Perception, Memory, Consciousness and Sleep

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17 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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Perception, Memory, Consciousness
and Sleep

Saad Almoshawah Ph.D

Perception


Perception is all about how we interpret the information
that we receive through the sense organs of the body.



Information which is received directly from the sense
organs is known as

sensation.

It is the actual sensory
impressions that we experience.



But if we are to make any sense out of our sensory
experiences, if they are to be something more than a
tumbled blur of colour, sound, or smells, then we need to
interpret them.



Perception



In visual perception (vision is the sense that psychologists
have studied in most depth) we need to be able to
distinguish objects from their backgrounds; we need to be
able to tell whether one object is further away than another
one; we need to be able to recognise familiar patterns and
faces, and so on. The psychological study of perception
consists of investigations of how we go about this, and
theories which psychologists have developed to explain it.


Attention is not the same as perception, but it is very
closely linked to it.


Perceiving objects and backgrounds


The first step in interpreting sensory information is to organise
it.


Perceptual organisation involves converting our impressions of
light, dark and colour into meaningful units which can represent
the world around us.


The first step in this process is to be able to distinguish objects
and figures from backgrounds. The way that we do this has been
studied by psychologists for many decades.



Distinguishing figures from backgrounds is very basic to
perception. It is so basic, in fact, that we will try to do it even if
the figures are not 'really' there. If we are faced with a mass of
confusing sensory information, we try to group together
different stimuli so that we can detect patterns.


The Gestalt laws of perception


During the
1930
s, the Gestalt psychologists investigated
how we go about perceiving objects and figures. They
identified a set of principles of perception, which they

referred to as the

laws of Pragnanz.

Pragnanz has the
same linguistic origin as our word 'pregnant', and it means
'loaded with meaning'.



The Gestalt laws of Pragnanz show how we attribute
meaning of some sort even to the most simple collections
of visual stimuli. There are four of them altogether.


The first is the

principle of similarity.

According to this
principle, if we look at a set of stimuli, and if none of the
other Gestalt laws apply, then we will automatically group
similar ones together
.


But this is easily overtaken by the second principle: the

principle of proximity.

According to this principle,
stimuli which are close to each other will be seen as
forming a group, even if they are not particularly similar



The third, and perhaps the strongest of the Gestalt
principles of perception, is known as the

principle of
closure.

Broadly speaking, it is that we have a strong
tendency to prefer closed figures rather than fragmented or
unconnected lines . This principle is so strong that it can
override all of the others .


And the fourth Gestalt law is the

principle of good
Gestalt.

This affects our perception, in the form of a
preference for figures which appear to be well rounded or
symmetrical, rather than ones that seem fragmented or
messy.







Face recognition



One area of research which forms an interesting link
between top
-
down and bottom
-
up theories of perception is
the study of how we go about recognising faces.



Recognising people from their faces is something that we
do quite automatically, yet when researchers analyse it,
they find that it actually involves a number of very
complex tasks. For instance, we can recognise the same
person several years later, when their facial features have
become changed with age; and we have no difficulty in
recognizing the same face even though it may be showing
wildly different emotional expressions


Face recognition


In general terms, it seems that we rely more on features
from the upper part of the face, like hair or eyes



When we are recognising faces that are familiar to us, we
seem to use a combination of descriptive cues. Some of
these are about the particular features of the face itself,
such as the colour of the eyes or the shape of the mouth,
while others are about the spacing between the different
features.



Face recognition


Ellis, Shepherd and Davies (
1979
) found that
when we are recognising familiar faces, we tend to
concentrate more on the internal features of a face,
like eyes, nose and mouth.


When we are recognising unfamiliar faces,
though, we concentrate more on external features
like hair and chin. In fact, it seems as though we
recognise familiar and unfamiliar faces in
completely different ways, involving different
cognitive mechanisms.


Face recognition units


Bruce and Young (
1986
) explored the implications of this,
and other evidence, and suggested that we develop a

face
recognition unit

for identifying people that we know.


