Memory is a fascinating process that has intrigued psychologists for decades. Over the past century, psychologists have realized that memory is an extremely complex process, which sometime acts in mysterious ways. For example, we all remember the

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Memory is a fascinating process that has
intrigued psychologists for decades. Over the
past century, psychologists have realized that
memory is an extremely complex process, which
sometime acts in mysterious ways. For example, we
all remember the location, time, age, and partner
with whom we shared our first kiss.
But what about more frequent memories, such as
identifying a U.S. penny? We all have handled
1000s of pennies, yet most people cannot identify
the correct one. To understand this strange
case and others, we have to understand the three
basic processes of memory.
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Three enduring questions that psychologists ask
of memory, correspond to these three key
processes. These processes and memory itself are
often viewed as analogous to a modern day
computer. The first question is, how does
information get into memory? Like a scanner or
copier, we have to encode stimuli into a language
our brain understands. The second question is,
how is that information stored or maintained into
memory? Like hard drives in computers,
information is organized and stored for later
use. The third question is, how is the stored
information retrieved or pulled back out of
memory? Like a computer monitor retrieving
information to display, we too call up
information and display it in various forms
(e.g., talking, thinking, moving). Although
technology serves as a nice analogy, the inner
workings of our memory are far more complex.
We will begin with encoding, which involves
forming a memory code from some stimulus. There
are multiple levels of processing, which we will
get to soon, but we first have to address a
vital aspect of memory attention, which involves
focusing awareness on a narrowed range of
stimuli. Its probably not a shock to you that
attention is crucial to memory. For example, no
matter how many hours you listened to me talk
about memory, if youre not paying attention, you
will forget most of it. Memory is negatively
affected by inattention, especially when we try
to multi-task, as in driving while talking on a
cell-phone. One study investigated this and found
that talking on a cell phone seriously impaired
their braking skills. Those talking on the cell
phone ran more red lights and took longer to
brake.
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While attention is necessary, there are
qualitative differences in how you attend to
something. If youre talking on a cell phone in
a car with the music in the background, youre
likely attending to the conversation more than
the music, the music more than your foot on the
gas pedal, etc These differences in attending
affect how well we remember things and form the
levels-of-processing theory. In this theory, the
most basic type is structural encoding.
Structural encoding is shallow processing that
emphasizes the physical structure of the
stimulus, as in encoding the shapes that form
letters in the alphabet. The next level of
encoding is phonemic, which emphasizes what a
word sounds like, as in reading aloud or to
oneself. The last and deepest level of encoding
is semantic, which emphasizes the meaning of
verbal input. This level of encoding requires
thinking about the content and actions the words
represent, as in understanding the meaning of an
argument in an article.
Elaboration is a process by which a stimulus is
linked to other information at the time of
encoding. For example, you are studying phobias
for your psychology test, and you apply this
information to your own fear of spiders.
Elaboration often consists of thinking of
examples, and self-generated examples seem to
work best. Visual imagery involves the creation
of visual images to represent the words to be
remembered, and concrete words are much easier to
create images of (for example, juggler is easier
to visualize than truth). Dual-coding theory
holds that memory is enhanced by forming semantic
or visual codes, since either can lead to
recall. Self-referent encoding involves deciding
how or whether information is personally
relevant, that is, information that is personally
meaningful is more memorable.
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Now that we understand more about the process of
encoding and its importance, we turn now to the
next step in memory what is done with all the
information, which thanks to encoding, is now in
a language our brain can understand. How do we
organize and store information over time? This
and related questions were addressed by two
researchers Atkinson and Shiffrin. They proposed
that memory is made up of three memory storages
sensory memory, short-term memory, and long-term
memory. It is important to realize that, like the
computer example of memory, information
processing is a metaphor the three storages do
not refer to tiny lockers in the brain where
information actually sits.
