If you were trying to help another student improve his study skills, what ideas from this chapter would you suggest?

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Human Memory

It is good to have an end to journey towards; but it is the journey that matters, in the end.

Ursula K. Le Gui

http://www.wnyc.org/shows/radiolab/episodes/2007/06/08

Stage theory of memory
Assumes humans have 3-stage
Memory

Process by which information is:
Recording
Encoding
Stored in the brain
Storage
Later retrieved
Retrieval
Eventually (possibly) forgotten

Our memory is the process by which information is retained for later use. The basic process by which information is processed follows this format: information is acquired and encoded, which leads to storage in the brain, which leads to the possibility of later retrieval (though as you know at test time, is not a guarantee), and the possibility of eventually forgetting the information.

Today, cognitive psychologists like to compare the human mind to a computer and memory to an information-processing system. I think you can appreciate the analogy. Your PC acquires (or receives) input from a keyboard or a mouse; it converts the symbols into a special numeric code; it saves the information on a hard drive, CD, or disk; it then retrieves the data from the disk to be displayed on a screen or sends it to a printer. If the computer crashes, if there’s not enough space on the disk, if the file was deleted, or if you enter the wrong retrieval command, the information becomes inaccessible, or ‘forgotten’.

Three-System Approach to Memory

Sensory information

economics

history

religion

culture

science

literature

Information is taken into brain

Information gets processed, analyzed, and stored until use

RETRIEVAL

Information is used as basis of behaviors and interactions

INPUT

math

STORAGE

Three-System Approach to Memory

Three types of memory
Sensory memory
Only an instant
Short-term memory (STM)
15-25 seconds
Long-term memory (LTM)
Can hold vast quantities of information and relatively permanent

Using the computer as a model, memory researchers seek to trace the flow of information as it is mental processed. In this Three-System Approach to Memory, a stimulus that registers on our senses can be remembered only if it 1. Draws attention, which brings it into consciousness; 2. Is encoded, or transferred to storage sites in the brain, and 3. Is retrieved for use at a later time.

Within this information-processing memory approach, three types of memory have been distinguished: sensory, short-term and long-term. Sensory memory stores all stimuli that register on the senses, holding literal copies for a brief moment ranging from a fraction of a second to four seconds usually less. Sensations that do not draw attention tend to vanish, but those we ‘notice’ are transferred to short-term memory , another temporary storage system that can hold seven or so items of information for about 20 seconds, less than 1 minute. Although STM fades quickly, information can be held for a longer period of time through repetition and rehearsa or chunkingl. When people talk about attention span, they are referring to short-term memory.

Finally, long-term memory is a somewhat permanent storage system that can hold vast quantities of information for many years. Science writer Isaac Asimov once estimated that LTM takes in a quadrillion separate bits of information in the course of a lifetime. Mathematician John Griffith estimated that, from birth to death, the average person stores five hundred times more information than the Encyclopedia Britannica. When people talk about memory, long-term memory is typically what they have in mind.

We’ll talk about each of these in a little more detail later on.

Information-Processing Model of Memory

Short-term

memory

Stimulus

Sensory

memory

Long-term

memory

Attention

Encoding

Retrieval

Forgetting

Many events register in sensory memory. Those that are noticed are briefly stored in short-term memory; those that are encoded are transferred to a more permanent facility. As shown forgetting may be caused by failures of attention, encoding, or retrieval.

Note, however, that this is only a model and does NOT mean that the brain has three separate storage bins. This is only one view of how memory works. There is a radically different view. Most computers process instructions in fixed sequence, one linear step at a time. In contrast, the human brain performs multiple operations simultaneously, ‘in parallel’. Thus, some cognitive psychologists have rejected the information-processing model in favor of parallel-processing models in which knowledge is represented in a web-like network of connections among thousands of interacting ‘processing units’ all active at once.

The two main questions we’ll be asking ourselves throughout this chapter are: How are memories stored? And to what extend are our memories of the past faithful to reality?

Sensory Memory

Two types
Iconic memory
Visual
Lasts less than a sec
Sperling’s tests (1960s)
Echoic memory
Auditory
Fades within 2-3 sec

Sensory

Input

Sensory

Memory

Take a flashlight into a dark room, turn it on, shine it on a wall, and wave it quickly in a circular motion. What do you see? If you twirl it fast enough, the light will appear to leave a glowing trail, and you’ll see a continuous circle. The reason: Even though the light illuminates only one point in the circle at a time, your visual system stores a ‘snapshot’ of watch point as you watch the next point. The visual image is called an icon, and the snapshot it stores is called iconic memory.