Faces of strangers do not have recognition units, and so
when we are recognising those, we have to fall back on
descriptive criteria, such as hair colour, to know whether
we have seen that face (or a picture of it) before.



This could also explain why we do not usually notice
facial resemblances between our friends, although we often
notice strangers who look like people that we know.


Face recognition units


We have a special recognition unit for each friend, so their
faces only stimulate their own unit. But the faces of
strangers can trigger off other recognition units because
they do not have one of their own.


Recognising faces and remembering names


A face recognition unit of this kind includes deeper
knowledge about that person, and perhaps also our own
feelings about them, such as whether we liked or disliked

them. This is

semantic information
-

in other words, it is
meaningful information about how the stimulus actually
affects us.


Memory


We use memory all the time, in everyday living as well as

when we are studying. Think of the last time that you

decided to travel, try to remember every single moment


Memory research has a long and important history within
psychology. One of the first researchers into memory was
the introspectionist psychologist Herman Ebbinghaus
(
1885
) who established a tradition of meticulous work in
studying psychology as an experimental topic in the
laboratory. His work established a methodology and
approach which was highly influential in memory research
right through to the
1970
s.


Memory


from
1932
onwards, a different tradition in memory
research also emerged, originating with the work of Sir
Frederick Bartlett. Bartlett studied how people make sense
of the information that they receive, and how their personal
values and ideas affect what they remember.


This approach to 'real
-
life' memory also had its impact,
eventually leading to a new emphasis on research into
everyday memory in recent years.

The Three Processes in Memory: Encoding. Storage,

and Retrieval


What three processes are involved in the act of
remembering?


What must occur to enable us to remember a friend's name,
a fact from history, or an incident from our past? The act of
remembering requires the successful completion of three
processes:
encoding, storage, and retrieval
.


The first process,

encoding,

involves transforming
information into a form that can be stored in memory.
Sometimes we encode information automatically, without
any effort, but often we must do something with the
information in order to remember it

The Three Processes in Memory: Encoding. Storage,

and Retrieval


For example, if you met someone named Omer at school,
you might associate his name with your brother or best pal.
Such simple associations, as you will see, can markedly
improve your ability to recall names and other information.
The careful encoding of information greatly increases the
chance that you will remember it.


The second process in memory, storage, involves keeping
or maintaining information in memory. In order for the
encoded information to be stored, some physiological
change in the brain must take place a process called

consolidation.


The Three Processes in Memory: Encoding. Storage,

and Retrieval


Consolidation occurs automatically under normal
circumstances, but if a person loses consciousness for any
reason, the process can be disrupted and a permanent
memory will not form (Deutsch & Deutsch,
1966
). That is
why it is not unusual for a person who has been in a
serious car accident to awaken in a hospital and not
remember what has happened.

The Three Processes in Memory: Encoding. Storage,

and Retrieval


The final process,

retrieval,

occurs when information
stored in memory is brought to mind. Calling Omer by
name the next time you meet him shows that you have
retrieved his name from memory. To remember, we must
perform all three of these processes encode the
information, store it, and then retrieve it.


Memory failure can result from the failure of any one of
the three processes



Memory storage


Once the information has been encoded, it needs to be
stored. A number of different explanations have been put
forward to explain how this happens, and how memory is
structured.


The first is the two
-
process theory of memory, which is
also sometimes called the

structural model

of memory
(short
-
term memory STM and long term memoryLTM).


The second was put forward as a challenge to the structural
model, and is known as the

levels of processing

approach.


The third is the

working memory

model which provides
an alternative to the idea of short
-
term memory storage.



Theories of forgetting


The past hundred years of memory research have seen
several psychological explanations for forgetting.


Some theories about forgetting have been very specific,
concerning the decay of the memory trace; brain damage
or disease; motivated forgetting; or interference from other
material.