Sensory memory is one of two temporary storage
buffers that information must pass through before
reaching long-term storage. As the name implies,
sensory memory preserves information through the
senses, in its original form (e.g., if you see
something, the sensory memory is vision, not any
other sense). Whats great about sensory memory
is that it allows us to experience a visual
pattern, sound, or touch even after the event has
come and gone. In doing this, sensory memory
gives us additional time to recognize things and
memorize them. But the extra time isnt much
for vision and audition, sensory memories only
last about .25 seconds. You can see this
characteristic of sensory memory, called an
afterimage, when a flashlight or sparkler is
moved about quickly, creating what appears to be
a continuous figure.
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After its brief stay in sensory memory,
information moves to what Atkinson and Shiffrin
called short-term memory. Short-term memory is
the second buffer, after sensory memory, before
information is stored long-term. Short-term
memory gets its name because it has a limited
storage capacity that can only maintain
information for 20 seconds. Several studies have
shown that when asked to recall basic
information, such as consonants, participants
perform poorly. Researchers attribute this poor
performance to time-related decay of memory, but
also to interference, as when other information
gets in the way of whats being stored. To
counteract time effects, many people use
rehearsal, the process of repetitively
verbalizing or thinking about information. In
doing this, they recycle the information back
into short-term memory. We all do this when we
have to remember bits of information we repeat
telephone numbers, e-mails, web addresses, etc.
In addition to time decay and interference,
short-term memory, like an iPod or hard drive,
has a limited capacity it can only store but so
much information. This was first discovered by
George Miller in the 50s, when he found that most
participants could only remember 7 plus or minus
2 digits. When we need to memorize more than
these amounts, the information already stored in
our short-term memory is displaced. But alas, we
have ways of overcoming the 7 plus or minus 2
rule. Rather than viewing information broken
into bits, we can store multiple bits as chunks,
a processing known as chunking. For example, take
the letters FBINBCCIAIBM. Few could recall
these from short-term memory, but by using
chunking, we can put these letters into
meaningful, easy-to-memorize units, such as
FBI-CIA-NBC-IBM. In this demonstration, we went
from working with 12 down to 4 pieces to
remember.
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Decades after Miller discovered the magic number
7 rule, Alan Baddeley proposed a more complex
model of short-term memory he called working
memory. His working memory theory divided
short-term memory into four components. The
first component is the phonological loop click
to enlarge. This component is nothing new it is
present in earlier models of short-term memory.
This component is at work when we recite or think
of information to keep it in our memory. The
second component is the visuospatial sketchpad
click to enlarge. This allows people to
temporarily hold and manipulate visual images.
For example, if you needed to rearrange the
clothes, shoes, and other junk in your closet,
the visuospatial sketchpad would be at work.
The third component is the central executive
system click to enlarge. This system is in
charge of directing and dividing focus and
attention. If youre listening to the TV, talking
on the phone, and trying to read for this class,
your central executive system is trying to manage
and divide your attention to these tasks. The
final component is called the episodic buffer
click to enlarge. In the episodic buffer, all
the information in short-term memory comes
together to be integrated in ways that allow it
to be passed on to long-term memory more easily.
The final stop for memory storage is in our
long-term memory. Long-term memory is an
unlimited capacity storage that can hold
information over long periods of time. One
question about the nature of long-term memory is,
after its passed on from short-term memory, can
the memories stay forever or do they fade out
with time? Think of long-term storage as a
barrel infinite in size, full of memories
represented by marbles. When we forget things, is
it because we cant find the right marble, or
is there a hole somewhere in our barrel where
memories can disappear?
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Some claim that flashbulb memories, which are
unusually vivid and detailed recollections of
momentous events, provide evidence that what gets
to long-term memory, stays there. Researchers
have found, however, that although some memories
stick around forever, they are often inaccurate
and people feel overly confident in their reports
of them. This information is extremely
relevant when considering eyewitness testimony.
