# Cognitive Psychology and Cognitive Neuroscience/Memory


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# Introduction

Imagine our friend Knut, who we have already introduced in earlier
chapters of this book, hastily walking through his apartment looking
everywhere for a gold medal that he has won many years ago at a swimming
contest. The medal is very important to him, since it was his recently
deceased mother who had insisted on him participating. The medal reminds
him of the happy times in his life. But now he does not know where it
is. He is sure that he had last seen it two days ago but, searching
through his recent experiences, he is not able to recall where he has
put it.\
So what exactly enables Knut to remember the swimming contest and why
does the medal trigger the remembrance of the happy times in his life?
Also, why is he not able to recall where he has put the medal, even
though he is capable of scanning through most of his experiences of the
last 48 hours?\
Memory, with all of its different forms and features, is the key to
answering these questions. When people talk about memories, they are
subconsciously talking about \"the capacity of the nervous system to
acquire and retain usable skills and knowledge, which allows living
organisms to benefit from experience\".[^1] Yet, how does this so-called
memory function? In the process of answering this question, many
different models of memory have evolved. Distinctions are drawn between
Sensory Memory, Short Term Memory, and Long Term Memory based on the
period of time information is accessible after it is first encountered.
**Sensory Memory**, which can further be divided into **Echoic** and
**Iconic Memory**, has the smallest time span for accessibility of
information. With **Short Term** and **Working Memory**, information is
accessible seconds to minutes after it is first encountered. While
**Long Term Memory**, has an accessibility period from minutes to years
to decades. This chapter discusses these different types of memory and
further gives an insight into memory phenomena like **False Memory** and
**Forgetting**. Finally, we will consider **biological foundations**
that concern memory in human beings and the biological changes that
occur when learning takes place and information is stored.

# Types of Memory

In the following section, we will discuss the three different types of
memory and their respective characteristics: **Sensory Memory**, **Short
Term (STM)** or **Working Memory (WM)** and **Long Term Memory (LTM)**.

## Sensory Memory

This type of memory has the shortest retention time, only milliseconds
to five seconds. Roughly, Sensory Memory can be subdivided into two main
kinds: framed\|Sensory Memory

-   **Iconic Memory** (visual input)
-   **Echoic Memory** (auditory input)

While Iconic and Echoic Memory have been well researched, there are
other types of Sensory Memory, like **haptic**, **olfactory**, etc., for
which no sophisticated theories exist so far.\
It should be noted, though, that according to the Atkinson and Shiffrin
(1968)`<ref>`{=html}Atkinson, R. C. & Shiffrin, R. M. (1968). Human
memory: A proposed system and its control processes.

:   In K. Spence & J. Spence (Eds.), *The psychology of learning and
    motivation (Volume 2)*. New York: Academic Press.
    ```{=html}
    </ref>
    ```
    Sensory Memory was considered to be the same thing as Iconic Memory.
    Echoic Memory was added to the concept of Sensory Memory due to
    research done by Darwin and others (1972).`<ref>`{=html}Darwin, C.
    J., Turvey, M. T., & Crowder, R. G. (1972). An auditory analogue of
    the Sperling partial report procedure:
:   Evidence for brief auditory storage. *Cognitive Psychology, 3*,
    255-267.
    ```{=html}
    </ref>
    ```
    Let us consider the following intuitive example for Iconic Memory:

Probably we all know the phenomenon that it seems possible to draw
lines, figures or names with lighted sparklers by moving the sparkler
fast enough in a dark environment. Physically, however, there are no
such things as lines of light. So why can we nevertheless see such
figures? This is due to Iconic Memory. Roughly speaking, we can think of
this subtype of memory as a kind of photographic memory, but one which
only lasts for a very short time (milliseconds, up to a second). The
image of the light of a sparkler remains in our memory (persistence of
vision) and thus makes it seem to us like the light leaves lines in the
dark. The term \"Echoic Memory\", as the name already suggests, refers
to auditory input. Here the persistence time is a little longer than
with Iconic Memory (up to five seconds).\
At the level of Sensory Memory no manipulation of the incoming
information occurs, it is transferred to the **Working Memory**. By
'transfer' it is meant that the amount of information is reduced because
the capacity of the working memory is not large enough to cope with all
the input coming from our sense organs. The next paragraph will deal
with the different theories of selection when transferring information
from Sensory Memory to Working Memory.\
One of the first experiments researching the phenomenon of **Attention**
was the **Shadowing Task** (Cherry et al., 1953).`<ref>`{=html}Cherry,
E. C. (1953). Some experiments on the recognition of speech with one and
with two ears.

:   *Journal of Accoustical Society of America, 25*, 975-979.
    ```{=html}
    </ref>
    ```
    This experiment deals with the filtering of auditory information.
    The subject is wearing earphones, getting presented a different
    story on each ear. He or she has to listen to and repeat out loud
    the message on one ear (shadowing). When asked for the content of
    the stories of both ears only the story of the shadowed side can be
    repeated; participants do not know about the content of the other
    ear's story. From these results Broadbent concluded the **Filter
    Theory** (1958).[^2] This theory proposes that the filtering of
    information is based on specific physical properties of stimuli. For
    every frequency there exists a distinct nerve pathway. The attention
    control selects which pathway is active and can thereby control
    which information is passed to the Working Memory. This way it is
    possible to follow the utterance of one person with a certain voice
    frequency even though there are many other sounds in the
    surrounding.

But imagine a situation in which the so called cocktail party effect
applies: having a conversation in a loud crowd at a party and listening
to your interlocutor you will immediately switch to listening to another
conversation if the content of it is semantically relevant to you, e.g.
if your name is mentioned.\
So it is found that filtering also happens semantically. The above
mentioned Shadowing Task was changed so that the semantic content of a
sentence was split up between the ears, and the subject, although
shadowing, was able to repeat the whole sentence because he or she was
following the semantic content unconsciously.\
Reacting to the effect of semantic filtering, new theories were
developed. Two important theories are the **Attenuation Theory**
(Treisman, 1964)`<ref>`{=html}Treisman, A. M. (1964). Monitoring and
storage of irrelevant messages and selective attention.

