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The Three Different Levels of Processing Information with Respect to Memory
Greg Levin
Edith Cowan University
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Abstract
This paper looks at the levels of processing within memory according to the modal
model. This model proposes that memory has three distinct levels, sensory memory,
short-term memory and long-term memory. Each level has its own unique set of
attributes. Experiments conducted have managed to identify that differences do exist
and some of these will be more closely reviewed. There are also arguments against
the modal model being a true representation of memory and some of these opinions
will be expressed. Overall the model is good foundation upon which understanding
into memory can be built.
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The Three Different Levels of Processing Information with Respect to Memory
During our lives, humans are faced with the prospect of constantly having to
remember many different things. These range from names and important dates to such
things as shopping lists and telephone numbers. It is because of memory that we are
able to recall information. Memory is defined by Bernstein and Nash (2002) as “a
complex process of encoding, storing, and retrieving information” (p. 179). Encoding
is the process of changing the information into a form that can be understood and
accepted in order to be stored into memory (Bernstein & Nash; Wade & Tavris,
1998). The information is then stored in the memory and held there until further
required. The final step of retrieving the information occurs when the information is
recalled from storage and is used (Bernstein & Nash).
This paper will look at the levels of processing within memory. It has been
suggested that memory comprise of three different levels of processing (Craik &
Lockhart, 1972; Wade & Tavris, 1998). This three level system is known as the modal
model or the three box model (Craik & Lockhart). The levels that make up this model
are sensory memory, short-term memory (STM) and long-term memory (LTM).
All information initially enters our memory through our senses. If we do not
see something then there is no way that we will be able to know exactly what it looks
like. Therefore the first level at which information is processed is at a sensory level.
Information entering sensory memory does so automatically. There is no requirement
for a person to be paying attention to what is seen, felt, heard, or smelt yet all this
information will be processed regardless (Pashler and Carrier, 1996; Craik &
Lockhart, 1972). Consequently it is not possible to control what enters sensory
memory. The most common sensory registers used are the visual (iconic) and auditory
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(echoic) registers (Baddeley, 1990). Each sense is believed to have its on register,
which holds the information taken in for further processing.
The holding period is only of very short duration. Pashler and Carrier (1996)
suggest that iconic memory lasts only a several hundred milliseconds while the range
is increased for echoic memory. A period of one to two seconds has been proposed as
the maximum duration for auditory storage.
The second level of processing within the modal model is short-term memory.
STM differs from sensory memory in that all information that enters this stage does so
through active involvement and requires voluntary attention (Pashler and Carrier,
1996). STM is also known as ‘working memory’ because it used to hold all
information that is being used at a given point in time (Baddeley, 1992; Bernstein &
Nash, 2002). This would then mean that as well as sensory information being
processed to STM, information from LTM also moves into short-term store when it is
about to or is being used (Wade & Tavris, 1998).
Information at this level usually lasts between 18 and 30 seconds (Bernstein &
Nash; Craik & Lockhart, 1972). Information can be retained in STM for longer
periods using techniques such as rehearsal and repetition (Craik & Lockhart).
However if maintenance techniques are discontinued, and the information has not
been processed to LTM, the information will still be lost in the usual time frame
(Wade &Tavris, 1998).
STM has a relatively small capacity. It is believed that at any one time STM
can hold only between five and nine pieces of information (Baddeley, 1990). This
figure is based on controlled tests performed in laboratories and may therefore vary
once analysed outside laboratory settings. This does not necessarily mean that only
between five and nine numbers, letters or pictures can be in STM. STM works in such
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a way that it groups together pieces of information into ‘chunks’ (Bernstein & Nash,
2002). The limit set for STM applies then to these chunks so that if a series of 21
numbers is divided into seven chunks of three numbers each, this sequence could
easily fit into STM.
An experiment conducted by Conrad (1964) as cited in Bernstein and Nash
(2002) revealed that coding at a STM level takes place acoustically. This was disputed
by Shand (1982) also cited in Bernstein and Nash. Shand found that deaf people
encoded information visually rather than acoustically, as they had no knowledge of
the sounds. Thus it can be said that material in STM is coded in a way that is most
familiar to that person.
The third and final level of processing occurs in long-term memory. Often
when people refer to memory, they are actually referring to LTM. LTM is knowledge;
it is the basis of everything that one knows. The storage capacity for LTM is believed
to be unlimited (Bernstein & Nash, 2002; Wade & Tavris, 1998). Information that is
stored in LTM is permanent and is not easily forgotten although it can become
distorted (Bernstein & Nash, 2002). Distortion of information means that although a
thought may appear to be the original memory, it has changed in some shape or form.
