What is cognitive psychology? - Education Scotland

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NATIONAL QUALIFICATIONS CURRICULUM SUPPORT





Psychology


Cognitive Psychology


Staff Resource Pack




[ADVANCED HIGHER]



Gerard Keegan

Kilmarnock College








































Acknowledgements

This document is produced by Learning and Te
aching Scotland as part of the National
Qualifications support programme for Psychology. Original drawings are acknowledged
with thanks to Douglas McConnach.


First published 2003

Electronic version 2003


© Learning and Teaching Scotland 2003


This public
ation may be reproduced in whole or in part for educational purposes by
educational establishments in Scotland provided that no profit accrues at any stage.


THE THEORY OF PERFEC
T COMPETITION



CONTENTS



Section 1:

Guidance for tutors

1



Introduction

1


Statement of standards

2


Approache
s to learning and teaching

4


How to use this pack

6


Recording student attainment

7


Guidance on the content and context for this unit

8


Guidance on learning and teaching approaches for



this unit

8


Guidance on approaches to assessment for this unit

9


Section 2:

Student materials

11



What is cognitive psychology? Setting the scene



Outcomes 1 and 2: The concepts




Perception

23



Attention

72


Section 3:


Student materials (continued)




Outcome 3: Issues




The use of non
-
human animals in researc
h

91


Section 4:


General references

101





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COGNI TIVE PSYCHOLOGY

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GUIDANCE FOR TUTORS

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© Learni ng and Teachi ng Scot l and 2003

SECTION 1



Introduction


This is an optional component unit of Advanced Higher Psychology. It has a
value of one credit at Advanced Higher.



Unit content


The unit has three outcomes:


1.

Analyse major t
heories in cognitive psychology.

2.

Evaluate research evidence relating to theories in cognitive psychology.

3.

Analyse an issue in cognitive psychology.



Content of this pack


This pack contains resources that will assist the tutor with the delivery of t
his
unit. It contains material relevant to all of the outcomes.


Core skills


Details on core skills are obtainable from the Scottish Qualifications
Authority (SQA).



GUIDANCE FOR TUTORS

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© Learni ng and Teachi ng Scot l and 2003

Statement of standards


Outcome 1

Analyse major theories in cognitive psychology.


Per
formance criteria

(a)

Competing theoretical explanations in cognitive psychology are
explained accurately and comprehensively.

(b)

Competing theoretical explanations in cognitive psychology are
compared accurately in terms of their main features.

(c)

Compe
ting theoretical explanations in cognitive psychology are
contrasted accurately in terms of their main features.


Evidence requirements

To demonstrate satisfactory attainment of this outcome, candidates should
produce written or oral responses to cover all

performance criteria. They are
required to do so for
two

key concepts chosen from the following: perception,
attention, memory, language and thinking.


Written/oral responses will typically be extended responses of about 1,000
words for
each

key concept a
nd associated research evidence, integrating
Outcomes 1 and 2.


Outcome 2

Evaluate research evidence relating to theories in cognitive psychology.


Performance criteria

(a)

Research evidence relating to theories in cognitive psychology is
described accurat
ely.

(b)

Research evidence relating to theories in cognitive psychology is
explained clearly and accurately in terms of its strength of support for
the theories.

(c)

Validity of conclusions based on this research evidence is explained
clearly and accuratel
y.


Evidence requirements

To

demonstrate satisfactory attainment of this outcome, candidates should
produce written or oral responses to cover all performance criteria. They are
required to do so for research evidence in
two

key concepts chosen from the
fo
llowing: perception, attention, memory, language and thinking.

GUIDANCE FOR TUTORS

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3


© Learni ng and Teachi ng Scot l and 2003

Written/oral responses will typically be extended responses of about 1,000
words for
each
key

concept and associated research evidence, integrating
Outcomes 1 and 2.


Outcome 3

Analyse an issu
e in cognitive psychology.


Performance criteria

(a)

An issue relevant to cognitive psychology is explained clearly and
accurately.

(b)

Essential arguments of this issue are explained accurately and
comprehensively in a balanced way.

(c)

The contribution o
f this issue to cognitive psychology is explained
accurately and comprehensively.


Evidence requirements

To demonstrate satisfactory attainment of this outcome, candidates should
produce written or oral responses to cover all performance criteria. They are

required to do so for
one
issue from the following: science in cognition,
animals in research, representations, and computer modelling in cognitive
psychology or false memory.


Written/oral responses will typically be an extended response of about 1,000
words.


GUIDANCE FOR TUTORS

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© Learni ng and Teachi ng Scot l and 2003

Approaches to learning and teaching


In

delivering these units, it is useful if tutors achieve a balance between tutor
exposition and experiential learning. It is important to recognise that learners
acquire and process information in a number of
ways to help them learn.
These include visually, aurally, in discussion or exchange with others, during
group
-
based problem solving activities, and during solitary reflection.


Students should be encouraged from the beginning to draw on their own
experienc
es, perceptions, and their previous and current learning. Personal
experience of interacting with a range of people, and in a number of different
situations is an invaluable source of knowledge and is highly relevant to
cognitive psychology. The sharing of

experiences and insights will promote
general awareness that cognitive psychology assists self
-
understanding and an
understanding of humans in a variety of contexts.


Students should also be encouraged to gather and use information about
different people’
s actions, thoughts and feelings and to consider how these
affect themselves and others. Relevant quality newspaper and/or magazine
articles and video/film productions are useful resources, which bring
cognitive psychology to life, so that it can be shared

by comparatively large
groups of people at any one time. This remains appropriate even when the
material is fictional, provided it presents us with a true picture of the human
condition and is not deliberately sensationalised.


In delivering this unit, it

is appropriate that a multicultural approach is taken
since the learning needs of individuals vary according to their cultural
background. Case studies, role
-
play and simulations should incorporate
characters and elements from different social and cultura
l backgrounds
wherever possible.


Unit induction


At the beginning of the unit ‘Cognitive Psychology’, tutors should ensure that
students are clear about its nature and purpose. Induction for this unit should
last about two hours and should include an intr
oduction to the content of the
unit, provide a programme of work and explain the arrangements for
assessment and reassessment. At this point students can be given the
Candidates’ Guide from the Unit Assessment Pack. This helps explain what
the unit is abou
t and how it is assessed.


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© Learni ng and Teachi ng Scot l and 2003

In order to allow students to make a confident start, reference should be made
to links with previous or other current learning with which they are familiar.
It is also important to discuss and explore the nature of the course o
r group
award being undertaken by the group if appropriate.


It may be necessary to include induction exercises, particularly if the group is
a new one. The type and number of exercises used will, however, depend on
the nature of the particular group, thei
r familiarity with each other and with
the tutor involved.


Learning environment


The expertise of the tutor is invaluable in developing skills in, approaches to,
and insights about the subject of cognitive psychology. Tutors should aim to
create a relaxed

and enjoyable learning environment, which is both
motivating and supportive.


In order that a people perspective is always present the following conditions
should be met:




the provision of a learning climate in which students feel supported and
able to
express their thoughts and ideas;



a teaching style that promotes a supportive learning climate;



learning and teaching methods which draw on students’ past and present
learning experience and which enable them to integrate new ideas and
skills during th
eir interactions with others.