The general consensus among psychologists is that
memories are formed in various ways depending on
many factors, such as the type of information
(e.g., fact vs. event). One way in which we
organize information is through our schemas.
Schemas are organized clusters of knowledge
about an object or event abstracted from previous
experience. For example, a schema of a classroom
might include desks, students, chalkboards,
teacher, etc. When confronted with a novel
classroom, we will more likely remember things
that are consistent with our schemas. However, we
also may remember things that violate our schema
expectations. So if you walk into a classroom,
and see an animal, youll likely remember that,
since most classroom schemas do not contain
animals. Another way we organize information is
through semantic networks. Semantic networks
consist of nodes representing concepts, joined
together by pathways that link related concepts.
For example, the phrase fire truck may be
organized in a network of similarly related
words, such as truck, fire, and red. In this
network, words closer to one another are more
strongly related. A final, much more complex
explanation of how we store knowledge is found in
parallel distributed processing, in which
cognitive processes depend on patterns of
activation in highly interconnected networks.
This more recent theory is being integrated with
what we are learning about neural networks in the
brain.
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This video shows how psychologists use high-tech
brain imaging procedures and computer simulations
to better understand learning and memory.
The journey into long-term memory is complex and
takes considerable effort, but reaching long-term
memory is only beneficial if youre able to
retrieve that information later. When you are
not be able to retrieve information that feels as
if its just out of your reach, you are
experiencing the tip-of-the-tongue phenomenon.
Though this shows a failure in retrieval,
researchers have shown that retrieval can occur
more frequently when retrieval cues are present.
Retrieval cues are stimuli that help gain
access to memories. Other cues, called context
cues can aid our retrieval of memories. Working
with context cues involves putting yourself in
the context in which a memory occurred. For
example, you may forget what you were looking for
when going from your bedroom to the kitchen, but
once you return to the bedroom you might remember
Oh yeah, I wanted a glass of water. This is
because the context clues in your bedroom help
you retrieve the memory.
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When we retrieve information, its never an exact
replay of the past. Instead, we pull up
reconstructions of the past that can be distorted
and include inaccurate information. Our poor
abilities to retrieve information accurately has
been extensively studied and is now known as the
misinformation effect, which occurs when
individuals recall of an event is altered by
misleading post-event information. A great
example was shown by Loftus and Palmer, in this
video click to play. Other research has
consistently found that people introduce
inaccuracies in the simple story-telling we do
every day. These findings have helped
psychologist understand that memory is not a
perfect process and that its more malleable than
once thought.
Another explanation for why we sometimes fail to
retrieve memories accurately is due to source
monitoring. Source monitoring is the process of
making inferences about the origins of memories.
Johnson and colleagues argue that when we store
memories, we dont label where/who we got them
from. They believe this process occurs when we
retrieve the memories. For example, you may
hear a blurb on CNN but may say your friend told
you about it earlier. This is an example of a
source monitoring error in which a memory derived
from one source is misattributed to another
source. Source monitoring can help us understand
why some people recall something that was only
verbally suggested to them or confuse their
sources of information.
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Although we normally think of forgetting as a
bad thing, its actually quite adaptive. Just
imagine the clutter we would have if we
remembered everything. But even with its adaptive
function, forgetting can be problematic, like
when we forget a definition of a term for a test,
or where our keys are, or worse. Psychologists
are interested in how and why we forget. One of
the first to research forgetting was Hermann
Ebbinghaus. Ebbinghaus used nonsense syllables
(random strings of vowels and consonants) as a
means of investigating memory. Interestingly,
he himself was the subject of his experiments,
and laboriously memorized nonsense syllables to
test his recall after various amounts of time had
passed he plotted these experiments to show a
forgetting curve. In doing this, he noticed that
he forgot a lot of the syllables shortly after
memorizing them. Though we now know that
memorizing things with meaning are less
forgettable than Ebbinhaus experiments, his
research spurred psychologists to consider how we
measure forgetting.