Often when memory does become distorted the individual is unaware and does not
realise that the actual memory has altered in any way.
Information entering this level normally does so by way of added attention and
extra processing. Occasionally, information will enter LTM without any effort
(Bernstein & Nash, 2002). As opposed to STM information in LTM is coded
semantically (Wade & Tavris, 1998). According to Bernstein and Nash semantic
coding is the process whereby information is stored not as an exact replica but by its
general meaning. Evidence that suggest that information is semantically coded in
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LTM exists in the form of many studies. One such study performed by Sachs (1967 as
cited in Baddeley, 1990) indicates that when people are given information and then
distracted for a short period of time they are unable to recall the exact information but
have an understanding of what the information was about.
Empirical evidence has shown that there is definite separation between STM
and LTM. Firstly the Brown-Peterson procedure looked at the way that information
was forgotten. It determined that there were two distinct sources of memory STM, in
which information was lost through the process of trace decay, and LTM, in which
information was lost through the process of interference (Baddeley, 1990). The idea
that information was forgotten in different ways, at various stages of processing
justified belief in a dichotomous view of memory.
Another, and even more, convincing method of representing a division in postsensory memory can be viewed in people suffering from brain damage. People that
suffer brain damage may lose full function of either short-term or long-term memory.
Anterograde amnesia is a disease, which inhibits the formation of new LTM without
having a visible effect on STM (Neimark, 1995). Several studies (Baddeley, 1990;
Neimark; Pashler & Carrier, 1996) have demonstrated that sufferers of this disease are
able to engage in activities requiring the use of STM with no effects, yet a few
minutes later the same sufferers are unable to remember what they had just said or
done.
In a further study by Shallice and Warrington (1970 as cited in Baddeley,
1990) the opposite result was found. Their patient displayed signs of having a normal
LTM but a drastically reduced STM. This finding was very important because it
exemplifies further that there are two distinct levels of memory. It ruled out any bias
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in the testing regime and proved that information is processed on more than one level
and in more than one way.
There are however some drawbacks to the modal model. One of these is seen
in the way that information is processed. According to the modal model one of the
criterion used to differentiate different sensory, STM and LTM from each other is the
way in which they are processed. However there is research (Baddeley, 1990) that
explains the existence of sensory short-term and sensory long-term memory. Shulman
(1970 as cited in Craik & Lockhart, 1972) has also suggested that it is possible for
information in STM to be coded semantically.
Another argument against the box system is the concept of parallel processing.
If information has to pass through each level before entering the next (i.e. Sensory ->
STM -> LTM) then there arises a problem with those people who suffer anterograde
amnesia. The sufferers who have impaired STM should according to this system also
have difficulty in creating new long-term memories, because of the route that the
information takes. If the information can not be processed at STM then it should not
be able to move into LTM (Baddeley, 1992). Recall from LTM in such cases should
also be difficult because all information being used supposedly is held in working
memory (Baddeley, 1990).
In conclusion, there is enough evidence to suggest that the three way model of
memory does exist. Sensory, short-term and long-term memories have all been shown
to posses their own distinct qualities, which individualises them from each other.
Despite the problems associated with the model and the likelihood that it is not a
completely accurate representation of memory its use as a tool in the understanding of
how memory functions can not be doubted.
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References
Baddeley, A. (1990). Human memory: Theory and practice. Boston: Allyn and
Bacon.
Baddeley, A. (1992). Working memory. Science, 255, 556 – 559.
Bernstein, D.A., & Nash, P.W. (2002). Essentials of psychology (2nd ed.). USA:
Houghton Mifflin.
Craik, F.I.M., & Lockhart, R.S. (1972). Levels of processing: A framework for
memory. Journal of Verbal Learning and Verbal behaviour, 11, 671 – 684.
Neimark, J. (1995). It’s magical! It’s malleable! It’s … memory. Psychology Today,
44 – 49.
Pashler, H., & Carrier, M. (1996). Structures, processes, and the flow of information.
In E.L. Bjork & R.A. Bjork (Eds.), Memory (pp. 4-25). USA: Academic Press.
Wade, C., & Tavris, C. (1998). Psychology (5th ed.). USA: Longman