Further guidance can be found in the Psychology Subject Guide.



GUIDANCE FOR TUTORS

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How to use this pack


Purpose of the pack


This pack is designed to provide guidance and support materials to help tutors
in the delivery of the unit. The stud
ent information and activities are designed
to be used by tutors in the way that suits their preferred style of delivery and
the needs of their particular student group.


This pack has not been designed for open learning purposes.
Additional
reading, exerc
ises, assignments, etc. and answers to enclosed exercises and
worksheets will be provided and facilitated by the tutor. The student
activities in the pack will require to be followed up and brought together by
the tutor in whatever way is most appropriate.


The student activities in this pack cover the three outcomes and their
performance criteria at Advanced Higher level. The unit in the
learning/teaching situation calls for
two

key concepts
, their
features

and
explanations

and
one

issue

to be covered. Thi
s Staff Resource Pack
endeavours to cover
two

key concepts, their features and explanations, and
one

issue.


The material is presented in such a way that for each concept covered in these
support notes (
perception

and
attention
) Outcome 1 (Analyse major t
heories
in cognitive psychology) is discussed first. Outcome 2 (Evaluate research
evidence relating to [
these
1
] theories in cognitive psychology) is discussed
second and Outcome 3 (Analyse an issue in cognitive psychology) is dealt
with last. Section 3 wil
l deal with the issue in relation to cognitive
psychology being
the use of non
-
human animals in research
.


This sequence of delivery is by no means compulsory and may be rearranged
at the discretion of the tutor responsible for delivering the unit.


GUIDANCE FOR TUTORS

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© Learni ng and Teachi ng Scot l and 2003

Using

the materials


Useful learning materials in this pack include:




Information



Student activities
or



Interactives


All impinge on essential knowledge required for

this unit.

They are

particularly useful as handout material. They could also be used as
the focus
of input by the tutor and to develop ideas further as part of question
-
and
-
answer sessions and group discussions.


These information sheets can be photocopied as a separate pack, should the
tutor prefer to use them either as teaching notes or as
separate handout
materials. Alternatively, the materials could be assembled into smaller topic
packs.


All worksheets, assignments, exercises and group activities have been
covered on those pages that include a
Student Activity
or

Interactive
. These
genera
l activities have been developed to include exercises for individuals,
pairs, triads and small groups to conduct. Tutors may well wish to alter the
way in which these activities are carried out according to the needs of their
particular group.



Recording
student attainment


A

recording proforma for tutors to complete for individual candidate
attainment is available in the Unit Assessment pack.




Candidate’s record of progress


for individual candidates to have a record
of their attainment.



Internal Ass
essment Record


to record the internal assessment results of
the whole student group.


Tutors may devise their own alternative system for recording student
attainment.


GUIDANCE FOR TUTORS

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© Learni ng and Teachi ng Scot l and 2003

Guidance on the content and context for this unit


By introducing students to a range

of concepts and associated theories,
research evidence and issues in cognitive psychology, it is intended to
develop knowledge and understanding of cognitive psychology generally and
to emphasise the significance of this area to the whole of psychology.


A choice of two concepts and one issue is a feature of this unit. This provides
flexibility for centres to accommodate different needs and interests in
studying cognitive psychology at this level.


Fuller information on the content of this unit is provided

in the course details.



Guidance on learning and teaching approaches for this unit


General proposals regarding approaches to learning and teaching are
contained in the course details. Learning and teaching approaches should be
carefully selected to supp
ort the development of knowledge and
understanding, investigation and application. The learning experience at this
level should be interesting, to encourage enthusiasm for the subject and to
stimulate and prepare candidates for independent study.


The unit

should be approached using a wide range of stimulus materials and
teaching approaches. Candidates should be encouraged to draw upon their
own experiences and should have access to resources. The material should be
up
-
to
-
date and relevant to the unit, the
level of study and the interests of the
candidates. The emphasis throughout should be on active learning, whether as
part of a whole class, in small groups or as individuals. The outcomes are
interconnected and should be approached as such. Especially at A
dvanced
Higher
it is recommended that, wherever possible, outcomes should be
covered in an integrated way
. An outcome
-
by
-
outcome internal assessment
approach, which could lead to a compartmentalised view of psychology,
should be avoided.


GUIDANCE FOR TUTORS

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© Learni ng and Teachi ng Scot l and 2003

Guidance on app
roaches to assessment for this unit


The National Assessment Bank will provide assessment instruments and
guidance on implementation. This does not preclude teachers/lecturers from
devising their own assessment tasks. Evidence of attainment of the outcomes

for this unit may be provided through a variety of methods. However,
restricted
-
response questions are considered to be most appropriate. Where an
integrated approach is used for assessment, it will be necessary to identify in
the candidate’s response whe
re each outcome has been met.


Where assessment evidence is gathered by means of a single assessment
towards the end of the unit, care should be taken to ensure that sufficient time
is allowed for remediation and reassessment if required. Where a candidat
e
has failed to achieve one or more of the outcomes, it is only necessary to
reassess those outcomes that the candidate has failed to achieve.


Where assessments are set which allow candidates to demonstrate
performance beyond the minimum standard required
, evidence gathered for
internal unit assessment might also be used for grade prediction and for
appeals for external course assessment. For details of the grade descriptions
for external assessment, please refer to the Advanced Higher Psychology
course sp
ecification.



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OUTCOMES 1 AND 2: TH
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© Learni ng and Teachi ng Scot l and 2003

SECTION 2



Perception


The Scottish Qualifications Authority (SQA) ask that we consider, in relation
to the study of
perception
:




perceptual processing



theories and research of visual perception


constructivist, direct,
interactionist



computer models of visual perception



cultural, social and developmental aspects of perception.


By the end of this key concept you will have been introduced to the topic of
perception and should be able to understand it in terms of an information, or

mediational, process. The important area of visual perception will be
explained in terms of related theory and research. Computer models of how
psychology suggests we visually process information will be introduced,
along with discussion about cultural, s
ocial and developmental aspects of
perception.


Cognitive psychology concerns the study of our
cognitive
or
mediational
processes,
and is a discipline that

emphasises an internal explanation of our
behaviour. The word ‘cognitive’ comes from the Latin word

cognitio
meaning
‘apprehend, understand or know’. Cognitions, then, are those internal mental
processes that involve the mind (brain processes). Cognitive processes refer
to all the ways in which we obtain, use and process information from our
world in or
der to operate successfully within it.


Here we will first explore cognitive psychology generally in an attempt to
understand what cognition means. Secondly, we will look at two
key concepts

that enable us to gain and use knowledge of the world around us.
These key
concepts are taken from the whole range of cognitive processes that include
perception, memory, attention, language and thinking. All of these human
abilities or higher
-
level processes are inferred and cannot be observed
directly. This unit will
explore
two
of these different aspects of cognition as
key concepts, i.e.
perception

and
attention.


Study of other cognitive processes, and their applications, is at the discretion
of the tutor and candidates.

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But before we look at perception, we need
to know what is meant by
‘cognitive psychology’.



What is cognitive psychology?



Cognitive psychology involves the study of how we take in information
from
our world, and how we actively process this information to
respond
to
our world.