People typically don’t realize that a fleeting mental trace lingers after a stimulus is removed from view. Nor did cognitive psychologists realize it until George Sperling’s ingenious series of experiments.

Sperling’s Experiment

Presented matrix of letters for 1/20 seconds
Report as many letters as possible
Subjects recalled only half of the letters
Was this because subjects didn’t have enough time to view entire matrix?
No
How did Sperling know this?

Sperling instructed subjects to stare at the center of a blank screen. Then he flashed an array of the letters for 1/20 of a second and asked subjects to name as many of the letters as possible. Try it for yourself. You’ll probably recall about a a handful of letters. In fact, Sperling found that no matter how large the array was, subjects could name only four or five items. Why? One possibility is that people can register just so much visual input in a single glance – that twelve letters is too much to see in so little time. A second possibility is that all letters registered by the image faded before subjects could report them all. Indeed, many subjects insisted that they were able to ‘see’ the whole array but then forgot some of the letters before they could name them.

Did the information that was lost leave a momentary trace, as subjects had claimed, or did it never register in the first place? To test these alternative hypotheses, Sperling devised the ‘partial-report technique’. Instead of asking subjects to list all the letters, he asked them to name only one row in each array – a row that was not determined until after the array was shown. In this procedure, each presentation was immediately followed by a tone signaling which letters to name: A high-pitched tone indicated the top line; a medium pitch, the middle line; a low pitch, the bottom line.

If the tone was presented very soon the participants would recall most of the letters in the indicated row. But if the delay was more than one quarter of a second, the participants recalled an average of just over one letter per row, indicating how quickly information is lost in the sensory register.

Sperling’s Iconic Memory Experiment

Sperling’s Experiment

Recall was almost perfect
Memory for images fades after 1/4 seconds or so, making report of entire display hard to do

http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=dcr::640::480::/sites/dl/free/0073370207/25025/ICONIC.dcr::Iconic Memory

http://www.mhhe.com/feldmaness8e

High

Medium

Low

If the saw the entire array, subjects should have been able to report all the letters in a prompted row correctly – regardless of which row was prompted. Sperling was right: subjects correctly recalled 3 letters per row. In other words, all 9 letters, not 4 or 5, were instantly registered in consciousness before fading, held briefly in iconic memory.

To determine how long this type of memory lasts, Sperling next varied the time between the letters and the tone that signaled the row to be recalled. He found that the visual image started to fade as the interval was increased to ¼ of a second. Since this study, researchers have found when it comes to pictures of objects or scenes, words, sentences, and other visual stimuli briefly presented, people form ‘fleeting memories’ that last for just a fraction of a second.

Not an afterimage because Sperling showed he could present the letters to one eye and influence the memory by presenting a bright flash to the other eye. This would not have worked if the visual information was stored on the retina.

Sensory Memory

Why do we need sensory memory?

A similar phenomenon exists for auditory stimuli. The next time you listen to the radio, notice after you turn it off how an ‘echo’ of the sound seems to reverberate inside your head. This auditory sensory register is called echoic memory. Just how much auditory input is stored in echoic memory? In a study modeled after Sperling’s, Christopher Darwin and others (1972) put headphones on subjects and all at once played three sets of spoken letters – in the right ear, in the left ear, and in both ears at once. Subjects then received a visual signal indicating which set to report. Using this study and others, researchers have found that echoic memory holds only a few items but lasts for two or three seconds, and perhaps even longer, before activation in the auditory cortex fades.

Whether a sensory memory system stores information for one-third of a second or for three seconds, you might wonder: What’s the point of having a ‘memory’ that is so quick to decay? To answer this question, try to imagine what your perceptions of the world would be like without sensory memories. Without the visual icon, for instance, you would lose track of what you see with every blink of the eye – as if you were viewing the world through a series of snapshots rather than on a continuous film. Similarly, it would be hard to understand spoken language without the persistent traces of echoic memory. Speech would be heard as a series of staccato sounds rather than as connected words and phrases. In fact, we have other sensory memories as well – for touch, smell, and taste stimuli.

