow a memory through three processes: encoding, storage, retrieval)
Retrieval — The third process of memory: getting stored information back into awareness when you need it, such as recalling an answer during an exam. (first used: 1. Follow a memory through three processes: encoding, storage, retrieval)
Forgetting — The inability to retrieve information that was once available, which can come from a failure of encoding, storage, or retrieval. (first used: 1. Follow a memory through three processes: encoding, storage, retrieval)
Three-stage model — The model of memory, proposed by Atkinson and Shiffrin, in which information passes from sensory memory to short-term memory and, if it is rehearsed or encoded, into long-term memory. (first used: 2. Trace the three-stage model: sensory, short-term, and long-term memory)
Sensory memory — The first stage of memory, which holds a brief, nearly complete copy of what the senses take in for about a second or two before it fades or is passed on. (first used: 2. Trace the three-stage model: sensory, short-term, and long-term memory)
Short-term memory — The second stage of memory, which holds a small amount of information, about seven items give or take two, for about 15 to 30 seconds unless it is rehearsed. (first used: 2. Trace the three-stage model: sensory, short-term, and long-term memory)
Long-term memory — The third stage of memory, a relatively permanent store with no known limit on how much it can hold, from which information can later be retrieved. (first used: 2. Trace the three-stage model: sensory, short-term, and long-term memory)
Working memory — Short-term memory understood as an active workspace, where you hold and manipulate a few pieces of information at once, such as doing mental arithmetic; its capacity is about four chunks, give or take one. (first used: 3. Use working memory: chunking and the limit of about four)
Chunking — Grouping separate items into larger, meaningful units, such as reading ten digits as three groups, so that more information fits into the limited space of short-term memory. (first used: 3. Use working memory: chunking and the limit of about four)
Rote repetition — Repeating information over and over without thinking about its meaning; it can hold an item in short-term memory but encodes it weakly for the long term. (first used: 4. Encode for keeps: deep processing, elaboration, and spacing)
Deep processing — Encoding that focuses on the meaning of information rather than on its surface features, such as how a word looks or sounds; it produces stronger long-term memories. (first used: 4. Encode for keeps: deep processing, elaboration, and spacing)
Elaborative rehearsal — Encoding new information by linking it to its meaning and to things you already know, which makes it more likely to be stored and retrieved later. (first used: 4. Encode for keeps: deep processing, elaboration, and spacing)
Spacing effect — The finding that study spread over several shorter sessions produces better long-term retention than the same amount of study packed into one long session. (first used: 4. Encode for keeps: deep processing, elaboration, and spacing)
Explicit memory — Memory a person can consciously recall and put into words, also called declarative memory; it includes episodic memory and semantic memory. (first used: 5. Sort your memories: explicit memory versus implicit memory)
Episodic memory — Explicit memory for personal experiences tied to a particular time and place, such as remembering your first day at a new job. (first used: 5. Sort your memories: explicit memory versus implicit memory)
Semantic memory — Explicit memory for general facts and knowledge, such as knowing what a word means or which city is a country's capital, without remembering when you learned it. (first used: 5. Sort your memories: explicit memory versus implicit memory)
Implicit memory — Memory that shows up in what a person does rather than in what they can consciously recall, also called nondeclarative memory; it includes procedural memory. (first used: 5. Sort your memories: explicit memory versus implicit memory)
Procedural memory — Implicit memory for skills and habits, such as riding a bike or typing, that you perform without consciously recalling the steps. (first used: 5. Sort your memories: explicit memory versus implicit memory)
Forgetting curve — The pattern Ebbinghaus measured in which retention drops steeply soon after learning and then levels off, so most forgetting happens early. (first used: 6. Measure forgetting: the forgetting curve and interference)
Encoding failure — Forgetting that happens because information never made it into long-term memory in the first place, such as not being able to describe a coin you have handled many times. (first used: 6. Measure forgetting: the forgetting curve and interference)
Retrieval failure — Forgetting in which information is stored but cannot be reached at the moment it is needed, such as a name on the tip of your tongue. (first used: 6. Measure forgetting: the forgetting curve and interference)
Proactive interference — Forgetting in which older learning gets in the way of recalling newer learning, such as writing an old phone number when you try to give your new one. (first used: 6. Measure forgetting: the forgetting curve and interference)
Retroactive interference — Forgetting in which newer learning gets in the way of recalling older learning, such as being unable to recall an old locker combination after learning this year's. (first used: 6. Measure forgetting: the forgetting curve and interference)
Reconstructive memory — The idea that recall rebuilds a memory from stored pieces, expectations, and later information each time, rather than replaying an exact recording. (first used: 7. Rebuild, don't replay: reconstructive memory and the misinformation effect)
Misinformation effect — The finding that misleading information supplied after an event, such as the wording of a question, can change what a person later remembers about the event. (first used: 7. Rebuild, don't replay: reconstructive memory and the misinformation effect)
Flashbulb memory — A vivid, detailed memory of the moment a person learned about a surprising, emotional event; it feels exact and is held with confidence, but it can change over time like any other memory. (first used: 7. Rebuild, don't replay: reconstructive memory and the misinformation effect)