An information

processing approach


Cognitive psychologists study our higher
-
level cognitions of
perception: attention, language, memory and thinking (or
problem
-
solving). They believe the mind consists of these five
information processes, which we individually and co
llectively
use to operate in, upon, and through our environment. Consequently, the
cognitive approach explains human behaviour and mental process from the
point of view of
information processing
. Any dysfunction in our thoughts,
feelings and behaviours are

due to
faulty
information processing. What this
means is that we might have a problem with one or more of our five
mediational processes (identified above).


We
actively

process information


The cognitive approach is about how we
actively

process inform
ation using
our mediational processes, individually and collectively, to build up our
knowledge of the world. It asks how we make meaningful sense of stimuli in
our world, and our resulting behaviours in it.


The cognitive approach argues that we are no
t passive receptors of
information, as the behaviourist approach would have us believe. Our mind
actively processes what information it receives, and using mediational
processes, changes this information into new forms. New information is
combined, compar
ed, transformed and integrated with that which is already
present. On the basis of our information processes, we build up an
increasingly more complex picture of our world, and all the things in it,
which affects our feelings and behaviours in our environ
ment.


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© Learni ng and Teachi ng Scot l and 2003

The fall and rise of the cognitive approach


From its earliest beginnings psychology has tried to understand the human
mind in relation to feelings and behaviours. William Wundt is remembered
for his research in 1879 into perception. Freud is r
emembered for his work
(from 1901) concerning the unconscious. In
Perspectives

we discovered that
the behaviourist approach became popular largely because of its
criticisms
of
the study of such hypothetical constructs. As a consequence, the study of
what p
sychology originally understood itself to be


the study of the mind


became somewhat marginalised for a good part of the twentieth century. A
series of events was, however, to occur, aided ironically by a behaviourist,
which was to see the cognitive appr
oach overcome its difficulty of generating
scientific support for hypothetical constructs. This saw the rebirth of the
cognitive approach from about the 1970s onwards, helped in its renaissance
by developments in subjects as diverse as computer engineering

and cognitive
psychotherapy.


Tolman and Honzik (1930)


Behaviourism emphasises that psychology should study actual observable
behaviour, and that we are to be understood in terms of stimulus

response
units of behaviour learned via classical and operant
conditioning.


It was to be a ‘soft’ behaviourist, Edward Tolman, who challenged these
assumptions, when in 1930 he suggested that organisms
do
something with
learned S

R units that make them even more efficient and effective in their
environment. This wa
s to stimulate the important cognitive idea that we are
active

processors of information and not passive learners as behaviourism had
suggested.


In their famous experiment (1930) Tolman and Honzik built a maze
environment to investigate
latent learning
i
n rats.


Latent learning


Latent learning is a kind of subliminal learning, which we don’t know

we possess, and don’t use until there is some positive reinforcement,

or environmental incentive, to do so. An example of latent learning would

be where you
got a lift to college from a friend every day. You may learn

at a latent level the way to get to college, but as a passenger you have no
reason to demonstrate your learning by ‘proving’ that you know this.

You don’t even think about it. However, when yo
ur friend is sick and

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you have to drive yourself to college for the first time, if you follow the same
route as your friend did, then you have demonstrated latent learning.


Rats in mazes




















Plan of maze

14
-
Unit T
-
Alley Maze


Fig 1

(Fr
om M H Elliott, ‘The effect of change of reward on the maze

performance of rats’.
Univ. Calif. Publ. Psychol.
, 1928, 4, p. 20.)



In a variety of experiments with different kinds of mazes, Tolman found that,
when introduced to his maze, a rat initially sn
iffed about, and explored in an
erratic fashion. If it eventually discovered food placed in a food box, when it
was later put back into the maze the rat searched for the food and did not
make as many errors, i.e. go down blind alleys, turn back on itself,
etc.


as it
did when first introduced to the maze.


Cognitive maps


Tolman thought that what must have happened is that his rats had

formed a primitive
cognitive map
of the maze in their heads. The

cognitive map was formed as a result of their first ex
ploration of the

maze. Whether they used it to their advantage, as measured by going

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more quickly and with fewer errors to the food, depended upon this earlier
exploration of the maze, and whether they had been rewarded, or otherwise,
when coming acros
s the food box.



Purposive behaviourism


Tolman and Honzik concluded that cognitive maps allowed the rat to better
understand and react to its maze environment. The earlier behaviourists
seemed to be wrong in suggesting that organisms were
passive

learn
ers.
Tolman and Honzik (1930) indicated instead that rats are active processors of
information about their world. Further, organisms such as rats process what
they learn about their world in a very sophisticated fashion in order to obtain
some mastery over

it. This
purposive behaviourism

of non
-
humans, and by
behaviourist definition humans, was to stimulate developments in the
cognitive approach.


Behaviourism’s mechanistic and deterministic view, that we passively learn
in response to our environment, was

beginning to be questioned from within
behaviourism itself.


A conundrum solved


Tolman and Honzik had gone some way to help solve the conundrum that had
plagued cognitive research since Wundt in 1879. That is, how to investigate
and generate empirical
data about hypothetical constructs; which


remember!


don’t exist in reality, in order to come to a scientific
understanding of them. Tolman and Honzik
externalised

the construct of
thinking in rats and studied it
indirectly

by obtaining empirical data i
n terms
of times and errors made by the rats in the maze. Tolman and Honzik (1930)
were then able to confidently
infer

on the basis of this empirical evidence that
rats think in a more sophisticated fashion than earlier behaviourists had
believed. They had

the essential empirical data.



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© Learni ng and Teachi ng Scot l and 2003

Neural networks


The human equivalent of a cognitive map of our environment is
sometimes referred to as a
neural network
. Saaranin (1973) got
American college students to draw maps of their campus. Students
tended to enla
rge those buildings that were most important to them and
shrink the less important. They were often found to be completely
wrong when describing campus areas that were not as familiar to them.
Similarly, Briggs (1971) discovered, on asking people to judge
how far
they thought one landmark was from another, that they tended to
underestimate the distance between familiar landmark objects and
overestimate the distance between unfamiliar landmarks. This research
helps to explain the phenomenon of the Irish mile
!




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Interactive


Study

Tolman, E C and Honzik, C H,
Introduction and removal of reward and
maze
-
learning in rats
, University of California Publications in Psychology, 4,
257

275, 1930


Aim

To investigate latent learning in rats and the relationship betw
een
reinforcement, learning and performance.


Method

Experiment. Tolman and Honzik built a complex maze environment (see page
14). They had three groups of rats that underwent seventeen trials in the maze
over seventeen days under three conditions. Group
1 rats were never fed in
the maze, and when they reached the goal of the food box, were removed.
Group 2 rats received the reinforcer of food every time they reached the food
box, while on trials 1

10, Group 3 rats got no food but received
reinforcement on

trials 11

17.


Results

Group 1 rats always took around the same time to reach the food box and
made many errors. They were observed as aimless in the maze. They just
wandered around. Group 2 rats learned the intricacies of the maze quickly,
and over the
seventeen days of trials made progressively fewer and fewer
errors. From day 11 Group 3 rats showed a sudden improvement in
performance time to reach the food and made as few errors as Group 2 rats by
the end of the experiment.