There are three general ways of measuring
forgetting, but psychologists prefer to use the
term retention, focusing on the proportion of
what is remembered, rather than what is
forgotten. First is a recall measure, which
requires a person to reproduce information on
their own without any cues. If asked to memorize
10 words then say them out loud, this would be a
recall test. Second is a recognition measure,
which requires a person to select previously
learned information from an array of options. All
students take part in this process when
completing multiple-choice or true-false
questions on exams. Third is a relearning
measure, which requires a person to memorize
information a second time to determine how much
time or effort is saved since learning it before.
For example, if it took you 5 minutes to memorize
a list of words and then only 2 minutes the
second time, your relearning measure would be 3
minutes. In other words, you remembered 60 of
what you memorized to begin with.
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The difficulty of a recognition test can vary
greatly, depending on the number, similarity, and
plausibility of the options provided as possible
answers. Many students find the question shown
to be difficult. What if the answer choices
were Jimmy Carter, John F. Kennedy, Harry Truman,
and James Madison? Click to continue Three
of these choices are readily dismissed, rendering
the question easier to answer.
Measuring forgetting is only half the battle. To
truly understand whats going on we have to
explore the possible causes for why we forget
factors that affect encoding, storage, and
retrieval. One explanation may be that we think
we are forgetting something, but in fact we never
learned it to begin with. The penny example
from earlier demonstrated this type of
pseudoforgetting. The problem at work here is
actually ineffective encoding due to lack of
attention, rather than any storage or retrieval
errors. Another explanation is that over time
memory traces fade away, known as the decay
theory. While this explanation has some merit,
much of our forgetting is actually better
understood through interference theory.
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Interference theory, which proposes that people
forget information because of competition from
other material, is a well-documented process and
can account at least for some of our forgetting.
One study by McGeoch and McDonald found that
the amount of interference depended on the
similarity between material. Click to continue
For example, when introducing an interference
task of synonyms, high interference occurred, but
with numbers that were not associated with the
test material, little interference occurred. This
type of interference in which new information
impairs previously learned information is called
retrograde interference. Proactive interference
is just the opposite, when old information
interferes with new information, as when your old
phone number interferes with your recalling the
new number.
Forgetting can also be because of failures in
information retrieval. For example, why is it
that we can remember a piece of information in
one setting but not in another? One explanation
has to do with the similarity between the
environment or way that we learned something and
the setting in which we try to retrieve it.
Lets pretend we learned a definition of
psychology in Spanish while in Mexico. We would
probably be more likely to recall that definition
in Mexico or maybe Spanish class, where retrieval
cues are more similar to the context in which it
was learned. This example highlights the
encoding specificity principle, which says that
the value of a retrieval cue depends on how well
it corresponds to the memory code. This
explanation of forgetting as well as the others
that have been mentioned seem as if they occur
automatically without our control, but there is
another theory of why we forget, one in which we
are motivated to do.
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Over a century ago, Freud offered a new
explanation for retrieval failures that we keep
distressing thoughts and feelings buried in the
unconscious. We repress memories or we are
motivated to forget. This theory or forgetting is
a hot and controversial topic in present-day
psychology, primarily due to a recent surge in
lawsuits in which a potential victim claims that
he/she was sexually abused, but just recently
recalled the repressed memory. Many psychologists
and psychiatrists believe that repressed memories
exist, as seen in many of their patients,
especially in abuse and other traumatic
experiences, but still others deny their
accuracy.
Many psychologists, especially memory
researchers, are skeptical of recovered memories
of abuse however, they do not imply that people
reporting these memories are lying or have bad
intentions. Instead, they point to findings on
the misinformation effect, source monitoring,
suggestibility, and leading questions as
contributors to the uncovering or repressed
memories. Skeptics also highlight cases in which
the truth about abuse has been found and the
memories proven false. Of course, rebuttals
from therapists are made on the account that
repression is a natural response to trauma and
dismiss much of the laboratory work on implanting
false memories. To say that all recovered
memories are false would certainly be incorrect,
but great caution must be taken in interpreting
these claims. Regardless of ones standpoint on
this issue, recovered memories have generated
large amounts of research and will continue to be
a focus for memory researchers.