Short-term Memory

Conscious processing of information
Attention is the key
Limits what info comes under the spotlight of short-term memory at any given time
Limited capacity
Can hold 7 ± 2 items for about 20 seconds

AKA working memory

Working or

Short-term

Memory

Sensory

Input

Sensory

Memory

Attention

Think about what your environment is like as you walk from class to class on campus. You’re seeing people, trees, buildings, trash. You’re hearing multitudes of conversations, the sounds of cars as they drive past, the sounds of leaves as they fall. You’re smelling the car exhaust, the perfume of the girl next to you, the flowers that are blooming, and a pungent trash can that you walk past. More stimuli is probably reaching your sensors than you can think or write about, but most never reach your consciousness and are immediately ‘forgotten’. The key is attention. As we talked about earlier, sensations that do not capture our attention quickly tend to evaporate, whereas those we notice are transferred to short-term memory – a somewhat more lasting but limited storage facility. As we saw in the ‘Sensation and Perception’ chapter, people are selective in their perceptions and can instantly direct their attention to stimuli that are interesting, adaptive, or important.

From the sensory register, the brain encodes information – that is, it converts it into a form that can be stored in short-term memory. A stimulus may be encoded in different ways. After you read a sentence from a book, you might recall a picture of the letters and their placement on the page (visual encoding), the sounds of the words themselves (acoustic encoding), or the meaning of the sentence as a whole (semantic encoding). Research shows that people typically encode this type of information in acoustic terms. Thus, when subjects are presented with a string of letters and immediately asked to recall them, the make more ‘sound-alike’ errors than ‘look-alike’ errors. For example, subjects mis-recall an ‘F’ as an ‘S’ or ‘X’, but not as an ‘E’ or ‘B’. Subjects are also more likely to confuse words that sounds alike (man, can) than words that are similar in meaning (big, huge) – further indicating that we tend to encode verbal information in acoustic terms rather than in semantic terms.

Memorize the following list of numbers:

1 8 1 2 1 9 4 1 1 7 7 6 1 4 9 2 2 0 0 1

Write down the numbers in order.

Now, try again…

1812 1941 1776 1492 2001

Demonstration

Attend to the words in the green box as they flash on the screen. When the last word disappears, write down as many words as you can recall.

CAT

BREAD

DOOR

HAT

TABLE

FOOT

DOG

SON

SNOW

BUS

END

Cat, Bread, Door, Hat, Table, Foot, Dog, Son, Snow, Bus

Accuracy of recall for a single group of three consonants declines rapidly when subjects are prevented from rehearsing by being asked to count backwards

Percent of accuracy of recall

100

Interval before recall in seconds

Test your memory

Do you remember what a penny looks like?

Long-term memory - Encoding

Rehearsal
Elaborative rehearsal

Levels of processing
Semantic (meaning) is more effective than visual or acoustic processing

Self-referent effect
By viewing new info as relevant to the self, we consider that info more fully and are better able to recall it

Do you remember your fourth birthday, the name of your first-grade teacher, or the smell of floor wax in the corridors of your elementary school? Can you describe a dream that you had last night or recite the words of the national anthem? To answer these questions, you would have to retrieve information from the mental warehouse of long-term memory. Like the hard drive on a computer, long-term memory is a relatively enduring storage system that has the capacity to retain vast amounts of information for long periods of time. We’ll examine long-term memories of the recent and remote past – how they are encoded, stored, retrieved, forgotten, and even reconstructed in the course of a lifetime.

Information can be kept alive in short-term working memory by rote repetition or maintenance rehearsal. But to transfer something into long-term memory, you would find it much more effective to use elaborative rehearsal – a strategy that involves thinking about the material in a more meaningful way and associating it with other knowledge that is already in long-term memory. The more deeply you process something, the more likely you are to recall it at a later time.

To demonstrate this process, Craik & Tulving (1975) showed a subject a list of words, one at a time, and for each asked them for 1) a simple visual judgment that required no thought about the words themselves (Is the word printed in capital letters?); 2) an acoustic judgment that required subjects to at least pronounce the letters as words (Does the word rhyme with smell?); or 3) a more complex semantic judgment that compelled subjects to think about the meaning of the words (Does the word fit the sentence ‘I saw a blank in the pond’?). Subjects did not realize that their memory would be tested later. Yet words that were processed at a ‘deep’ level, in terms of meaning, were more easily recognized than those processed at a ‘shallow’ level.