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Conclusion

Tolman and Honzik (1930) concluded that reinforcement from the
environment may not be as important to the learning process as was
previously thought. They believed reinforcement was more related to the
performance

of a learned behaviour. Further, this expe
riment helped Tolman
infer that organisms such as rats and humans do something with learned units
of behaviour to make them more efficient in their environment. Tolman
(1946) was to say his rats had formed primitive cognitive maps of the maze
environment i
n their heads. Whether they used this information depended
upon a successful outcome to behaving in a particular way. We learn at a
latent level that may see us behave in a particular way if there is some
incentive from our environment for us to do so.



Interactive


1.

What do you think latent learning means? Give an example in
your answer.


2.

What was the relationship that behaviourism thought existed
between reinforcement and learning before Tolman and Honzik
(1930)?


3.

What are the three conditions

of the independent variable in
Tolman and Honzik (1930)? An independent variable is the
variable the experimenter manipulates or changes in an
experiment.


4.

What evidence did the experimenters find that reinforcement is
more related to performance of a

learned behaviour, rather than to
the learning of the behaviour itself?



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1956


a very good year


It is entirely good fortune that the author’s first birthday coincided with 1956
being the landmark year for the cognitive approach! For it would not be
i
nappropriate to say that 1956 precipitated the growth of cognitive
psychology, as it exists today.


This is because in 1956 the world famous psycholinguist Noam Chomsky
presented his paper on the theory of
language
, Jean Piaget and Bärbel
Inhelder wrote a
bout
egocentrism

in
The Child’s Conception of Space,

and
George Miller’s work on
short
-
term

memory

was published. In addition,
1956 saw Bruner, Goodnow and Austin debate
concept

formation
, or how we
develop different ways of thinking about the environment
around us. 1956
was also the year of the Dartmouth Conference in the USA, which saw the
beginnings of the AI (
artificial

intelligence
) movement energised by
innovations in computer technology.


Of importance here is that cognitive psychology gave the emer
ging computer
technologies their information processing models about how cognitive
psychology believed humankind thought and problem
-
solved. We share a
language, in that nowadays in cognitive psychology we often come across
words and concepts from informat
ion technology such as input, output,
storage, retrieval, parallel processing, networking, schema, filters, etc. This is
one reason why the approach uses the

computer analogy

to help explain why
it believes we think, feel and behave the way we do. This is
as an active
processor of information from our world, the outcome of which explains our
thoughts, feelings and behaviours.


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What is cognitive psychology? Interactive


1.

Noam Chomsky published a paper on the properties of language
entitled ‘Three model
s for the description of language’, in
I.R.E.
Transactions on information theory
, 1956.

Find out more at
http://www.rci.rutgers.edu/~cfs/305_html/Understanding/


LanguageProps.html


2.

Read Miller, G A, ‘The magical number seven, plus or minus two:
Some limits on our capacity for processing information’,
Psychological Review
, 63, pp. 81

97, 1956 at
http://www.well.com/user/smalin/miller.html



For a summary see
http://tip.psychology.org
/miller.html


3.

Read Piaget, J and Inhelder, B,
The Child’s Conception of Space
,
Routledge & Kegan Paul, 1956


4.

Investigate concept formation by Bruner, Goodnow and Austin
(1956) at
http://www.cse.unsw.edu.au/~billw/cs9414/notes/ml/01intro/


01intro.html




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The human mind, the cognitive approach and the computer


The cognitive approach and computer engineering
share the belief that the human mind/brain can be
likened to a compu
ter. What a computer tries to do
is mirror how the cognitive approach suggests we as
human beings problem
-
solve.


The computer analogy assists the cognitive approach to explain the
relationship between our information processes and our behaviour in our
wo
rld. Models like the computer analogy are used throughout psychology to
help us understand hypothetical constructs, and nowhere is their use more
prevalent than in the study of perception, attention, memory, etc. Models put
forward by cognitive psychologi
sts concerning our various cognitions have
greatly influenced developments in the computing industry. The more
advances that can be made in cognitive psychology the more likely it is that
the computer industry will be able to develop the ultimate in inform
ation
technology


an interactive free
-
thinking computer that can problem
-
solve
without direction. What the cognitive approach finds out is therefore of
great interest to the likes of Bill Gates and Microsoft
.


The computer analogy




Input

Processor

Ou
tput




S

X

R



Stimulus

Mediational

Response



processes


X = perception, attention, language, memory and thinking



In his book,
How The Mind Works

(1997), Steven Pinker wrote ‘the behaviour
of a computer comes from a complex interaction between the p
rocessor and
input’. This is very much how the cognitive approach understands
our
behaviour as human beings.


The computer analogy is a metaphor, or story, used by the cognitive approach
to understand the relationship between our thoughts, feelings, and b
ehaviours
and our environment.

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Input

means all the stimuli information that we encounter in our world.
Input, or environmental information, about objects, people, events, etc. comes
to us via our senses in the form of light energy, sound energy, pressure
, etc.,
or what we ‘see’, ‘hear’ and ‘feel’. All this information ultimately arrives in
the brain to be interpreted, understood and acted upon. A good example of
this would be the things we see in our world.


What we ‘see’, or visually sense, is energy f
rom our external environment
that first strikes each eye as light waves. This information, alien to our
internal biochemistry, is
processed

by special properties in our eyes into the
only type of energy our internal body can understand: electrical energy,
which ends up in the visual cortex at the back of the brain as a bundle of
electrochemical impulses, or neural signals. We unconsciously match the
degree and intensity of these neural signals to what we have stored in our
memory concerning the same, or a s
imilar stimulus. Memory helps us
recognise and give meaning to what we are visually sensing. This helps us
think how best to respond, in terms of our behaviour or
output
, towards the
stimulus object.


It is our information processes of perception, attenti
on, language, memory
and thinking (
X
) that come between the sensory information (
S
) we receive
from our world and our response (
R
) to it.
Information
processes therefore
intercede or come between external stimuli or input from our world, and our
behavioura
l response, or output, to it. Our information processes are like the
microprocessors in a computer. Microprocessors come between input in the
form of keystrokes, etc., and computer output like printouts and images.


The computer analogy helped to confirm
behaviourist Edward Tolman’s view
that we are more than just S

R units of learned behaviour. It also helps to
show that it is our mediational processes that actively do things with the
sensory information we receive, which allows us to respond to our world

in
an enriched fashion.


Let us now read about two information processes, perception and attention,
aware that the cognitive approach likens our mind to a computer


the most
sophisticated evolved.



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Perception


Introduction


In psychology we try fir
st to define the concept we are looking at.



Perception is...the process of assembling sensations into a usable mental
representation of the world...which...creates faces, melodies, works of art,
illusions, etc
.’

Coon (1983)



Perception is not determine
d by stimulus patterns, rather it is a dynamic
searching for the best interpretation of the available data...perception
involves going beyond the immediately given evidence of the senses
.’

Gregory (1966)


We should be careful however for:



To perceive see
ms effortless... to understand perception is nevertheless a
great challenge.


Dodwell (1995)


Here is an attempt at a definition:



Perception is the active cognitive
information process

by which we
take in raw sensations from our environment using our sen
ses, and
interpret these sensations using our past knowledge and understanding
of the world in order that the sensation, or what we are sensing,
becomes meaningful to us.




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Perceptual processing: how do we perceive?