The reasons why we forget are to do with other
characteristics of memory.



There is a considerable amount of work, for instance,
which shows how important context, cues and processing
are for remembering; and so forgetting can sometimes be
seen as arising from inadequacy in this respect
.


Decay of the memory trace


One of the earliest ideas about memory storage was that
each remembered item would leave a kind of physiological
memory trace' in the brain, known as an

engram.



Unless this engram was strengthened by rehearsal, it would
gradually become weaker until it eventually decayed
altogether through lack of use. Recalling or recognising the
item again would 'refresh' the engram. So memories which
were not used would die away, and those which were
called to mind frequently would be strong
.


This theory of forgetting is a plausible one, which fits

with our subjective experience. But, in fact, it is almost

impossible to test it out
-

we cannot possibly know if a

memory exists unless we try to use it, and the act of doing

that would presumably strengthen the engram. We also

have the problem of constructive memory: as we will see, a

person who is trying to remember something can

unconsciously produce a plausible reconstruction, instead

of a 'real' memory, and we would not be able to tell the

difference.

Brain damage or disease


There are several different ways that
amnesia

can happen,

ranging from brain damage or head injuries to problems

arising through ageing.



It is also difficult to be sure that a problem really is some
form of amnesia.


Talland (
1968
) showed how most people have failures of
memory in normal life, so it is important not to confuse
normal forgetting with a memory disorder.

Brain damage or disease


Post
-
traumatic amnesia

is the kind of amnesia which

follows a severe blow or wound to the head. This can often

result in the loss of memory for the few minutes leading up

to the accident.


Being unable to remember things that have happened in

the past is known as

retrograde amnesia.



anterograde amnesia,
this is where the individual is
unable to store new memories, even though they may
retain their memories from before the damage was done.


Brain damage or disease


Milner (
1966
) described a patient, H.M., who experienced

anterograde amnesia

as a result of brain surgery in which
both sides of the hippocampus were removed. After the
operation, H.M. found himself to be unable to retain new
information, although he could still remember things that
he knew before.


Korsakoff's syndrome

is one of the most common

sources of anterograde amnesia. It develops in long
-
term

alcoholics, who have been drinking heavily and not eating

well for many years. This produces a thiamine deficiency

which eventually results in the person becoming unable to

store new memories.



Brain damage or disease


People with Korsakoff's syndrome often become highly
skilled at maintaining conversations by making general
remarks; so it is often difficult to realise how badly their
memory is damaged.


But sometimes it is so severe that the person cannot recall
someone that they have met only that morning, if they
meet them later in the same day.

Consciousness


One of the distinctive features of human beings, so it is
claimed, is that we are aware of our own consciousness.
But trying to identify and classify consciousness is not
easy.


We are continually experiencing changes in
consciousness. we have all experienced how different
moods can affect how we see the world.


we have all experienced the changes in consciousness
brought about when we are sleeping; and most of us have
experienced the changes in consciousness brought about
by at least some drugs, if only the use of caffeine to help
us wake up in the morning. In many ways.


Consciousness


consciousness is one of the most mystical of all human
attributes or at least, there has been a great deal of mystical
writing about it.


In the early days of psychology, consciousness was
regarded as the core of the discipline.


The

introspectionist
psychologists regarded the study of
the mind as the key to understanding everything about
people, and they believed that the careful analysis of
conscious experience would allow them to discover the
workings of the mind.

Consciousness


consciousness idea was challenged by a number of
theoretical developments, and in particular the two
opposing ideas

of psychoanalysis

and

behaviourism.



The Freudian idea that much of the mind's operation is
unconscious, taking place without the individual being
aware of it, questioned the idea that the contents of
consciousness can be reached by introspection; and the
behaviourist insistence that human behaviour could be seen
as the result of stimulus
-
response conditioning questioned
the importance of the concept of consciousness in an even
more fundamental way.