Does making complex semantic judgments, compared to simple visual judgments, activate different regions of the brain? Is it possible to see physical traces of deep processing? Using functional MRI technology, researchers devised a study similar to the Craik & Tulving study where subjects were shown stimulus words on a computer and were instructed to determine whether the words were concrete or abstract (a semantic judgment) or simply whether they were printed in uppercase or lowercase letters (a visual judgment). As in past research, subjects later recalled more words for which they made semantic rather than visual judgments. In addition, however, the brain-imaging measures showed that processing the words in semantic terms triggered more activity in a part of the frontal cortex of the language-dominant left hemisphere.

Perhaps the most effective form of elaborative rehearsal is the linking of new information to the self. In one study, subjects sat in front of a microcomputer and looked at forty trait words (for example, shy, friendly, ambitious). In some cases, they were told to judge whether the words were self-descriptive; in others,they judged the word’s length, sound, or meaning. When asked to list as many of the words as they could, subjects remembered more after thinking about the words in reference to themselves than for other purposes. Apparently, the self can be used as a memory aid: By viewing new information as relevant to ourselves, we consider that information more fully and organize it around common themes. The result is an improvement in recall. Hence, why I tell you guys to try and personalize this material as much as possible, even if it is just coming up with examples of when these things have happened to you…it increases your likelihood of remembering it for the exam.

Although the transfer of information to long-term memory often requires a great deal of thought and effort, certain types of information are encoded automatically and without conscious control. When you meet someone for the first time, you may have trouble remembering their name but you can easily recall their face. Similarly, people encode information about time, spatial locations, and event frequencies without conscious effort.

Long-term memory

Procedural (Implicit)
Memories of behaviors, skills, etc.
Demonstrated through behavior
Declarative (Explicit)
Memories of facts
Semantic – general knowledge
Episodic – personal experiences tied to places & time

It seems that we have more than one type of long-term memory. Researchers now commonly distinguish two types of memory. One is procedural memory, a ‘know how’ memory that consists of our stored knowledge of well-learned habits and skills – such as how to drive, swim, type, ride a bike, and the tie shoelaces.

The second type is declarative memory, which consists of both semantic memories for facts about the world – such as who Michael Jordan is, what a dollar is worth, what you need to access the World Wide Web, and what the word ‘gravity’ means – and episodic memories that we have about ourselves – such as who our parents are, where we went to school, and what our favorite movie is. The distinction is important because people with amnesia are often unable to recall declarative memories of facts and events, yet they still retain many of the skills they had learned and committed to procedural memory.

With all that’s stored in long-term memory – habits, skills, verbal information and knowledge of the words, names, dates, faces, pictures, personal experiences, and the like – it’s amazing that anything can ever be retrieved from this vast warehouse. Surely our knowledge must be organized in memory, perhaps the way books are filed in a library. One popular view is that memories are stored in a complex web of associations, or semantic networks. According to proponents of this view, items in memory are linked together by semantic relationships. When one item is brought to mind, the pathways leading to meaningfully related items are primed – thus increasing the likelihood that they too will be retrieved.

A good deal of research supports the notion that memories are stored in semantic networks. When subjects are given a list of sixty words that fall into four categories (animals, professions, names, and fruits) – even if the words are presented in a mixed order – subjects later tend to recall them in clusters. In other words, retreiving tiger is more likely to trigger one’s memory for baboon than for dentist, Jason, or banana.

Types of Long Term Memory

Semantic memory

Episodic memory

Procedural memory

Declarative memory

“I remember buying my first guitar.”

“I know what a guitar is.”

“I remember how to play a guitar.”

Semantic Networks

Red

Fire

Cherry

Roses

Fire Engine

Apples

House

Green

Flowers

Daisies

Yellow

Orange

Truck

Bus

Ambulance

Sunrise

Sunsets

Clouds

Levels of Processing: Retrieval

Retrieval
Process that controls flow of information from long-term to working memory
Explicit memory
The types of memory elicited through the conscious retrieval of recollections in response to direct questions
Implicit memory
A nonconscious recollection of a prior experience that is revealed indirectly, by its effects on performance

Once information is stored, how do you know it exists? Because people can openly report their recollections, this seems like a silly question. In fact, however, this is one of the thorniest questions confronting cognitive psychologists. Hermann Ebbinghaus was not only the first person to study memory systematically but also the first to realize that a memory may exist without awareness. In his words “These experiences remain concealed from consciousness and yet produce an effect which is significant and which authenticates their previous experience.”