An understanding of how we perceive
has intrigued cognitive psychologists
for decades. As will be discussed later, three explanations have emerged,
each enriching our knowledge of perception.


1.

The ecological view

(Gibson;
Gestalt



where we perceive in terms of
‘organised wholes’): where

it is said we perceive most clues from our
environment
directly

and without interpretation (we perceive ‘exactly’
what we see, hear, smell, touch and taste). The ecological view is
popularly known as bottom
-
up processing.


2.

The constructivist view

(Gr
egory; Bruner): where it is said our
perceptual system must often make a reality
indirectly

out of bits of
sensory information due to the absence of other information. The
constructivist view is better known as top
-
down processing. It is
perception by hypo
thesis testing.


3.

The interactionist

or
symbiotic (top
-
down/bottom
-
up) view
(Neisser): this says we use the most appropriate of the above two
processes depending on the situation we find ourselves in. The two
processing models work together. When one t
ype of perceptual process
(or aspect of it) is impaired, the other process (or an aspect of it) ‘fills
in’ or compensates to give us, at the end of the day, as much of an
understanding of the stimulus as possible. Interactionist processing is
best explaine
d in the area of visual perception using Marr’s Computer
Analogy, in which he says we first adopt a bottom
-
up approach to
extract visual information from an image/object/event in four stages and
put it all together again in the brain in what he calls a sym
bolic
representation of the stimulus. It is an explanation of visual perception
that sees our bottom
-
up and top
-
down processes working together.


Whether you advocate an ecological (direct bottom
-
up), constructivist
(indirect top
-
down) or interactionist/
symbiotic explanation of perception, it is
interesting to note the influence of the nature

nurture debate to your position.
While most of the theorists above suggest an empirical basis to our
perceptions (that what we perceive or ultimately understand from

what our
senses are telling us is the result of learning and experience), the influence of
Gestalt psychology in the early years of research into this topic does raise the
nativist position, that is, that our perceptual ability is innate, and needs little

if any ‘learning’ to enhance it.


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At the end of the day, we can say that perception is influenced by our innate
abilities as human beings, but also by the cognitive apparatus we are born
with as used to make meaningful sense of the myriad sensory experi
ences we
encounter. What we perceive, or understand, we are sensing is also strongly
influenced by what we have learned from past experience of the same, or
similar, sensations. Perception is further influenced by social, developmental
and cultural factors

including expectations and motivation.



Student Activity


1.

Define ‘perception’ in your own words.


2.

What aspects of being human processes are involved in
perception?


3.

What are the three views taken by psychologists as to how we
perceive our w
orld?


4.

Briefly explain these three views.


5.

Which at this stage in your studies do you think best explains
perception? Give reasons for your answer.



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Processing sensory information


Sensation and perception


In our original working definition, we

said that perception concerns sensing
plus our interpretation of this sensation based on meaningful past experience
of it. Central to perception must therefore be knowledge of how we receive
information from our environment in the first place. This is of
course through
our senses. We use our traditional five senses, i.e. sight, hearing, touch, taste,
smell, to receive information from our external world. Psychology is also able
to tell us we have at least one other sense that is called our
kinaesthetic

sen
se. This is a sense from within our own bodies that tells us about
movement, or the feel of our muscles or joints. Our kinaesthetic sense tells us
about balance


Our visual sense


Our sense of vision is in many respects our key sense. Vision, our visual
system and visual perception constitute the most studied information process
of all by cognitive psychologists; we look at it in more depth in a later
section en
titled ‘Our visual system’. Our sense of vision comes to us via our
eyes, the structure and location of which allow us to perceive our world in
three dimensions; sense colour; sense depth, etc.


Our tactile sense


Touch is another of our five senses, al
lowing for our
perception of pressure, touch, temperature (principally
temperature change), pain and hair movement. We
experience touch using sensory cells called receptors that
are nerve endings in the skin. Touch receptors are either
free ending (in the
dermis and around hair follicles) or
encapsulated (branched or coiled, enclosed in a capsule).
Receptors in our skin respond to a specific type of
stimulus and are not evenly distributed over the body. The
sensitivity of fingertips, for example, results fr
om a large number of touch
receptors we have at this extremity.


Once a receptor is stimulated, it sends nerve impulses to the brain, which
locates and identifies the stimulus involved and assesses its significance. The
more intense the stimulus, the grea
ter the frequency of nerve impulses.

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The skin’s sensory system is important in alerting the body to changes in its
external environment. Potentially harmful stimuli may cause pain that results
in either protective reflex actions, such as dropping a hot o
bject, or storing a
memory to remind you to avoid future similar hazards. The perception of pain
is unusual as it is also strongly affected by the emotions and the
circumstances in which it is experienced.


Our auditory sense


The ear is our organ of hear
ing and balance. It is
composed of three parts


external, middle and
internal


the greater part of which is enclosed
within the temporal bone. The external ear is that
portion of the hearing apparatus lateral to our
eardrum, or tympanic membrane. The ear
drum
comprises the auricle, or pinna (the external flap of the ear) and the external
auditory canal, which is 3 cm (1.25 in) in length.


The middle ear, on the inner side of the eardrum, houses our mechanism for
the conduction of sound waves to the interna
l ear. It is a narrow passage, or
cleft, that extends vertically for about 15 mm (0.6 in) and for about the same
distance horizontally. The middle ear is in direct communication with the
back of the nose and throat by way of the eustachian tube, which allo
ws for
passage of air into and out of the middle ear. Traversing, or going across, the
middle ear is a chain of three small, movable bones called the ossicles: the
malleus, or hammer handle; the incus, or anvil; and the stapes, or stirrup. The
ossicles con
nect the eardrum acoustically to the fluid
-
filled internal ear.


The internal ear, or labyrinth, is the part of the temporal bone containing the
organs of hearing and balance to which the filaments of the auditory nerve are
distributed. It is separated fro
m the middle ear by the fenestra ovalis, or oval
window. The internal ear consists of membranous canals housed in a dense
portion of the temporal bone and is divided into the cochlea (Greek for ‘snail
shell’), the vestibule and three semicircular canals. A
ll these canals
communicate with one another and are filled with a gelatinous fluid called
endolymph. The disposition and orientation of endolymph also helps us
experience our sense of balance.


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The ear and balance


The semicircular canals and the vesti
bule are concerned with our sense of
equilibrium, or balance. Hairs in these canals, similar to those that form the
organ of Corti (the structure responsible for converting sound signals into
nerve impulses), respond to changes in the position of the head.


The three semicircular canals extend from the vestibule approximately at
right angles to each other, providing sensory organs to record movements of
the head in each of the three planes of space: up and down, forwards and
backwards, and to the left or ri
ght. Lying over the hair cells in the vestibule
are crystals of calcium carbonate, known technically as otoliths and popularly
as ear sand. When the head is tilted, the otoliths shift, and the hairs beneath
respond to the change in pressure. The eyes and c
ertain sensory cells in the
skin and internal tissues also help to maintain equilibrium, but when the
labyrinth of the ear is damaged or destroyed, disturbances of equilibrium
invariably follow. With eyes closed, a person with a disease or disturbance of
t
he internal ear may be unable to stand without swaying or falling



How do we hear?