:   *Journal of Verbal Learning and Verbal Behaviour, 3*, 449-459.
    ```{=html}
    </ref>
    ```
    and the **Late Selection Theory** (Deutsch & Deutsch, 1963).[^3] The
    former proposes that we attenuate information which is less
    relevant, but do not filter it out completely. Thereby also semantic
    information of ignored frequencies can be analyzed but not as
    efficiently as those of the relevant frequencies. The Late Selection
    Theory presumes that all information is analyzed first and
    afterwards the decision of the importance of information is made.

Treisman and Geffen did an experiment to find out which one of the
theories holds. The experiment was a revision of the Shadowing Task.
Again the subjects have to shadow one ear but in contrast they also have
to pay attention to a certain sound which could appear on either ear. If
the sound occurs the subject has to react in a certain way (for example
knock on the table). The result is that the subject identifies the sound
on the shadowed ear in 87% of all cases and can only do this in 8% of
the cases on the ignored side. This shows that the information on the
ignored side must be attenuated since the rate of identification is
lower. If the Late Selection Theory were to hold then the subject would
have to analyze all information and would have to be able to identify
the same amount on the ignored side as on the shadowed side. Since this
is not the case the Attenuation Theory by Treisman explains the
empirical results more accurately.

framed\|center\|Illustration of the Attention Control Model by a)
Treisman - Attenuation Theory and b) Deutsch & Deutsch -- Late Selection
Theory.

## Short Term Memory

The **Short Term Memory** (STM) was initially discussed by Attkinson and
Shiffrin (1968).`<ref>`{=html}Atkinson, R. C. & Shiffrin, R. M. (1968).
Human memory: A proposed system and its control processes.

:   In K. Spence & J. Spence (Eds.), *The psychology of learning and
    motivation (Volume 2)*. New York: Academic Press.
    ```{=html}
    </ref>
    ```
    The Short Term Memory is the link between **Sensory Memory** and
    **Long Term Memory** (LTM). Later Baddeley proposed a more
    sophisticated approach and called the interface **Working Memory**
    (WM). We will first look at the classical Short Term Memory Model
    and then go on to the concept of Working Memory.

As the name suggests, information is retained in the Short Term Memory
for a rather short period of time (15--30 seconds). framed\|Short Term
Memory If we look up a phone
number in the phone book and hold it in mind long enough for dialling
the number, it is stored in the Short Term Memory. This is an example of
a piece of information which can be remembered for a short period of
time. According to George Miller (1956)`<ref>`{=html}Miller, G. A.
(1956). The magical number seven, plus or minus two: Some limits on our
capacity for processing information.

:   *Psychological Review, 63*, 81-97.
    ```{=html}
    </ref>
    ```
    the capacity of the Short Term Memory is five to nine pieces of
    information (The **magical number seven, plus or minus
    two**). The term \"pieces of
    information" or, as it is also called, **chunk** might strike one as
    a little vague.

All of the following are considered as chunks: single digits or letters,
whole words or even sentences and the like. It has been shown by
experiments also done by Miller that **chunking** (the process of
bundeling information) is a useful method to memorize more than just
single items in the common sense. Gobet et al. defined a chunk as \"a
collection of elements that are strongly associated with one another but
are weakly associated with other chunks\" (Goldstein, 2005).[^4] A very
intuitive example of chunking information is the following:\
Try to remember the following digits:

-   0 3 1 2 1 9 8 2

But you could also try another strategy to remember these digits:

-   03\. 12. 1982.

With this strategy you bundled eight pieces of information (eight
digits) to three pieces with help to remember them as a date schema.\
A famous experiment concerned with chunking was conducted by Chase and
Simon (1973)`<ref>`{=html}Chase, W. G. & Simon, H.A. (1973). The mind's
eye in chess. In W. G. Chase (Ed.), *Visual information processing*.

:   New York: Academic Press.
    ```{=html}
    </ref>
    ```
    with novices and experts in chess playing. When asked to remember
    certain arrangements of chess pieces on the board, the experts
    performed significantly better that the novices. However, if the
    pieces were arranged arbitrarily, i.e. not corresponding to possible
    game situations, both the experts and the novices performed equally
    poorly. The experienced chess players do not try to remember single
    positions of the figures in the correct game situation, but whole
    bundles of figures as already seen before in a game. In incorrect
    game situations this strategy cannot work which shows that chunking
    (as done by experienced chess players) enhances the performance only
    in specific memory tasks.

```{=html}
<!-- -->
```

From Short Term Memory to Baddeley's Working Memory Model:

Baddeley and Hitch (1974)`<ref>`{=html}Baddeley, A. D. & Hitch, G.
(1974). Working memory. In G. A. Bower (Ed.), *Recent advances in
learning and motivation (Vol. 8)*.

:   New York: Academic Press.
    ```{=html}
    </ref>
    ```
    drew attention to a problem with the Short Term Memory Model. Under
    certain conditions it seems to be possible to do two different tasks
    simultaneously, even though the STM, as suggested by Atkinson and
    Shiffrin, should be regarded as a single, undivided unit. An example
    for the performance of two tasks simultaneously would be the
    following: a person is asked to memorize four numbers and then read
    a text (unrelated to the first task). Most people are able to recall
    the four numbers correctly after the reading task, so apparently
    both memorizing numbers and reading a text carefully can be done at
    the same time. According to Baddeley and Hitch the result of this
    experiment indicates that the number-task and the reading-task are
    handled by two different components of Short Term Memory. So they
    coined the term \"Working Memory\" instead of \"Short Term Memory\"
    to indicate that this kind of Memory enables us to perform several
    cognitive operations at a time with different parts of the Working
    Memory.