Consciousness


In more recent times, psychologists have grown away from
the behaviourist's total rejection of the idea of
consciousness, and there have been a number of attempts
to investigate it.


Consciousness appears to serve an important function in
allowing us to choose our actions. By weighing up a
situation we can select what we would like to do.



Consciousness also helps us to change or modify our
behaviour, if we find that we are acting inappropriately.
But identifying what it actually is, presents us with
considerable challenges.

Psychoactive drugs and

consciousness


Psychoactive drugs are drugs which affect an individual's
mental state: they may directly change our moods or how
we respond to the environment.


In general, psychoactive drugs produce their effects
because they affect the way that neurones communicate
with one another at the synapse.


Sedatives and depressants


The most commonly used sedative drug is undoubtedly the
drug alcohol. Like caffeine, alcohol is a very powerful
drug which we often overlook because it is in everyday
use.


Psychoactive drugs and

consciousness


Many people, for instance, believe that they can drive
adequately even when under the influence of the drug,
although when they are tested on a driving course even
very small amounts of alcohol result in many
misjudgements.


The widely used recreational drug

marijuana

is also a
depressant drug, which slows reaction time and induces
drowsiness. It was used as a tranquilliser during the

nineteenth century, and for over two thousand years in
China and on the Indian subcontinent, although owing to
the development of more specific drugs, it is no longer
used medically in the Western world
.

Sleep


Part of the study of consciousness includes the study of
sleep and dreaming. Sleep raises a number of questions.



What is going on when we are asleep? Why do our bodies
need to have these regular periods when normal everyday
behaviour seems to be turned off, and we remain quiescent
for hours on end? What happens when we do not get
enough sleep? And why do we dream?


Researchers have been investigating the phenomenon of
sleep throughout the second half of this century, looking at
the physiology of sleep, and at sleep cycles, at how it is
controlled by the brain, and at what happens when we
dream


Rhythms of sleep


As well as being part of our behavioural circadian rhythms,
sleep has its own internal rhythms.


We are aware of some of the general changes which
happen when we sleep.


The muscles become flaccid, the 'attention
-
monitoring'
systems of the brain seem to shut down, and we experience
a lengthy period of passivity and inaction. But that is not
all that is going on.


Dement and Kleitman also showed that, during the course
of the night, we pass through the different levels of sleep
several times, moving from higher to lower levels of sleep,
and back to higher levels again.


They argued that this cycle is repeated several times during
a typical night, although the deeper levels of sleep tend to
be reached only during the first few cycles.


Towards the end of the night, sleep cycles become
shallower, which Dement and Kleitman interpreted as the
person being more liable to wake up. Their conclusion,
then, was that the changes in EEG pattern reflected how
deeply the person was asleep.

Sleep
-
deprivation studies


People can do without sleep for very long periods of time,
and often manage surprisingly well on most tests of
psychological and physical functioning.



But this does not mean that sleep deprivation has no
effect: there are other, more general, consequences which
seem to result.


One of the problems seems to be that people who are
seriously sleep deprived can often rouse themselves
successfully for short
-
term tasks, but find themselves
losing awareness when undertaking routine or repetitive
activities.


They are able to do the kinds of controlled tasks which
provide experimenters with precise measurements, like
reaction time exercises or decision
-
making simulations


Sleep disorders


There are a number of abnormalities of sleep, which can
result in considerable discomfort for someone who is
experiencing them.


Perhaps the best known of these is the sleep disorder
known as

insomnia,

in which people experience difficulty
getting to sleep or remaining asleep.



Insomnia can arise for many reasons, but is frequently
associated with physiological states of anxiety and tension.



Dreaming


Everybody dreams during the course of the night, although
some people claim that they never do. This seems to be
because they have no recollection of having dreamed when
they wake up.


Dreams, as we know, are fascinating things, and
explaining dreaming has been a major preoccupation of
human cultures for as far back as we can possibly know.



Saudi Culture of dreaming, did we believe in dream?


Open issue of dream.