Sound waves, which are actually changes in air pressure, are carried through
the external auditory canal to the eardrum, causing it to vibrate. These
vibrations are communicated by the ossicular chain in the middle ear through
the oval

window to the fluid in the inner ear. The movement of the
endolymph stimulates the movement of a set of fine hair
-
like projections
called hair cells as the cochlea vibrates. Collectively these projections are
called the organ of Corti. The hair cells tran
smit signals directly to the
auditory nerve, which carries information to the brain. The overall pattern of
response of the hair cells to vibrations of the cochlea encodes information
about sound in a way that is interpretable by the brain’s auditory centr
es.


The range of hearing, like that of vision, varies from person to person. The
maximum range of human hearing includes sound frequencies from about 16
Hz to 28,000 Hz. The frequency at which we can detect sound is measured in
Hertz (Hz), or cycles per s
econd. The least noticeable change in tone that can
be picked up by the ear varies with pitch and loudness. A change of vibration
frequency (pitch) corresponding to about 0.03% of the original frequency can
be detected by the most sensitive human ears in
the range between 500 and
8,000 vibrations per second. The ear is less sensitive to frequency changes for
sounds of low frequency or low intensity.

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The sensitivity of the ear to sound intensity (loudness) also varies with
frequency. Sensitivity to change
in loudness is greatest between 1,000 and
3,000 cycles, where a change of one decibel can be detected


and becomes
less when sound
-
intensity levels are lowered.


The variation in the sensitivity of the ear to loud sounds causes several
important phenomena
. Extremely loud tones produce in the ear entirely
different tones that are not present in the original tone. These subjective tones
are probably caused by imperfections in the natural function of the middle
ear. The harshness in tonality caused by greatly

increasing sound intensities,
as when a radio volume control is adjusted to produce excessively loud
sounds, results from subjective tones produced in the ear. The loudness of a
pure tone also affects its pitch. High tones may increase as much as a whole
musical
-
scale note; low tones tend to become lower as sound intensity
increases. This effect is noticeable only for pure tones. Because most musical
tones are complex, hearing is usually not affected to an appreciable degree by
this phenomenon. In sound ma
sking, the production in the ear of harmonics of
lower
-
pitched sounds may deafen the ear to the perception of higher
-
pitched
sounds. Such considerations make it necessary to raise one’s voice in order to
be heard in a noisy place.


Our gustatory sense


T
aste is another of the five senses, effected by the
contact of soluble substances on our tongue
Although humans can distinguish a wide range of
flavours, the sensation of taste is actually a
response to a combination of several stimuli,
including texture,
temperature and smell, as well
as taste. In isolation, the sense of taste can only
identify four basic flavours: sweet, salt, sour and bitter, with individual taste
buds particularly responsive to one of these. The 10,000 or so taste buds
found in humans a
re distributed unevenly over the top of the tongue, creating
patches sensitive to specific classes of chemicals which give the taste
sensations. Usually sweet and salt are at the tip of the tongue, sour at the
edges, and bitter at the base. Chemicals from
food are dissolved in the
moisture of the mouth and enter the taste buds through pores in the surface of
the tongue where they come into contact with sensory cells. When a receptor
is stimulated by one of the dissolved substances, it sends nerve impulses t
o
the brain. The frequency of the repetition of the impulse tells the brain how
strong a flavour is and the type of flavour is probably registered by the nerve
cells that responded.


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Our olfactory sense


Smell is the sense by which odours are perceived
. The
nose, equipped with olfactory nerves, is the special
organ of smell. The olfactory nerves also account for
differing tastes of substances taken into the mouth, in
that most sensations that appear introspectively to us as
tastes are in essence really
smells! Sensations of smell are difficult to
describe and classify, but noting the chemical elements of odorous substances
has made useful categorisations. Research has pointed to the existence of
seven primary odours


camphor
-
like, musky, floral, pepperm
int
-
like,
ethereal (dry
-
cleaning fluid, for example), pungent (vinegar
-
like) and putrid


corresponding to the seven types of smell receptors found in the olfactory
-
cell hairs. Olfactory research also indicates that substances with similar
odours have mole
cules of similar shape. Recent studies suggest that the shape
of an odour
-
causing chemical molecule determines the nature of the odour of
that molecule or substance. These molecules are believed to combine with
specific cells in the nose or with chemicals
within those cells. This process is
the first step in a complex series that continues with the transmission of
impulses by the olfactory nerve and ends with the perception of odour by the
brain.


How do taste and smell work?


Taste and smell are a part of
our sensing system much like vision and
hearing. Molecules released by substances around us stimulate special nerve
cells in the nose, mouth or throat. These special nerve cells transmit electric
impulses to special areas of the brain that recognise taste
and smell. Olfactory
nerve cells are stimulated by odours around us such as flowers, baked goods,
perfumes, etc. These olfactory nerve cells are located in a tiny patch high up
in the nose. They connect by nerve pathways to areas in the brain.


Taste cells

react to food and drink, mixed with saliva, and are located in the
taste buds of the mouth and throat. Many bumps on the back of the tongue
contain taste buds. These taste cells send information along nerve pathways
to the brain. Unlike other nerve cells,

taste and smell cells are replaced when
they become old and damaged.


Another set of cells in the nose and mouth have non
-
specialised nerve
endings that are stimulated by strong and irritating sensations such as
ammonia, chilli peppers, onions, etc.

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As
already stated, we can commonly identify four basic taste sensations:
sweet, sour, bitter, salt. And there is some evidence that other taste sensations
can be appreciated. But the sense of smell is necessary to identify flavours
such as chocolate; the swee
tness is identified by the nerve cells of the tongue
and mouth. The combination of saliva with the chocolate releases odours and
molecules. These travel up the nasal passage from the back of the throat. The
nasal cells are stimulated and the smell and flav
our of chocolate are
recognised. This is why people who complain of taste problems really often
have a smell disorder that interferes with the ability to identify the flavour of
foods.


Our internal and external senses interact with each other because we
are
constantly linking together information got through differing
sensory modes
,
e.g. seeing, hearing, etc. This involves us in what is called
cross
-
modal
transfer



where information gained using one mode, e.g. sight, is applied to
information from anothe
r sensory mode, e.g. hearing. Cross
-
modal transfer
gives rise to a richer array of sensory information upon which we base our
interpretation of our own realities (world)


but by that we often become
confused.


Characteristics of our sensory system


Our s
ix modalities (or senses) have certain common characteristics. Before
looking at what these are, please list below both the common and scientific
name for each:



Apparatus

Sense


1.

Eye

Visual

2.



3.



4.



5.



6.




Each responds to a parti
cular form of energy or external information,

e.g. light waves, sound waves, skin pressure, etc. Each has a sense

organ or ‘accessory structure’, which is the first port of call for any

incoming information on the road to processing, and full understan
ding of

the perceived stimuli. Each accessory structure has sense receptors called
‘transducers’. These are specialised cells that are sensitive to particular

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kinds of energy. It is as the stimuli impinge on these transducers that the
conversion of the

stimuli into electrical nerve impulses occurs. This electrical
activity is the only kind of energy that can be processed and understood by
our brains.