## Working Memory

According to Baddeley, **Working Memory** is limited in its capacity
(the same limitations hold as for Short Term Memory) and the Working
Memory is not only capable of storage, but also of the manipulation of
incoming information. Working Memory consists of three parts:\
framed\|Working Memory

-   **Phonological Loop**
-   **Visuospatial Sketch Pad**
-   **Central Executive**

We will consider each module in turn:\
The **Phonological Loop** is responsible for auditory and verbal
information, such as phone numbers, people's names or general
understanding of what other people are talking about. We could roughly
say that it is a system specialized for language. This system can again
be subdivided into an active and a passive part. The storage of
information belongs to the passive part and fades after two seconds if
the information is not rehearsed explicitly. Rehearsal, on the other
hand, is regarded as the active part of the Phonological Loop. The
repetition of information deepens the memory. There are three well-known
phenomena that support the idea that the Phonological Loop is
specialized for language: The **phonological similarity effect**, the
**word-length effect** and **articulatory suppression**. When words that
sound similar are confused, we speak of the phonological similarity
effect. The word-length effect refers to the fact that it is more
difficult to memorize a list of long words and better results can be
achieved if a list of short words is memorized. Let us look at the
phenomenon of articulatory suppression in a little more detail. Consider
the following experiment:\
Participants are asked to memorize a list of words while saying \"the,
the, the \..." out loud. What we find is that, with respect to the
word-length effect, the difference in performance between lists of long
and short words is levelled out. Both lists are memorized equally
poorly. The explanation given by Baddeley et al. (1986),[^5] who
conducted this experiment, is that the constant repetition of the word
\"the\" prevents the rehearsal of the words in the lists, independent of
whether the list contains long or short words. The findings become even
more drastic if we compare the memory-performance in the following
experiment (also conducted by Baddeley and his co-workers in 1986):\
Participants were again asked to say out loud \"the, the, the \...\" But
instead of memorizing words from a list of short or long words, their
task was to remember words that were either spoken to them or shown to
them written on paper. The results indicated that the participants'
performances were significantly better if the words were presented to
them and not read out aloud. Baddeley concluded from this fact that the
performance in a memory task is improved if the two stimuli can be dealt
with in distinct components of the Working Memory. In other words, since
the reading of words is handled in the Visuospatial Sketch Pad, whereas
the saying of \"the\" belongs to the Phonological Loop, the two tasks do
not \"block\" each other. The rather bad performance of hearing words
while speaking could be explained by the fact that both hearing and
speaking are dealt with in the Phonological Loop and thus the two tasks
conflict with each other, decreasing the performance of memorization.\
In the **Visuospatial Sketch Pad**, visual and spatial information is
handled. This means that information about the position and properties
of objects can be stored. As we have seen above, performance decreases
if two tasks that are dealt with in the same component are to be done
simultaneously. Let us consider a further example that illustrates this
effect. Brandimonte and co-workers (1992)`<ref>`{=html}Brandimonte, M.
A., Hitch, G. J., & Bishop, D. V. M. (1992). Influence of short-term
memory codes on visual image processing:

:   Evidence from image transformation tasks. *Journal of Experimental
    Psychology: Learing, Memory, and Cognition, 18*, 157-165.
    ```{=html}
    </ref>
    ```
    conducted an experiment where participants were asked to say out
    loud \"la, la, la\..." At the same time they were given the task of
    subtracting a partial image from a given whole image. The
    subtraction had to be done mentally because the two images were
    presented only for a short time. The interesting result was that the
    performance not only didn\'t decrease while saying \"la, la, la
    \...\" when compared to doing the subtraction-task alone, but the
    performance even increased. According to Brandimonte this was due to
    the fact that the subtraction task was easier if handled in the
    Visuospatial Sketch Pad as opposed to the Phonological Loop (both
    the given and the resulting pictures were such that they could also
    be named, i.e. verbalized, a task that belongs to the Phonological
    Loop). As mentioned above, because of the fact that the subtraction
    of a partial image from a whole given image is easier if done
    visually, the performance increased if participants were forced to
    visually perform that task, i.e. if they were forced to use the
    component that is suited best for the given task. We have seen that
    the Phonological Loop and the Visuospatial Sketch Pad deal with
    rather different kinds of information which nonetheless have to
    somehow interact in order to do certain tasks. The component that
    connects those two systems is the Central Executive.

The **Central Executive** co-ordinates the activity of both the
Phonological Loop and the Visuospatial Sketch Pad. Imagine the following
situation: You are driving a car and your friend in the passenger seat
has the map and gives you directions. The directions are given verbally,
i.e. they are handled by the Phonological Loop, while the perception of
the traffic, street lights, etc. is obviously visual, i.e. dealt with in
the Visuospatial Sketch Pad. If you now try to follow the directions
given to you by your friend it is necessary to somehow combine both
kinds of information, the verbal and the visual information. This
important connection of the two components is done by the Central
Executive. It also links the Working Memory to Long Term Memory,
controls the storage in Long Term Memory and the retrieval from it. The
process of storage is influenced by the duration of holding information
in Working Memory and the amount of manipulation of the information. The
latter is stored for a longer time if it is semantically interpreted and
viewed with relation to other information already stored in Long Term
Memory. This is called Deep Processing. Pure syntactical processing
(reading a text for typos) is called Shallow Processing. Baddeley
proposes also further capabilities for the Central Executive:

-   **Initiating movement**
-   **Control of conscious attention**

Problems which arise with the Working Memory approach:

In theory, all information has to pass the Working Memory in order to be
stored in the Long Term Memory. However, cases have been reported where
patients could form Long Term Memories even though their STM-abilities
were severely reduced. This clearly poses a problem to the modal model
approach. It was suggested by Shallice and Warrington
(1970)`<ref>`{=html}Shallice, T., & Warrington, E. K. (1970).
Independent functioning of verbal memory stores: A neuropsychological
study.