Memory without awareness illustrates how human beings can be both competent and incompetent at the same time, and it poses a profound challenge to the researcher: If people have memories they cannot report, how can we ever know these memories exist? To his credit, Ebbinghaus devised a simple but clever technique. He tested memory by its effect on performance. Acting as his own subject, he would learn a set of nonsense syllables and then count the number of trials it later took him to relearn the same list. If it took fewer trials the second time around than the first, then he must have retained some of the material – even if he could not consciously recite it.

In recent years, other techniques have been devised. Basically, there are two types of tests, and each assesses a different type of memory; one explicit, the other implicit. Explicit memory is a term used to describe the recollections of facts and events that people try to retrieve in response to direct questions. In contrast, implicit memory is a term used to describe the retention of information without awareness, as measured by its indirect effects. Why is this distinction important? The reason, as we’ll see, is that people often exhibit dissociations between the two types of tasks. That is, people will consciously forget (have no explicit memory) of that experience. There are different ways to interpret this pattern. Some psychologists believe that explicit and implicit memory are separate systems that are controlled by different parts of the brain, whereas others believe that the dissociations merely indicate differences in the way information is encoded and retrieved. Either way, it’s useful to consider these two aspects of memory separately.

Retrieval – Explicit Memory

Free-recall test

Recognition task

Retrieval failure
Tip-of-the-tongue (Brown & McNeill)

Okay, can you all name all of Walt Disney’s Seven Dwarfs? Try it. When I was put to the test, I could only name about four…I always forget about Bashful, Sneezy, and Happy! This type of task, in which a person is asked to reproduce information without the benefit of external cues, is an example of a free-recall test of explicit memory. Other examples include taking an essay exam, describing a criminal’s face to the police, and struggling to recall a childhood experience. Now if I had given you a list of ten possible dwarf names and asked you to indicate which of them are accurate, that would have been a recognition task. This task requires you to select a remembered item from a list of alternatives. So are taking a multiple-choice exam and picking a criminal from a lineup, or identifying photographs from a family album.

Research shows that recall and recognition are both forms of explicit memory in that people are consciously trying to retrieve the information. There is, however, a key difference: People tend to perform better at recognition. The seven dwarfs task illustrates the point. When college students were asked to recall the characters on their own, they correctly produced an average of 69% of the names. Yet, when they made selections from a list, the accuracy rate increased to 86%.

The fact that recognition is easier than recall tells us that forgetting sometimes occurs not because memory has decayed or because we didn’t encode the information but because the information is difficult to reclaim from storage. Retrieval failure is a common experience. Have you ever felt as thought a word or name you were trying to recall was just out of reach – on the tip of your tongue? In a classic study of the tip-of-the-tongue phenomenon, Brown & McNeill prompted this experience by giving students definitions of uncommon words and asking them to produce the words themselves. For example, what is ‘the green-colored matter found in plants’? And what is ‘the art of speaking in such a way that the voice seems to come from another place’? Most often, subjects either knew the word right away or were certain that they did not know it. But at times, subjects knew they word but could not recall it – a frustrating state that they likened to being on the brink of a sneeze.

The experience is an interesting one. When a word is on the tip of the tongue, subjects often come up with other words that are similar in sound or meaning. Groping for chlorophyll, subjects might say chlorine or cholesterol. For ventroliquism, they produce words such as ventilate or vernacular. In fact, a surprising number of people will guess the correct first letter, last letter, and number of syllables contained in the missing word.

Recognition is often easier than recall because recognition tasks contain retrieval cues, or reminders. A retrieval cue is a stimulus that helps us to access information in long-term memory. Any stimulus that is encoded along with an experience can later trigger one’s memory of that experience. The retrieval cue may be a picture, a location, a word, a song, another person, or even a fragrance or the mood we’re in.