Each sensory modality involves a different part of the brain. We are here able
to interpret messages re
ceived from our sensory receptors, which gives us the
experience of conscious awareness of an object, a person, a word, a sound, a
taste, etc. A certain minimum stimulation of a sense receptor is needed before
we can become consciously aware of the sensory

experience that is
happening. These minimum requirements are called absolute thresholds,
which are based on a value given to a stimulus when we can detect it 50% of
the time. The threshold at which we can notice a stimulus differs among and
between people
, and can be affected by an individual’s physical state; time of
day; motivation; the way the stimulus is presented, etc.


This is the area of
psychophysics

within psychology (the interface between
the physical stimulus and our subjective experience of it
), which is of great
importance to the development of psychology as a subject in its own right
(see Wilhelm Wundt, 1879).



Student Activity


1.

What do you understand by our visual sense; our tactile sense; our
gustatory sense; our auditory sense; and ou
r olfactory sense?


2.

Describe and explain our kinaesthetic sense.


3.

How do we first begin to interpret information coming to us from
our environment? What is particularly interesting about this from
the point of view of psychophysics?


4.

What does
cross
-
modal transfer mean? Why is cross
-
modal
transfer important?


5.

What do you understand by the term ‘absolute threshold’? Give
three examples from your reading. Cite your sources using the
Harvard Referencing System.




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Our visual system


Vision and

visual perception is by far the largest area of investigation
undertaken by cognitive psychologists. A full understanding needs a little
introduction to the eye. The eye, according to Ornstein (1975) is ‘
the most
important avenue of personal consciousness
’. We receive around 80% of our
information about our world via our visual system.


Our visual sense


As already noted, sight or our sense of vision is probably the most studied of
all our senses thanks to the vast amount of work which has been done in the

area of visual perception.


A basic understanding of the structure and function of the eye is therefore of
relevance


if only to give us a clue as to how and why we receive 2
-
D type
photographic images on our retinas but interpret these two dimensional
images in three dimensions. A knowledge of our visual system is also
important to our understanding of how and why it is we can perceive colour
and depth in our world


and why it is we can see in the dark, but not as well
as cats and other nocturnal anima
ls!


Structure and function of the human eye


The
pupil

is the wee black circle at the
centre of each of our eyes. The pupil
controls the amount of light taken in by
the eye. In dark conditions our pupil
dilates to its maximum size in order to
maximise th
e amount of light entering
the eye and thus our ability to see (not
too well) in the dark. In light conditions
the pupil constricts, or ‘shrinks’, in
response to the intensity of light we experience. Pupil size is controlled by
our autonomic nervous system

(ANS) which controls organs and glands. The
ANS is linked to our central nervous system (CNS), our brain and spine.
Interestingly the ANS has two branches:




the
parasympathetic branch
, which in this instance changes pupil size in
response to illuminatio
n, and,



the
sympathetic branch

which in this instance dilates the pupil under
conditions of strong emotional arousal.


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The two branches of the ANS are self
-
regulating rather than under our
conscious control. Regulatory control of the ANS is directed by

the
hypothalamus, found in the brain. Both branches of the ANS are what
psychologists call
antagonistic

to one another. As one branch moves us to
action in one direction, the other counters this.


Vitreous humour
is the clear, jelly
-
like substance that f
ills the middle of the
eye. Dilation of the pupil is controlled by the
ciliary muscles

found in the
iris. The
lens

of the eye is held in place by suspensory ligaments. Much like
a camera, the lens focuses light on the retina as an inverted or upside
-
down
image. Ciliary muscles control the shape the lens forms as it focuses light
energy on the retina.


The lens thickens and increases in curvature when focusing on nearby objects
and becomes flatter when we are focusing on objects far away. Muscles
around the

eye adjust the shape of the lens to focus on an object either nearby
or far away. The lens gets thicker when focusing for near objects, and thinner
for distant objects. The size of the image reflected on the retina also changes.


The
retina
, which is foun
d at the back of the eye, is where images we see are
thrown. The
macula
, which is a small area found on the retina, has three
layers of specialised light
-
sensitive cells. Each of the layers helps explain
certain human visual abilities, and consequently per
ception.



The three layers of the retina


The first layer of the retina contains what are called
rods and cones
.


Rods and cones are photosensitive transducer cells that convert
light energy into electrical nerve impulses. Our
120M rods

help
us see in

ever decreasing light.


Our
7M cones

allow us to experience
chromatic

vision

(colour). Different cone types respond to the three primary
colours of red, green and blue. This is because each of these
colours has different wavelengths. Mixtures of red, gree
n and
blue allow us to experience all the colours found in the colour
spectrum. A deficiency in one or more of these cone types is the reason for
colour blindness.


Bipolar cells
, a second layer in the retina, are connected to our rods and
cones and help
relay information to ganglion cells found at the third layer of
the retina.

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Finally, in the retina we find a third layer called
ganglion cells
. Ganglion cell
fibres (
axons
) help form the beginnings of the
optic nerve
.


Three types of ganglion cell ‘fire’

in response to the contours and movement
of objects in our visual array or field of vision


simple cells

have been found
to respond to simple features of a stimulus, i.e. straight lines, edges, slits,
etc., when found in a particular orientation, or way
-
up, in our visual field.
Complex cells,

which are direction sensitive, have been found to respond to
lines of particular orientation wherever found in our visual field, and

hypercomplex cells

deal with the length of visual stimuli, or where a
stimulus begi
ns and ends.


The visual pathway


The visual pathway from each eye to the visual cortex in our brain is called
the
optic nerve
. Each optic nerve converges and crosses over at the
optic
chiasm

or chiasma, thus information from our right eye goes to the lef
t visual
cortex and information from our left eye goes to the right visual cortex.















Let’s take a journey along the visual pathway. Light rays from sources either
artificial or natural are reflected off distant objects in our surroundings.
These light rays first enter into the eye by passing through a clear tissue
called the cornea. From the cornea, light then passes through a clear fluid
termed the aqueous humour and then through the pupil opening of the iris in
order to reach the crystall
ine lens.


Using its two muscle bands in bright situations, the iris constricts to

protect the retina from too much damaging light, while during dim light
situations, the iris dilates to let in as much light as possible. The pupil,

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which appears as a

black dot in the middle of the coloured iris, is actually not
a structure but an aperture, a controlled opening or hole! Through the pupil,
light reaches the crystalline lens. The lens


in conjunction with the cornea


acts to bend or ‘refract’ the lig
ht in order to focus the rays on to the retina.
From its name you might believe the crystalline lens does most of the
refracting of the eye but this is not the case. It is the cornea that is the
primary refractive surface of the eye. Eighty
-
five percen
t of the job of
bending light is performed by the cornea, while the remaining fifteen percent
is done by the lens. The crystalline lens does have one advantage over the
cornea. The power of the cornea to bend light is fixed, whereas the
crystalline lens

can flex to provide more power in order to see near objects.
The lens is held in place behind the pupil by hundreds of fibrils termed
zonules. When we focus on near objects, these fibres relax allowing the lens
to curve outward, thus increasing its pow
er to refract light. When looking at
distant objects, the zonules pull tight and the lens flattens. The process of
lens flexure in order to see near objects is termed accommodation (which
should not to be confused with Jean Piaget’s notion of accommodati
on of
schema). From the crystalline lens, light rays travel through another clear
medium termed the vitreous humour until it reaches the retina.


