In the last section we began an examination of some
factors that influenced memory. In this section, we want to begin an
examination of some early theories of memory or what are called stage or
multiprocess theories. Of these stage or multiprocess theories the best of
these is described by Atkinson and Shiffrin. So let’s begin with a
discussion of some of these stage or multiprocess theories. This is shown in
slide two.
In slide two, there’s a schematic of the Atkinson and
Shiffrin model and we’re going to walk through this model. You will need to
keep coming back to this slide off and on, so you might print it off so you
have an idea about what it is. Let’s look at the first aspect of the sensory
system.
The first thing you need to note right off the bat is that
you have some kind of a sensation and the sensation can be anything. It can
be an auditory sensation, a tactile sensation, a visual sensation, etc., and
this sensation moves into what Atkinson and Shiffrin call sensory memory. In
sensory memory (as we see in slide three), sensory impressions are stored in
a form similar to the original sensation and there’s a wide variety of
different sub-groups. Let’s look at the first one of these which is called
Iconic memory.
Iconic memory is related to the visual system. Basically
these are visual images in the retina and the brain that last approximately
a quarter second. They can also last longer, but usually they’re gone within
a quarter second. One question (if you’re asking) is why does this image
stay within the visual system. That’s because your bipolar, ganglion,
amacrine, and horizontal cells in your retina and other cells within your
brain primarily in the superior colliculus and occipital lobe are working
and processing the different pieces of material.
Now you may ask, “Well what really is an iconic memory,
how do I know what it is?” So, what I’d like you to do is find something in
the room and start looking at it. The object can be anything. So find
something and look at it. Then I want you to close your eyes and note what
you immediately see right after you close your eyes.
What you will see is that object. It will last for a
little bit of time and then fade away. That is sensory iconic memory.
Now the next type of sensory memory relates to what is
called echoic memory. This is shown in slide five. Echoic memory is related
to your auditory system. Basically these sounds are in your cochlea and in
your temporal lobe. They last two seconds, or less, but sometimes an last
longer. Again the question is why. The reason is the sound waves you have in
the cochlea are occurring. You have fluid waves occurring there. As a
result, you continue to hear things. Now, this duration can last longer than
two seconds. A classic example would be if you go out and listen and
somebody shoots off a firecracker right behind you. How long does the sound
last. Well, the sound can last longer than two seconds. In fact, it can last
five to ten seconds. And if the sound is really loud, it can last twenty
seconds. So you have two memory systems that are related to what we call
sensory memory. There are also other types of sensory memory as well but
these two are the most important.
Well let’s go back now and look at slide two again. What
we have is information that’s going into our sensory memory. Once this
material is in sensory memory, two things can happen. Number one, is you can
pay attention to the particular item and if that’s the case, the information
moves into the next memory system that is called short term memory which
we’ll talk about in a minute. Number two, if you don’t pay attention to the
particular item, the particular item is forgotten.
So let’s say that you pay particular attention to some
kind of an iconic or echoic memory and it moves into short term memory.
Let’s talk about short term memory, what it is, and how it works. We begin
in slide six.
Basically short term memory consists of two things; first,
events that have just occurred that are still in your consciousness. So what
I just said a minute ago might still be in there. Second, different events
that are brought back by recall from long term memory. So, short-term memory
can consist of things that have just occurred, or information that you
brought back from long-term recall.
Now as we see in slide seven, information in short-term
memory can do one of three things. This is shown in slide two with a
graphic. Number one, it can be rehearsed and remain in short term memory.
Or, however, if it is not rehearsed, it is forgotten. So you just lose it.
Or, finally it can go enter the next stage of memory (long term memory). So
in each case, the memory that you have in short term memory is going to do
one of those three things. You can rehearse it and keep it in there, if you
don’t rehearse it, the memory goes away, or it can go into long term
storage.
Well we have this information within our short term
memory. The question became, “What’s the capacity of short term memory?”