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For decades, researchers have tried to trace the
physiological processes of memories and even to
pinpoint specific memories. As unfortunate as
serious head injuries are, they are a rich source
of information regarding the anatomy of memory.
After serious trauma, some individuals develop
amnesia, or extensive memory loss. Similar to how
interference is categorized, amnesia can be
either retrograde or anterograde. Retrograde
amnesia results in loss of memories for events
that occurred prior to the injury whereas
anterograde amnesia results in loss of memories
for events that occur after the injury. By
examining the brain structure and functioning of
individuals with serious brain injury, scientists
have identified some areas that may be important
in the consolidation of memories.
Consolidation refers to a hypothetical process
involving gradual conversion of information into
durable memory codes for storage in long-term
memory. These areas are those around the
hippocampus, which comprise the medial temporal
lobe. Other areas, such as the cortex, are
involved in memory, but the search for the
anatomy of memory is in its infancy.
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More detailed accounts of memory processes at the
cellular level over the past 20 years have led to
some intriguing theories about how we encode,
store, and retrieve memories. One theory,
developed by Thompson, suggests that memories
depend on localized neural circuits. That is,
memories may create unique, reusable pathways on
which signals flow. Future research in this area
may some day allow us to trace pathways of
specific memories. Another line of research
suggests that memories form because of
alterations in synaptic activity at specific
sites in the brain. Memories may also depend on
a process called long-term potentiation, which is
a long-lasting increase in neural excitability at
synapses along a specific neural pathway. A
final process called neurogenesis, or the
formation of new neurons, may also contribute to
the shaping of neural circuits that may underlie
memories. Newly formed neurons appear to be more
excitable than older ones, and this may mean they
can more quickly be used to form new memories.
Some memory theorists propose different systems
of memory. The most basic distinction is made
between declarative and nondeclarative memory.
Declarative memory handles factual information,
whereas nondeclarative memory houses memory for
actions, skills, conditioned responses, and
emotional memories. If you know that a bike has
two wheels, pedals, handlebars, etc., you are
using declarative memory. However, if you know
how to ride a bike, this is nondeclarative
memory. These two memory systems differ in
interesting ways. For example, writing out the
notes to a song (declarative) is effortful and
can be easily forgotten, but the process of
playing that song (nondeclarative) probably
involves less cognitive effort and is less
likely to be forgotten.
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If the medial temporal area of the brain is
destroyed, due to injury or disease, people often
develop amnesia. Learn how habit memory, a
second robust, but unconscious memory system,
plays a role in helping people with amnesia to
learn a declarative task.
Endel Tulving has further divided declarative
memory into two separate systems episodic and
semantic. Episodic memory is made up of
chronological, or temporally dated, recollections
of personal experiences. Episodic memory includes
all memories in which a time stamp is made.
That is, you remember an event associated with
some information. Semantic memory contains
general knowledge that is not tied to the time
when it was learned. For example, that January
1st marks the new year, dogs have four legs, etc.
are examples of information related to semantic
memory. An appropriate analogy is to think of
both as books. Episodic memory is an
autobiography whereas semantic memory is an
encyclopedia.
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Researchers have broken down memories not only
into systems, but also into two specific types
prospective and retrospective. Prospective
memory involves remembering to perform actions in
the future. For example, remembering to walk the
dog or take out the trash involve prospective
memory. Retrospective memories involve
remembering events from the past or previously
learned information. For example, in
retrospective memory you may try to remember who
won the Super Bowl last year or what last weeks
lecture covered. Research is under way to
determine whether these proposed systems
correlate with actual neural processes.
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