:   *Quarterly Journal of Experimental Psychology,22*, 261-273.
    ```{=html}
    </ref>
    ```
    that there must be another possible way for information to enter
    Long Term Memory than via Working Memory.

## Long Term Memory

As the name already suggest, **Long Term Memory** is the system where
memories are stored for a long time. \"Long\" in this sense means
something between a few minutes and several years or even decades to
lifelong. framed\|Long Term
Memory Similar to Working Memory,
Long Term Memory can again be subdivided into different types. Two major
distinctions are made between **Declarative** (conscious) and
**Implicit** (unconscious) **Memory**. Those two subtypes are again
split into two components each: **Episodic** and **Semantic Memory**
with respect to **Declarative Memory** and **Priming Effects**, and
**Procedural Memory** with respect to Implicit Memory. In contrast to
Short Term or Working Memory, the capacity of Long Term Memory is
theoretically infinite. The opinions as to whether information remains
in the Long Term Memory forever or whether information can get deleted
differ. The main argument for the latter opinion is that apparently not
all information that was ever stored in LTM can be recalled. However,
theories that regard Long Term Memories as not being subject to deletion
emphasize that there might be a useful distinction between the existence
of information and the ability to retrieve or recall that information at
a given moment. There are several theories about the "forgetting" of
information. These will be covered in the section **"Forgetting and
False Memory"**.

#### Declarative Memory

Let us now consider the two types of **Declarative Memory**. As noted
above, those two types are **Episodic** and **Semantic Memory**.
Episodic Memory refers to memories for particular events that have been
experienced by somebody (autobiographical information). Typically, those
memories are connected to specific times and places. Semantic Memory, on
the other hand, refers to knowledge about the world that is not
connected to personal events. Vocabularies, concepts, numbers or facts
would be stored in the Semantic Memory. Another subtype of memories
stored in Semantic Memory is that of the so called **Scripts**. Scripts
are something like blueprints of what happens in a certain situation.
For example, what usually happens if you visit a restaurant (You get the
menu, you order your meal, eat it and you pay the bill). Semantic and
Episodic Memory are usually closely related to one another, i.e. memory
of facts might be enhanced by interaction with memory about personal
events and vice versa. For example, the answer to the factual question
of whether people put vinegar on their chips might be answered
positively by remembering the last time you saw someone eating fish and
chips. The other way around, good Semantic Memory about certain things,
such as football, can contribute to more detailed Episodic Memory of a
particular personal event, like watching a football match. A person that
barely knows the rules of that game will most probably have a less
specific memory for the personal event of watching the game than a
football-expert will.

#### Implicit Memory

We now turn to the two different types of **Implicit Memory**. As the
name suggests, both types are usually active when unconscious memories
are concerned. This becomes most evident for **Procedural Memory**,
though it must be said that the distinction between both types is not as
clearly cut as in the case of Declarative Memory and that often both
categories are collapsed into the single category of Procedural Memory.
But if we want to draw the distinction between **Priming Effects** and
**Procedural Memory**, the latter category is responsible for highly
skilled activities that can be performed without much conscious effort.
Examples would be the tying of shoelaces or the driving of a car, if
those activities have been practiced sufficiently. It is some kind of
movement plan. As regards the **Priming Effect**, consider the following
experiment conducted by Perfect and Askew (1994):[^6]\
Participants were asked to read a magazine without paying attention to
the advertisements. After that, different advertisements were presented
to them; some had occurred in the magazine, others had not. The
participants were told to rate the presented advertisement with respect
to different criteria such as how appealing, how memorable or
eye-catching they were. The result was that in general those
advertisements that had been in the magazine received higher rankings
than those that had not been in the magazine. Additionally, when asked
which advertisements the participants had actually seen in the magazine,
the recognition was very poor (only 2.8 of the 25 advertisements were
recognized). This experiment shows that the participants performed
**implicit learning** (as can be seen from the high rankings of
advertisements they had seen before) without being conscious of it (as
can be seen from the poor recognition rate). This is an example of the
Priming Effect.\
framed\|center\|Final overview of all different types of memory and
their interaction

# Forgetting and False Memory

As important as memory is, also the process of Forgetting is present to
everybody.\
Therefore one might wonder:

-   Why do we forget at all?
-   What do we forget?
-   How do we forget?

Why do we forget at all?

One might come up with something you could call "mental hygiene". It is
not useful to remember every little detail of your life and your
surrounding, but rather a disadvantage because you maybe would not be
able to remember the important things as quickly or even quick enough
but have an overload of facts in your memory. Therefore it is important
that unused memories are "cleaned up" so that only relevant information
is stored.

What do we forget and how?

There are different theories about how things are forgotten. One theory
proposes that the capacity of the Long Term Memory is infinite. This
would mean that actually all memories are stored in the LTM but some
information cannot be recalled (anymore) due to factors to be mentioned
in the following paragraphs:

There are two main theories about the causes of forgetting:

-   The _**Trace Decay Theory**_ states that you
    need to follow a certain path, or trace, to recall a memory. If this
    path has not been used for some time, one would say that the
    activity of the information decreases (it fades (-\>decays)), which
    leads to difficulty or the inability to recall the memory. !Memory
    Interference{width="450"}

```{=html}
<!-- -->
```
-   The **_Interference Theory_** proposes that
    all memories interfere with each other. One distinguishes between
    two kinds of interferences:
    -   **Proactive Interference**:

    :   Earlier memories influence new ones or hinder one to make new
        ones.

    -   **Retroactive Interference**:

    :   Old memories are changed by new ones, maybe even so much that
        the original one is completely 'lost'.

```{=html}
<!-- -->
```
-   Which of the two theories applies in your opinion?
-   Do you agree with a mixture of the two?