This is shown in slide eight and relates to seven plus or minus two. The
capacity of STM was shown by Miller at Bell Labs. What Miller found is that
you recall seven plus or minus two chunks or items that you can retain in
short term memory. However, it lasts a very brief/short period of time (ten
to twenty seconds). That is one reason (Miller worked for Bell Labs, ala
Bell Telephone), why your telephone number is seven items. Or if it’s seven
chunks of items, you basically have a one and international code, an area
code and then your local prefix and finally your number. So, you can recall
your phone number (with a maximum of about twenty to thirty digits of
information) because you chunk it out.
The same is true with your social security number and
other types of things. So, seven plus or minus two chunks of information is
important. Now this seven plus or minus two has extreme implications for
test taking. We demonstrate this in slide nine. Let’s say that you’re going
to cram for an exam that you need to take in an hour. You’ve been studying
all this stuff and you’ve been cramming to get the final pieces of
information in there. Then you walk into the room and you get your test.
What do you do? Well if you normally do things, you start with question one
and answer it. Then you answer question two. By the time you get to question
three, (which was the information that you were cramming for), lo and
behold, the information is gone. Poof. So, what’s the solution to help
yourself? Well, as soon as you get the exam, write the material down that
you’re trying to remember as soon as you get it.
Here’s one example of the way people write things down.
They take the first item and they write it down, they take the second item
and write it down, then take the third item and write it down. Twenty
seconds has now elapsed. So, when they get to the fourth item, what happens?
Poof, it’s gone. So what’s the best way to record things? Well, write down
the first item, then rehearse the list. That keeps the information in short
term memory. Then you write down the second item and rehearse the list. And
on and on until you have all the material that you’re tried to memorize.
Then you can then use other techniques to answer the remaining questions.
So again, short term memory has a limited amount of
material that you can store. It also has a limited duration of time which
the information remains. So you have to be very careful with how you are
working if you’re trying to retain stuff within a short term memory system.
Now, we have this information within short term memory and
we’re trying to remember it. What happens to that information? Well
ultimately it moves into the next stage as we saw in figure two, and that is
called long term memory. Long term memory, as we see in slide 10, is where
the information in essence goes and is retained.
Well, what’s the duration of long term memory? Well, it’s
basically forever. The classic studies that really show memory duration was
done by Walter Penfield the great Canadian neurosurgeon. What he did
occurred while he was performing brain surgery on folks. During the
procedure, he would use a small micro-electrode to stimulate parts of the
brain while the patient was conscious. And this is a common technique that’s
used in neurosurgery to identify structures and things that you do not want
to destroy if at all possible. While the person is under surgery, Penfield
would touch certain areas of the brain and memories would come back;
memories that the person had not thought of for 10, 20, 30 or 40 years. For
example, people in their 50s had childhood memories they had totally
forgotten or repressed. So, it appears once we have the information in
there, says Penfield and others, it seems to be retained forever.
So the question then becomes, “Hw do we get the
information into long term memory?” We show this in slide 11. How we do
this, says Atkinson and Shiffrin, is through rehearsal. We use information,
rehearse the information in short term memory long enough for transfer to
take place. So what’s this rehearsal thing called that you do? Atkinson and
Shiffrin called it elaborative rehearsal. Basically (as we see in slide 12),
what we do is relate information to information already stored in our long
term memory. So we think of things, what they mean, and how they relate.
Thus the better you organize the information, the easier it is to relate and
store the information. So again, those storage factors and those
organizational factors that we have discussed are very, very important to
keeping and putting information into our long term memory system.
So now we’ve taken material in. We have got it into the system, we’ve got it
through short term memory, and it’s now stuck in long term memory. The next
question is, “How do you get it out?” This is shown in slide 13. There are a
lot of different theories about how we get the information out, but two are
the standards. The first one relates to retrieval cues and the second one
relates to memory searches.
So let’s look at retrieval cues first on slide 14.
Retrieval cues are basically stimuli that open pathways to the memory, and
there are lots of different types of stimuli that you can use. For example,
words, pictures, odors, sensations, etc. So cues, in essence, open some
pathway and you then recall that information.