Retrieval – Explicit Memory

Context-Dependent Memory
We are more successful at retrieving memories if we are in the same environment in which we stored them

State-Dependent Memory
We are more successful at retrieving memories if we are in the same mood as when we stored them

This principle that any stimulus encoded along with an experience can later jog one’s memory of that experience led to an interesting notion that memory is ‘context dependent’ – that people find it easier to retrieve information from memory when they’re in the same situation in which the information was obtained in the first place. In an unusual initial test of this hypothesis, researchers presented scuba divers with a list of words in one of two settings: fifteen underwater or on the beach. Then they tested the divers in the same setting or in the other setting. Illustrating context-dependent memory, the divers recalled 40% more words when the material was learned and retrieved in the same context.

This type of research has uncovered several applicable findings for you all: because test-taking situations are typically quiet, you recall more information if you also study in a quiet setting.

There’s no doubt about it, we can often jog a memory by reinstating the initial context of an experience. This explains why, when you walk into a room to get something and then completely forget why you went into the room – you can often re-remember the object of your task by going back into the room where you first thought of what you wanted.

Internal cues that become associated with an event may also spark the retrieval of explicit memories. Illustrating the phenomenon of state-dependent memory, studies reveal that it is often easier to recall something when our state of mind is the same at testing as it was during encoding. If you have an experience when you are happy or sad, drunk or sober, calm or aroused, that experience – unless your emotional state is intensely distracting – is more likely to pop to mind or be free-recalled when your internal state later is the same than when it’s different. Researchers have found that the reason it helps to be memory-tested in the same place where you learned the material is that the environment is likely to transport you back to the same mood state – and it’s this mood state that serves as a retrieval cue.

When it comes to internal states and memory, there is a complicating factor: The mood we’re in often leads us to evoke memories that are congruent with that mood. When people are happy, the good times are easier to recall. But when people are sad, depressed, or anxious, their minds become flooded with negative events of the past. Currently depressed people thus report having more intrusive memories of death and other bad experiences compared to nondepressed controls. You can see how destructive this cycle can get.

Retrieval – Implicit Memory

Showing knowledge of something without recognizing that we know it

Research with amnesics

Psychologist Donald Thompson

Unintentional plagiarism

With implicit memory – we’re really examining the fact that we show knowledge of something without being able to ‘know’ and recognize that we know it. Early researchers believed that amnesics lacked the ability to encode or store information in long-term memory. They believed that they could still perform ‘skills’ – but could not keep new ‘information’ in memory.

Or could they?? Several case studies have shown that while amnesics may not be aware or conscious of the fact that they have learned a skill or set of information, they test higher than do people who have not been exposed to the stimulus. For example, one amnesic was asked to be interviewed in a room where they had taken part in a number of experiments. The amnesic agreed but stated that he would have to be shown where the room was…except that he had already turned in the right direction and walked right to it with no help.

This dissociation – the tendency for amnsesics to show signs of long-term retention of information without awareness – has now been amply observed in studies involving different types of amnesia and different implicit-memory tests. For example, researchers tried to classically condition to an anterograde amnesia patient by pairing a harmless tone with electric shock. Although the patient could not later recall these sessions, he reacted with greater arousal whenever the tone was presented.

You don’t have to suffer brain damage or drug-induced amnesia to exhibit a dissociation between memory and awareness. Have you ever had the eerie feeling that you’ve been in a situation before, even though you had not? Déjà vu is defined as the illusion that a new situation is familiar. In a way, déjà vu is the opposite of amnesia. Whereas amnesics have memories without awareness or familiarity, the person with déjà vu has a sense of familiarity but no real memory. Estimates vary, but between 30 and 96% of people report having had such an episode.

Déjà vu is not the only type of association that is commonly experienced. Retention without awareness occurs in all of us – sometimes with interesting consequences.

Retention without awareness can also have serious consequences. Several years ago, psychologist Donald Thompson was falsely accused of rape on the basis of the victim’s recollection. Luckily for Thompson, he was being interviewed lived on television as the rape occurred – an interview, ironically, on the subject of human memory. Apparently, the victim was watching Thompson’s show just before being attacked and then mistook him for the rapist. Was Thompson familiar to her? Yes, he was – but from the TV show, not from the crime scene. Thanks to his airtight alibi, Thompson was instantly vindicated. Perhaps others have not been so fortunate.