!Ebbinghaus Curve of
forgetting{width="450"}

In 1885 **Herrmann Ebbinghaus** did
several self-experiments to research human forgetting. He memorized a
list of meaningless syllables, like "WUB" and "ZOF", and tried to recall
as many as possible after certain intervals of time for several weeks.
He found out that forgetting can be described with an almost logarithmic
curve, the so called **forgetting
curve** which you can see on the left.

These theories about forgetting already make clear that memory is not a
reliable recorder but it is a construction based on what actually
happened plus additional influences, such as other knowledge,
experiences, and expectations. Thus **false memories** are easily
created.

In general there are three types of tendencies towards which people's
memories are changed. These tendencies are called

## Biases in memory

One distinguishes between three major types:

-   **Egocentric Bias**

    :   It makes one see his or herself in the best possible light.
-   **Consistency Bias**

    :   Because of which one perceives his or her basic attitudes to
        remain persistent over time.
-   **Positive Change Bias**

    :   It is cause for the fact that one perceives things to be
        generally improving.

(For a list of more known memory biases see: List of memory
biases)

There are moments in our lives that we are sure we will never forget. It
is generally perceived that the memories of events that we are
emotionally involved with are remembered for a longer time than others
and that we know every little detail of them. These kinds of memories
are called **Flashbulb Memories**.\
The accuracy of the memories is an illusion, though. The more time
passes, the more these memories have changed while our feeling of
certainty and accuracy increases. Examples for Flashbulb Memories are
one's wedding, the birth of one's child or tragedies like September
11th.

Interesting changes in memory can also occur due to **Misleading
Postevent Information** (MPI). After an event information given another
person can so to say intensify your memory in a certain respect. This
effect was shown in an experiment by Loftus and Palmer
(1974):`<ref>`{=html}Loftus, E. F., & Palmer, J. C. (1974).
Reconstruction of an automobile destruction:

:   An example of the interaction between language and memory. *Journal
    of Verbal Learning and Verbal Behavior, 13*, 585-589.
    ```{=html}
    </ref>
    ```

The subjects watched a film in which there were several car accidents.
Afterwards they were divided into three groups that were each questioned
differently. While the control group was not asked about the speed of
the cars at all, in the other groups questions with a certain key word
were posed. One group was asked how fast the cars were going when they
hit each other, while in the other question the verb "smashed" was used.
One week later all participants were asked whether they saw broken glass
in the films. Both the estimation of speed and the amount of people
claiming to have seen broken glass increased steadily from the control
group to the third group.\
Based on this **Misinformation Effect** the **Memory Impairment
Hypothesis** was proposed.\
This hypothesis states that suggestible and more detailed information
that one receives after having made the actual memory can replace the
old memory.\
Keeping the possible misleading information in mind, one can imagine how
easily eyewitness testimony
can be (purposely or accidentally) manipulated. Depending on which
questions the witnesses are asked they might later on remember to see,
for example, a weapon or not.

These kinds of changes in memory are present in everyone on a daily
basis. But there are other cases: People with a lesion in the brain
sometimes suffer from **Confabulation**. They construct absurd and
incomplete memories that can even contradict with other memories or with
what they know. Although the people might even be aware of the
absurdness of their memories they are still firmly convinced of them.
(See Helen Phillips\' article *Mind fiction: Why your brain tells tall
tales*)

## Repressed and Recovered Memories

If one cannot remember an event or detail, it does not mean that the
memory is completely lost. Instead one would say that these memories are
**repressed**, which means that they cannot easily be remembered. The
process of remembering in these cases is called **recovery**.\
Recovering of a repressed memory usually occurs due to a **retrieval
cue**. This might be an object or a scene that reminds one of something
which has happened long ago.\
Traumatic events, which happened during childhood for example, can be
recovered with the help of a therapist. This way, perpetrators have been
brought to trial after decades.\
Still, the correctness of the "recovered" memory is not guaranteed: as
we know, memory is not reliable and if the occurrence of an event is
suggestible one might produce a false memory.\
Look at the illustration to the right to be able to relate to these
processes.

!How did the memory for an event become what it
is?

Other than on a daily basis errors in memory and amnesia are due to
damages in the brain. The following paragraphs will present the most
important brain regions enabling memory and mention effects of damage to
them.

# Some neurobiological facts about memory

In this section, we will first consider how information is stored in
synapses and then talk about two regions of the brain that are mainly
involved in forming new memories, namely the **amygdala** and the
**hippocampus**. To show what effects memory diseases can have and how
they are classified, we will discuss a case study of **amnesia** and two
other common examples for amnesic diseases: **Karsakoff's amnesia** and
**Alzheimer's disease**.

## Information storage

The idea that physiological changes at synapses happen during learning
and memory was first introduced by **Donald Hebb**.[^7] It was in fact
shown that activity at a synapse leads to structural changes at the
synapse and to enhanced firing in the postsynaptic neuron. Since this
process of enhanced firing lasts for several days or weeks, we talk
about **Long Term Potentiation**
(LTP). During this process, existing synaptic proteins are altered and
new proteins are synthesized at the modified synapse. What does all this
have to do with memory? It has been discovered that LTP is most easily
generated in regions of the brain which are involved in learning and
memory - especially the hippocampus, about which we will talk in more
detail later. Donald Hebb found out that not only a synapse of two
neurons is involved in LTP but that a particular group of neurons is
more likely to fire together. According to this, an experience is
represented by the firing of this group of neurons. So it works
according to the principle: **"what wires together fires together"**.