A related concept relates to what is called Encoding
Specificity. In encoding specificity as we see in slide 15, the more
specific the context where the item is learned to where the item is
recalled, the higher the probability of the recall. That is, the more
similar the context of the learning and recall conditions, the better the
learning. So, it’s very similar to state dependent learning. So, finding the
context (the item you are trying to recall) and how it is related to other
items, the better the recall that you will have.
Now the next theory of how you get the information out
relates to what we call memory searches. This is shown in slide 16. In
general, what this theory contends is that people engage in memory searches
for material; and we use one of two types. The first type is called a serial
memory search. The second is a parallel memory search. So, let’s look at
these in a little bit more detail.
Let’s look at a serial memory search first. A serial
memory search is like a serial task. So, the first thing is look at the item
and you ask, “Is it here?” If you say “No,” you then continue on. If it says
yes, then you do something. So let’s say that you ask, “Is the item here?”
If “Yes,” then you do something. If the system says, “No,” then the search
looks in a different place and asks, “Is it here?” and if it says “Yes,”
then you do something. If you say “No,” then you go on and you continue this
type of searching pattern until ultimately you find the particular item. So
in a serial memory search, what we have is a system where you go from one
item or place to the next and then the next.
There is also a second type of memory search pattern and that is called a
parallel search pattern. Again we discuss this on slide 16. In a parallel
search, what you do is look for and find many items at once. So you have
many searches going on inside the system. It is similar to how Microsoft
Windows operates today (which is a much more powerful methodology than what
we had several years ago). It is also much more powerful (and faster) than
using a serial memory search.
So now we’ve talked about a variety of different things
related to how we get information out. Well what kind of long term memories
do we have? We begin on slide 18. There are a variety of different types of
long term memory. These different types of memories are listed on slide 19.
As we can see here, we start with sensory memory. We then
move the material into short term memory and then in the long term memory.
Within long term memory we have a couple of different types, we have
procedural memories and we have declarative memories which consist of
systematic and episodic memories and so let’s talk about each of these.
Let’s talk about episodic memories first on slide 20.
Basically an episodic memory is a memory for a very specific event. That is,
what happened or where did it happen, etc. The classic example might be
where you have your first kiss or where somebody asks you to marry them, or
your first child, or whatever it may be. All of these things are very
specific episodic memories.
The second type of long term memory system relates to what
is called declarative memory and we see this on slide 21. These are memories
for particular items of knowledge and they’re independent of the particular
occasion in which they’re acquired. In essence, declarative memories are the
sums of acquired knowledge that you have. All the works, all the symbols,
all the facts of words, all the appearance of objects and on and on that we
have within our memory system. This is the thing that makes you different
from many other organisms that are out there. Not only do you remember these
materials, you have been able and blessed with the capacity to pass on this
material to your offspring, and offspring in generations far beyond your
lifetime. So, the works that we have from Confucius and Buddha, and many
other things, 4,000, 5,000 years BC, is very, very, important and can still
be used and read today. So declarative memory is extremely important.
Now within declarative memories there are a couple of
different types. The first of these, as we see in slide 22, is semantic
memory. Semantic memory is basically the memory for words, the meanings of
words and concepts. There are also lots of strategies we use for semantic
memories. We use parallel searches, we use network models which like
exploring things where we got go from one item to another to another to
another.
The next method of memory is what we call visual memory
and this is what we call eidetic imagery, or what most of you call
photographic memory. Basically these are individuals who can recall detailed
images of visual scenes for long periods of time. It’s extremely rare. Less
than 5% of all kids are born with eidetic imagery, and less of that for
adults. The reason for fewer adults is that it decreases as we get older and
older. Also, kids rely on imagery more than adults.
The final memory that we talk about in long term memory
are what are called procedural memories. These are memories for physical
things like riding a bike, throwing a baseball, or whatever it may be.
So, in general, we have a variety of different memory
systems which ultimately allows us to recall things for long periods of
time.
In the next section we’re going to begin to discuss and
examine some brain structures that are involved with memory.
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