Summary

Memory runs in order: encoding, storage, retrieval; forgetting is a failure at any step.
Sensory memory lasts a second or two; short-term memory holds about 7 ± 2 items for about 15 to 30 seconds.
Working memory is an active workspace of about 4 ± 1 chunks, and chunking fits more into it.
Deep processing, elaboration, and spacing beat rote repetition and cramming.
Explicit memory is episodic or semantic; implicit memory includes procedural skills.
The forgetting curve drops steeply in the first hour, then levels off.
Proactive interference: old blocks new. Retroactive interference: new blocks old.
Memory is rebuilt, not replayed; a leading question can plant a false detail.
Confidence is not accuracy, even for a flashbulb memory.
The hippocampus forms new explicit memories, the amygdala strengthens emotional ones, and the cerebellum supports skills.
Ebbinghaus's percent savings is an operational definition; Loftus & Palmer's random assignment is what earns the word "cause."

Check your understanding

Work these before looking at the answers — they are ungraded, and the answers (with reasoning) are at the bottom of the page.

A cashier's store switches to a new register system with new item codes. For the first two weeks, she keeps typing the old codes. Which kind of interference is this, and how do you know the direction?
A gym assigns members a twelve-digit membership number. Yusuf memorizes it as four groups of three digits. How many chunks is that, and does it fit Cowan's range of about 4 ± 1 chunks?
Bao has six hours to prepare for a commercial driving permit test. They can study for six hours on one day, or for one hour on each of six days. Which plan does the spacing effect favor, and is the total study time the same?
After a minor fender-bender in a parking lot, an insurance agent asks a witness, "Did you see the car speed through the lot?" Why might that question change what the witness remembers, and what would a better question be?

Answers (worked reasoning — read after attempting)

Proactive interference. She is trying to retrieve the new codes, and the old codes intrude. Older learning is getting in the way of newer learning, so the interference runs forward. If, months later, she could not recall an old code because the new ones kept coming to mind, that would be retroactive.
Four chunks. Twelve digits split into groups of three gives 12 ÷ 3 = 4 groups. Cowan's range is 4 − 1 = 3 to 4 + 1 = 5 chunks, so 4 fits inside it. As twelve single digits, the number would be far above the range.
The spaced plan. One hour on each of six days is 6 × 1 = 6 hours, the same total as the single six-hour day. The spacing effect says study spread over several shorter sessions produces better long-term retention than the same amount packed into one session, so the six short sessions should win.
The word "speed" supplies information after the event. By the misinformation effect, it can change what the witness later remembers, perhaps adding speed that was not there, the same way "smashed" added broken glass in Loftus & Palmer (1974). A better question is neutral: "What did you see the car do in the lot?"

Next up in this module: the Readings & Resources page, the lecture tutorial, the practice set, and the quiz — and next week the "how do we know?" checklist, a three-question method, runs on Loftus & Palmer.

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