## Amygdala

The **amygdala** is involved in the modulation
of **memory consolidation**. !Location of the amygdala in the human
brain Following
any learning event, the Long Term Memory for the event is not
instantaneously formed. Rather, information regarding the event is
slowly assimilated into long term storage over time, a process referred
to as **memory consolidation**,
until it reaches a relatively permanent state. During the consolidation
period, memory can be modulated. In particular, it appears that
emotional arousal following a learning event influences the strength of
the subsequent memory for that event. Greater emotional arousal
following a learning event enhances a person\'s retention of that event.
Experiments have shown that administration of stress hormones to
individuals, immediately after they learn something, enhances their
retention when they are tested two weeks later. The amygdala, especially
the basolateral nuclei, is involved in mediating the effects of
emotional arousal on the strength of the memory for the event. There
were experiments conducted by James
McGaugh on animals in special laboratories.
These laboratories have trained animals on a variety of learning tasks
and found that drugs injected into the amygdala after training affect
the animal's subsequent retention of the task. These tasks include basic
**Pavlovian Tasks** such as **Inhibitory
Avoidance**, where a rat learns to associate a mild footshock with a
particular compartment of an apparatus, and more complex tasks such as
spatial or cued water maze, where a rat learns to swim to a platform to
escape the water. If a drug that activates the amygdala is injected into
the amygdala, the animals had better memory for the training in the
task. When a drug that inactivated the amygdala was injected, the
animals had impaired memory for the task. Despite the importance of the
amygdala in modulating memory consolidation, however, learning can occur
without it, although such learning appears to be impaired, as in fear
conditioning impairments following amygdala damage. Evidence from work
with humans indicates a similar role of the amygdala in humans. Amygdala
activity at the time of encoding information correlates with retention
for that information. However, this correlation depends on the relative
\"emotionality\" of the information. More emotionally-arousing
information increases amygdalar activity, and that activity correlates
with retention.

## Hippocampus

Psychologists and neuroscientists dispute over the precise role of the
**hippocampus**, but, generally, agree that
it plays an essential role in the formation of new memories about
experienced events (Episodic or Autobiographical Memory). !Position of
the hippocampus in the human
brain{width="185"}
Some researchers prefer to consider the hippocampus as part of a larger
medial temporal lobe memory system
responsible for general declarative memory (memories that can be
explicitly verbalized --- these would include, for example, memory for
facts in addition to episodic memory). Some evidence supports the idea
that, although these forms of memory often last a lifetime, the
hippocampus ceases to play a crucial role in the retention of the memory
after a period of consolidation. Damage to the hippocampus usually
results in profound difficulties in forming new memories (anterograde
amnesia), and normally also affects access to memories prior to the
damage (retrograde amnesia). Although the retrograde effect normally
extends some years prior to the brain damage, in some cases older
memories remain intact - this sparing of older memories leads to the
idea that consolidation over time involves the transfer of memories out
of the hippocampus to other parts of the brain. However, researchers
have difficulties in testing the sparing of older memories and, in some
cases of retrograde amnesia, the sparing appears to affect memories
formed decades before the damage to the hippocampus occurred, so its
role in maintaining these older memories remains controversial.

\

## Amnesia

As already mentioned in the preceding section about the hippocampus,
there are two types of **amnesia** - **retrograde** and **antrograde
amnesia**. framed\|center\|Different types of
Amnesia Amnesia can occur when there
is damage to a number of regions in the medial temporal lobe and their
surrounding structures. The **patient H.M.** is
probably one of the best known patients who suffered from amnesia.
Removing his medial temporal lobes, including the hippocampus, seemed to
be a good way to treat the epilepsy. What could be observed after this
surgery was that H.M. was no longer able to remember things which
happened after his 16th birthday, which was 11 years before the surgery.
So given the definitions above one can say that he suffered retrograde
amnesia. Unfortunately, he was not able to learn new information due to
the fact that his hippocampus was also removed. H.M. therefore suffered
not only from retrograde amnesia, but also from anterograde amnesia. His
Implicit Memory, however, was still working. In procedural memory tests,
for example, he still performed well. When he was asked to draw a star
on a piece of paper which was shown to him in a mirror, he performed as
bad as every other participant in the beginning. But after some weeks
his performance improved even though he could not remember having done
the task many times before. Thus, H.M.'s Declarative Memory showed
severe deficits but his Implicit Memory was still fine. Another quite
common cause of amnesia is the **Korsakoff's
syndrome** or also called
Korsakoff's amnesia. Long term alcoholism usually elicits this
Korsakoff's amnesia due to a prolonged deficiency of vitamin B1. This
syndrome is associated with the pathology of the midline diencephalon
including the dorsomedial thalamus. **Alzheimer's
disease** is probably the best known type of
amnesia because it is the most common type in our society. Over 40
percent of the people who are older than 80 are affected by Alzheimer's
disease. It is a neurodegenerative disease and the region in the brain
which is most affected is the entorhinal cortex. This cortex forms the
main input and output of the hippocampus and so damages here are mostly
severe. Knowing that the hippocampus is especially involved in forming
new memories one can already guess the patients have difficulties in
learning new information. But in late stages of Alzheimer's disease also
retrograde amnesia and even other cognitive abilities, which we are not
going to discuss here, might occur.

center\|framed\|This figure shows the brain structures which are
involved in forming new memories

Final checklist of what you should keep in mind

------------------------------------------------------------------------

1.  Why does memory exist?
2.  What is sensory memory?
3.  What is the distinction between Short Term memory and Working
    Memory?
4.  What is Long Term Memory and which brain area(s) are involved in
    forming new memories?
5.  Remember the main results of the theory (For example: What does the
    Filter Theory show?)
6.  Don't forget why we forget!

# Links

-   Memory in
    Psychology,Encyclopedia
    of Psychology
-   Psychology 101 Memory and
    Forgetting, AllPsych
    ONLINE
-   Human Memory website of the University of
    Amsterdam

# References

```{=html}
<references/>
```
**Everyday memory - Eyewitness testimony**

**Introduction**

Witness psychology is the study of human as an observer and reporter of
events in life. It's about how detailed and accurate we register what is
happening, how well we remember what we observed, what causes us to
forget and remember the mistakes, and our ability to assess the
reliability and credibility of others\' stories. It is the study of
observation and memory for large and small events in life, from everyday
trivialities to the dramatic and traumatic events that shook our lives
(Magnussen, 2010)

**Basic concepts**

The eyewitness identification literature has developed a number of
definitions and concepts that require explanation. Each definition and
concept is described below.