The problem illustrated by this story is that sometimes witnesses remember a face but forget the circumstances in which they saw it. In one study, subjects witnessed a staged crime and then looked through mug shots. A few days later, they were asked to view a lineup. The result was startling: Subjects were as likely to identify an innocent person whose photograph was in the mug shots as they were to pick the actual criminal. This familiarity effect gives rise to the phenomenon of eyewitness transference, whereby a person seen in one situation is later confused in memory, or ‘transferred’, to another situation – often with tragic consequences.

Unconscious transference occurs when we are aware that something is familiar but we cannot pinpoint the correct source of that familiarity. In other words, the experience has an impact on behavior, but without our conscious awareness. There is another possible repercussion of implicit memory: unintentional plagiarism. In 2002, two popular historians and authors, the late Stephen Ambrose and Doris Kearns Goodwin were accused of lifting passages without quotation from other sources. Most of the sources were credited in footnotes, and both authors said the omission of quotation marks around the borrowed material was inadvertent, the unconscious result of careless record-keeping.

Have you ever had an insight you thought was original, only later to realize or be told that it was ‘borrowed’ from another source? Are people who write, compose music, solve problems, tell jokes, or think up creative ideas vulnerable to unintentional plagiarism? Researchers had subjects in groups take turns generating items that fit a particular category (sports, four-legged animals, musical instruments, and clothing). After four rounds, they asked subjects individually to recall the items that they personally had generated and to come up with new ones from the same categories. As it turned out, 75% of the subjects took credit for at least one item of someone else’s, and 71% came up with a ‘new’ item that was given earlier. Some subjects inadvertently plagiarized their own ideas, but most often they ‘stole’ from others in the group.

Additional research has shown that people are vulnerable to unintentional plagiarism in some situations more than others. Predictably, the problem is more likely to occur when the ideas taken are highly memorable, when the person who gave the original ideas has status, when the original ideas were shared in anonymous group situations, when subjects were distracted or in a hurry or not overly concerned about the origin of their ideas, and after a long period of time has elapsed. These studies show that there is a bit of amnesia in all of us. Commenting on the amount of unconscious plagiarism exhibited by research participants in the lab, psychologists speculate that the problem is a lot more common than anybody would realize.

Forgetting and Why It Occurs

If we remembered everything, we should on most occasions be as ill off as if we remembered nothing.

William James

Decay theory

Unused memories fade gradually over time

Causes of forgetting
Memory traces fade over time
Interference with retrieval

Interference theory

Forgetting is a result of some memories interfering with others
Proactive interference
Old memories interfere with ability to remember new memories

By showing that memory loss may be caused by mental activity that takes place when we are awake, Jenkins & Dallenbach’s study suggested a third explanation of forgetting – that something learned may be forgotten due to interference from other information. There are two kinds of interference. In proactive interference, prior information inhibits our ability to recall something new. If you try to learn a set of names, formulas, phone numbers, or glossary terms, you will find it more difficult if you had earlier studied a similar set of items. Many years ago, researchers found that the more nonsense-syllable experiments subjects had taken part in, the more forgetting they exhibited in a brand-new study.

A related problem is retroactive interference, whereby new material disrupts memory for previously learned information. Thus, subjects in various experiments are at least temporarily less likely to recognize previously seen pictures of nature scenes, faces, and common objects if they are then exposed to similar photographs before being tested. One learning experience can displace – or at least inhibit – the retrieval of another. That is why, when people go back and review a subset of to-be-remembered information, their memory for nonreviewed material suffers.

Interference theory

Retroactive interference
New memories interfere with ability to remember old memories

Amnesia: Disorders of Memory

Retrograde amnesia

No memory of what happened immediately before an accident or highly stressful event

Little or no disruption in STM

New long-term memories can be formed

Usually memory loss does not last lifetime

Stress of event disrupts consolidation and retroactive interference blocks retrieval

Amnesia: Disorders of Memory

Anterograde amnesia

Inability to store and retrieve new information

Does not affect procedural memory abilities but disrupts episodic memory formation

Hippocampus involved in episodic memory

Damage prevents formation of new long-term declarative memories

Amnesia: Disorders of Memory

Korsakoff’s syndrome

Brain disorder from prolonged loss of vitamin thiamine as in diet of chronic alcoholics

Extreme degree of memory loss

Often engage in confabulation – cannot remember ending to a statement so make it up; or repeat the same story over and over.

Inaccurate Recall Due to Biased Questioning

Research on eyewitness information

Can be potent source of distortion

Interviewer questions can contain cues that influence retrieval

Reconstruction theory of forgetting – people remember something that did not occur because it seemed consistent with the event

Perceived expertise of interviewer may bias informational response

Stereotypes and Eyewitness Testimony

Allport: memories distorted by prejudices

Research in US – common African American names more stereotyped with criminality when memories fit personal schemas of prejudice

Inaccurate recall due to characteristics of the eyewitness

Being tired, upset, intoxicated may effect recall

Drunk eyewitness: visual recall may be accurate in some circumstances

Recall of Repressed Memories of Sexual and Physical Abuse

Most compelling testimony is from victims

Many cases of repressed memories when adult was abused as child now in media

Dilemma - hard to know what is accurate

Many traumatic childhood memories discovered in psychotherapy may be false memories

Hypnosis and Eyewitness Testimony

Hypnotizing witnesses to crimes is controversial

Hypnotic age regression: hypnotized person goes back in time to earlier age – relives event and recalls forgotten experiences

May be heightened imagination more than accurate relived memories

Hypnotized witnesses to recent crimes controversial

Improving the Accuracy of
Eyewitnesses’ Testimony

Thousands of experiments in research have raised concerns but little has been done

DNA saved innocent persons on death row convicted on eyewitness testimony

Improving Memory

Practice time
Distribute your studying over time
Depth of processing
Spend ‘quality’ time studying
Verbal mnemonics
Use rhyming or acronyms to reduce the amount of info to be stored

Over the years, psychologists have stumbled in a few rare individuals who seem equipped with extraordinary ‘hardware’ for memory. But often, the actors, waiters, and others who impress us with their extraordinary memories are ordinary people who use memory tricks called mnemonics. Can you too boost your recall capacity and improve your study skills by using mnemonics? Let’s consider the self-help implications of this chapter, many of which are described in paperbacks on how to improve your memory.

To learn names, dates, vocabulary words, or the contexts in a textbook, you’ll find that practice makes perfect. In general, the more time spent studying, the better. Skimming or speed-reading will not promote long-term retention. In fact, it pays to overlearn – that is, to review the material even after you think you have it mastered. It also helps to distribute your studying over time rather than cram all at once. You will retain more information from four two-hour sessions that from one eight-hour marathon.

The sheer amount of practice is important, but only if it’s ‘quality time’. Mindless drills may help maintain information in short-term memory, but long-term retention requires that you think actively and deeply about material – about what it means and how it is linked to what you already know.

Sometimes the easiest way to remember a list of items is to use verbal mnemonics, or ‘memory tricks’. Chances are you have already used popular methods such as rhymes (I before E, except after C) and acronyms that reduce the amount of information to be stored (ROY G BIV).

Improving Memory

Interference
Study right before sleeping & review all the material right before the exam
Allocate an uninterrupted chunk of time to one course
Context reinstatement
Try to study in the same environment & mood in which you will be taking the exam

Most books on improving memory recommend that verbal information be represented as visual images. One popular use of imagery is the method of loci, in which items to be recalled are mentally placed in familiar locations. It works like this: First you memorize a series of objects along a familiar route. For example, you might imagine your morning walk from the bedroom, to the bathroom, visualize the objects you pass: your bed, then the bathroom door, shower, stairs, and so on. These places become pigeonholes for items to be recalled. To memorize a shopping list, for example, you could picture a dozen eggs lined up on the bed, a bag of red apples handing on the bathroom door, and butter in the soap dish of the shower. When you take a mental stroll through the house, the items on the list should pop to mind. The trick is to link new items to others already in memory.

Because one learning experience can disrupt memory for another, you should guard against the effects of interference. This problem is common among students, as material learned in one course can make it harder to retain that learned in another. To minimize interference, follow two simple suggestions: First, study right before sleeping and review all the material right before the exam. Second, allocate an uninterrupted chunk of time to one course; then do the same for the others. If you study psychology, then move to biology, then go on to math and back to psychology, each course will disrupt your memory of the others – especially if the material is similar.

Context reinstatement: Information is easier to recall when people are in the physical setting in which it was acquired – and in the same frame of mind. The setting and the mood it evokes serve as cues that trigger the retrieval of to-be-remembered information. That’s why actors like to rehearse on the stage where they will later perform. So next time you have an important exam to take, try to study in the room where you’ll take the test.

The End