A *lineup* is a procedure in which a criminal suspect (or a picture of
the suspect) is placed among other people (or pictures of other people)
and shown to an eyewitness to see if the witness will identify the
suspect as the culprit in question. The term suspect should not be
confused with the term culprit. A suspect might or might not be the
culprit, a suspect is suspected of being the culprit (Wells & Olson,
2003)

*Fillers* are people in the lineup who are not suspects. Fillers,
sometimes called foils or distractors, are known-innocent members of the
lineup. Therefore, the identification of filler would not result in
charges being brought against the filler. A culprit-absent lineup is one
in which an innocent suspect is embedded among fillers and a
culprit-present lineup is one in which a guilty suspect (culprit) is
embedded among fillers. The primary literature sometimes calls these
target-present and target-absent lineups (Wells & Olson, 2003).

A *simultaneous lineup* is one in which all lineup members are presented
to the eyewitness at once and is the most common lineup procedure in use
by law enforcement. A sequential lineup, on the other hand, is one in
which the witness is shown only one person at a time but with the
expectation that there are several lineup members to be shown (Wells &
Olson, 2003).

A *lineup's functional size* is the number of lineup members who are
"viable" choices for the eyewitness. For example, if the eyewitness
described the culprit as being a tall male with dark hair and the
suspect is the only lineup member who is tall with dark hair, then the
lineup's functional size would be 1.0 even if there were 10 fillers.
Today functional size is used generically to mean the number of lineup
members who fit the eyewitness's description of the culprit (Wells &
Olson, 2003).

*Mock witnesses* are people who did not actually witness the crime but
are asked to pick a person from the lineup based on the eyewitness's
verbal description of the culprit. They are shown the lineup and are
asked to indicate who is the offender. Mock witnesses are used to test
the functional size of the lineup (Wells & Olson, 2003).

The *diagnosticity of suspect identification* is the ratio of accurate
identification rate with a culprit-present lineup to the inaccurate
identification rate with a culprit- absent lineup. The diagnosticity of
"not there" is the ratio of "not there" response rates with
culprit-absent lineups to "not there" response rates with
culprit-present lineups. The diagnosticity of filler identifications is
the ratio of filler identification rates with culprit-absent lineups to
filler identification rates with culprit-present lineups (Wells & Olson,
2003)

Among variables that affect eyewitness identification accuracy, a system
variable is one that is, or could be, under control of the criminal
justice system, while an estimator variable is one that is not.
Estimator variables include lighting conditions at the time of
witnessing and whether the witness and culprit are of the same or of
different races. System variables include instructions given to
eyewitnesses prior to viewing a lineup and the functional size of a
lineup. The distinction between estimator and system variables has
assumed great significance in the eyewitness identification literature
since it was introduced in the late 1970s . In large part, the
prominence of this distinction attests to the applied nature of the
eyewitness identification literature. Whereas the development of a
literature on estimator variables permits some degree of post diction
that might be useful for assessing the chances of mistaken
identification after the fact, the development of a system variable
literature permits specification of how eyewitness identification errors
might be prevented in the first place (Wells & Olson, 2003).

**History and Reliability**

The criminal justice system relies heavily on eyewitness identification
for investigating and prosecuting crimes. Psychology has built the only
scientific literature on eyewitness identification and has warned the
justice system of problems with eyewitness identification evidence.
Recent DNA exoneration cases have corroborated the warnings of
eyewitness identification researchers by showing that mistaken
eyewitness identification was the largest single factor contributing to
the conviction of innocent people (Wells & Olson, 2003).

Psychological researchers who began programs in the 1970s, however, have
consistently articulated concerns about the accuracy of eyewitness
identification. Using various methodologies, such as filmed events and
live staged crimes, eyewitness researchers have noted that mistaken
identification rates can be surprisingly high and that eyewitnesses
often express certainty when they mistakenly select someone from a
lineup. Although their findings were quite compelling to the researchers
themselves, it was not until the late 1990s that criminal justice
personnel began taking the research seriously. This change in attitude
about the psychological literature on eyewitness identification arose
primarily from the development of forensic DNA tests in the 1990s (Wells
& Olson, 2003). More than 100 people who were convicted prior to the
advent of forensic DNA have now been exonerated by DNA tests, and more
than 75% of these people were victims of mistaken eyewitness. The
apparent prescience of the psychological literature regarding problems
with eyewitness identification has created a rising prominence of
eyewitness identification research in the criminal justice system.
Because most crimes do not include DNA-rich biological traces, reliance
on eyewitness identification for solving crimes has not been
significantly diminished by the development of forensic DNA tests. The
vast criminal justice system itself has never conducted an experiment on
eyewitness identification (Wells & Olson, 2003).

**Research**

The experimental method has dominated the eyewitness literature, and
most of the experiments are lab based. Lab-based experimental methods
for studying eyewitness issues have strengths and weaknesses. The
primary strength of experimental methods is that they are proficient at
establishing cause--effect relations. This is especially important for
research on system variables, because one needs to know in fact whether
a particular system manipulation is expected to cause better or worse
performance. In the real world, many variables can operate at the same
time and in interaction with one another (Wells, Memon & Penrod, 2006)

Multicollinearity can be quite a problem in archival/field research,
because it can be very difficult to sort out which (correlated)
variables are really responsible for observed effects. The control of
variables that is possible in experimental research can bring clarity to
causal relationships that are obscured in archival research. For
example, experiments on stress during witnessing have shown, quite
compellingly, that stress interferes with the ability of eyewitnesses to
identify a central person in a stressful situation. However, when Yuille
and Cutshall (1986) studied multiple witnesses to an actual shooting,
they found that those who reported higher stress had better memories for
details than did those who reported lower stress. Why the different
results? In the experimental setting, stress was manipulated while other
factors were held constant; in the actual shooting, those who were
closer to the incident reported higher levels of stress (presumably
because of their proximity) but also had a better view. Thus, in the
actual case, stress and view covaried. The experimental method is not
well suited to post diction with estimator variables---that is, there
may be limits to generalizing from experiments to actual cases. One
reason is that levels of estimator variables in experiments are fixed
and not necessarily fully representative of the values observed in
actual cases. In addition, it is not possible to include all interesting
and plausible interactions among variables in any single experiment (or
even in a modest number of experiments). Clearly, generalizations to
actual cases are best undertaken on the basis of a substantial body of
experimental research conducted across a wide variety of conditions and
employing a wide variety of variables. Nevertheless, the literature is
largely based on experiments due to a clear preference by eyewitness
researchers to learn about cause and effect. Furthermore, ''ground
truth'' (the actual facts of the witnessed event) is readily established
in experiments, because the witnessed events are creations of the
experimenters. This kind of ground truth is difficult, if not
impossible, to establish when analyzing actual cases (Wells et al.
2006).

**Memory**

The world is complex. All natural situations or scenes contains
infinitely more physical and social information than the brain is able
to detect. The brain's ability to record information is limited. In
studies of immediate memory for strings of numbers that have been read
once, it turns out that most people begin to go wrong if the number of
single digits exceeds five (Nordby, Raanaas & Magnussen, 2002). The
limitations of what humans are capable to process, leads to an
automatically selection of information. This selection is partially
controlled by external factors, the factors in our environment that
captures our attention (Magnussen, 2010). In the witness psychology we
often talk about the weapon focus, in which eyewitnesses attend to the
weapon, which reduces their memory for other information (Eysenck &
Keane, 2010). The selection of information in a cognitive overload
situation is also governed by psychological factors, the characteristics
of the person who is observing. It is about the emotional state and the
explicit and implicit expectations of what will happen. Psychologists
call such expectations cognitive schemas. Cognitive schemas forms a sort
of hypotheses or map of the world based on past experiences. These
hypotheses or mental maps of the world determines what the brain chooses
of the information, and how it interprets and if it will be remembered.
When information is uncertain or ambiguous, the psychological factors
are strong (Magnussen, 2010).

Eyewitness testimony can be distorted via confirmation bias, i.e., event
memory is influenced by the observer's expectation. A study made by
Lindholm and Christianson (1998), Swedish and immigrant students saw a
videotaped simulated robbery in which the perpetrator seriously wounded
a cashier with a knife. After watching the video, participants were
shown color photographs of eight men -- four Swedes and the remainder
immigrants. Both Swedish and immigrant participants were twice as likely
to select an innocent immigrant as an innocent swede. Immigrants are
overrepresented in Swedish crime statistics, and this influenced
participants' expectations concerning the likely ethnicity of the
criminal (Eysenck & Keane, 2010)

Bartlett (1932) explained why our memory is influenced by our
expectations. He argued that we possess numerous schemas or packets of
knowledge stored in long-term memory. These schemas lead us to form a
certain expectations and can distort our memory by causing us to
reconstruct an event details based on "what must have been true"(Eysenck
& Keane, 2010). What we select of information, and how we interpret
information is partially controlled by cognitive schemas. Many cognitive
schemas are generalized, and for a large automated and non-conscious, as
the expectation that the world around us is stable and does not change
spontaneously. Such generalized expectations are basic economic and
making sure we do not have to devote so much energy to monitor the
routine events of daily life, but they also contribute to the fact that
we in certain situations may overlook important, but unexpected
information, or supplement the memory with details who is form
consistent, but who actually don´t exist (Magnussen, 2010).

**Estimator variables**

First, estimator variables are central to our understanding of when and
why eyewitnesses are most likely to make errors. Informing police,
prosecutors, judges, and juries about the conditions that can affect the
accuracy of an eyewitness account is important. Second, our
understanding of the importance of any given system variable is, at
least at the extreme, dependent on levels of the estimator variables.
Consider a case in which a victim eyewitness is abducted and held for 48
hours by an unmasked perpetrator; the witness has repeated viewings of
the perpetrator, lighting is good, and so on. We have every reason to
believe that this witness has a deep and lasting memory of the
perpetrator's face. Then, within hours of being released, the eyewitness
views a lineup. Under these conditions, we would not expect system
variables to have much impact. For instance, a lineup that is biased
against an innocent suspect is not likely to lead this eyewitness to
choose the innocent person, because her memory is too strong to be
influenced by lineup bias. On the other hand, when an eyewitness's
memory is weaker, system variables have a stronger impact. Psychologists
have investigated the effects on identification accuracy of a large
number of estimator variables, witness, crime, and perpetrator
characteristics. Here we recount findings concerning several variables
that have received significant research attention and achieved high
levels of consensus among experts (based on items represented in a
survey by Kassin, Tubb, Hosch, & Memon, 2001) or have been the subject
of interesting recent research (Wells et al. 2006).

**References**

Eysenck, M.E., & Keane, M.T., (2010). Cognitive psychology. A student´s
Handbook (6th Edn). New York: Psychological Press

Magnussen, S., (2010). Vitnepsykologi. Pålitelighet og troverdighet I
dagligliv og rettssal. Oslo: Abstrakt forlag as.

Nordby, K., Raanaas, R.K. & Magnussen, S. (2002). The expanding
telephone number. I: Keying briefly presented multiple-digit numbers.
Behavior and Information Technology, 21, 27-38.

Wells, G.L., Memon, A., & Penrod, S.D. ( 2006). Eyewitness Evidence.
Improving Its Probative Value, 7(2), 45-75.

Wells, G.L., & Olson, E.A., (2003). Eyewitness Testimony, 54:277-95.
Doi: 10.1146/annurev.psych.54.101601.145028


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