When light enters through this whole optical system, it is actually inverted by
the process. An image in the
outside world is actually upside
-
down and
backwards when reaching the retina. It is the brain that later processes the
image the correct way. The retina is the central mechanism for collecting
light rays and converting light energy into electrical impuls
es that the brain
can ultimately understand. The retina contains millions of nerve cells with
photoreceptors attached to each one. There are two major photoreceptors
located in the retina. Rods are long, slender receptors that occupy the
peripheral reti
na. Rods are responsible for detection of movements, detection
of shapes and night
-
time vision. Our fine detail and colour vision is provided
by the cone receptors. These cone
-
shaped cells occupy only a small portion
of the retina and are found huddled

together in what is called the macula.
The portion of vision responsible for the most detail actually takes up the
least amount of room on the retina. Cones are divided into three subtypes


red, blue and green.


When light hits these red, green and blue

photoreceptors, a light
-
activated
chemical reaction occurs within the cells converting a photon of light

into an electro
-
chemical impulse. Visible light is a spectrum like that

of a rainbow. Each colour of the rainbow has a particular frequency in

t
hat spectrum. The complex process of colour vision occurs when

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light of a particular frequency stimulates either the red, blue or green cone
that is most sensitive to that given frequency. The quantity of
photoreceptors, as well as the type of receptor
s stimulated, is later interpreted
by the brain as a stimulus intensity and colour. From stimulation, light
energy is transformed into an electric current for the body. This current then
flows along each individual nerve until it reaches the optic nerve
of the eye.
The optic nerve is termed a nerve but it is actually a collection of about a
million nerves rolled into one.


We have two optic nerves: one for each eye. The optic nerve extends from
the back of each eye. They then enter into the skull thro
ugh a small opening
in the back of the bony orbit that protects the eye. From here the optic nerves
travel a short distance before they meet up with each other at a structure
known as the optic chiasma/chiasm. At the optic chiasma, some of the nerve
fibre
s from the right optic nerve cross over to the left side and vice versa.
This crossing of optic nerve fibres causes everything we see off to the right in
each eye to be processed by the left brain and everything off to the left in our
surroundings to be p
rocessed by the right brain. After parts of each optic
nerve cross at the chiasma, they continue on into what is called the optic
tract. This is where the optic nerves travel around the brainstem, one nerve
to the right hemisphere and the other to the le
ft hemisphere of the brain.
From here everything mentioned occurs on both the right and left sides of the
brain. The optic tract carries impulses to another processing area in the brain
called the lateral geniculate nucleus (LGN). This structure is like
a switching
station. Before the impulses even reach the LGN, a small amount of fibres
from the optic tract split off to other areas of the brain that control dilation
and constriction of the pupils. After the LGN, each nerve ‘fans’ out into
what is calle
d the optic radiations. Some of the nerve travels over the parietal
lobe of the brain while others travel the low road over the temporal lobe. The
nerves continue on until they reach the back portion of the brain called the
occipital lobe. At the occipit
al lobes all the impulses from the right and left
eyes are processed into what we perceive as our visual reality. The
information between the two eyes is also compared to create our three
-
dimensional world.


Discussion point


What do you understand by
the term ‘sensation’? How does a sensation differ
from a perception, properly known as a percept?


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Where all sensory information ends up to be processed and understood


This is of course in our brain, the organ concerned with consciousness.
Consciousness
is our awareness (plus perception; attention; language;
thinking and memory) and the overall control of the body. The human brain is
a relatively small structure, weighing about 1.4 kg (3.1 lb) and making up
about 2% of total body weight. It is contained w
ithin the skull, which acts as
a protective casing. Although the brain is only a small proportion of overall
body weight, information received about the outside world and from the rest
of the body converges at the brain to be processed. Sensations arrive h
ere and
are processed. We first begin to perceive what a particular sensation is (and
therefore what it is we are experiencing) on the basis of how good, bad or
indifferent our various senses are individually and collectively. How we reach
individual under
standing of what particular sensations mean for us is further
based on some innate abilities, plus any previous experiences we have had in
connection with them.


Processing sensory information



Cortical area

Function

Prefrontal Cortex

Problem
-
solving,

emotion, complex
thought

Motor Association Cortex

Co
-
ordination of complex movement

Primary Motor Cortex

Initiation of voluntary movement

Primary Somatosensory Cortex

Receives tactile information from the body

Sensory Association Area

Processing of m
ultisensory information

Visual Association Area

Complex processing of visual information

Visual Cortex

Detection of simple visual stimuli

Wernicke’s Area

ianguage comprehension

Auditory Association Area

Complex processing of auditory
information

Audit
ory Cortex

aetection of sound quality EloudnessI toneF

Speech Centre (Broca’s Area)

ppeech production and articulation



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Conclusion: sensation and perception


What we see is more than just light focusing on the retina of the eye. Vision
is an enormous
ly complex process. That which is seen must be captured by
the optical system, transmitted and processed by the retina, and then passed
along to the brain for even more detailed processing. Areas of the brain must
extract and interpret the essence of all
that we see. It must recognise colour,
contour, shape, texture, movement and perspective, then compare all this
information to our ‘internal database’ (or meaningful similar or same
previous experiences). A tiny, two
-
dimensional image hitting the retina m
ust
be transformed into a three
-
dimensional world all


pardon the expression


in the blink of an eye!


Vision is defined by two components: sensation and perception. The
concepts of sensation and perception are difficult to separate but
sensation

is
th
e detection and encoding of visual stimuli, whereas
perception

is the
higher
-
level cognitive process that processes, organises and interpretes this
visual sensation.


Perception should thus be seen as an active cognitive process influenced by
our intern
al and external world. These aspects of perception will now be
addressed.



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Student Activity Interactive


First experiment


Steadily fixate on the black light bulb for thirty
seconds or more. Try not to avert your gaze. Then
immediately turn your gaz
e to the white region on the
right next to the bulb (or a blank white sheet of paper).
You should see a glowing light bulb!


So what’s going on?


The glowing white light bulb you see on the white background after
staring at the black light bulb figure is c
alled an
after
-
image
. When
you focus on the black light bulb, light sensitive photoreceptors (whose
job is to convert light into electrical activity) in your retina respond to
the incoming light. Other neurons that receive input from these
photoreceptors
respond as well. As you continue to stare at the black
light bulb your photoreceptors become desensitised (or fatigued).


Your photo pigment is ‘bleached’ by this constant stimulation. The
desensitisation is strongest for cells viewing the brightest part o
f the
figure, but weaker for cells viewing the darkest part of the figure. Then,
when the screen becomes white, the least depleted cells respond more
strongly than their neighbours, producing the brightest part of the after
-
image: the glowing light bulb. T
his is a negative after
-
image, in which
bright areas of the figure turn dark and vice versa. Positive after
-
images
also exist. Most after
-
images last only a few seconds to a minute
because, in the absence of strong stimulation, most nerve cells quickly
re
adjust. Desensitisation of the retina can be important for survival. A
constant stimulus is usually ignored by the brain in favour of a
changing one, because a changing stimulus is usually more important.
But desensitisation also leads to after
-
images.


After
-
images are constantly with us. When we view a bright flash of
light, briefly look at the sun, or are blinded by the headlights of an
approaching car at night, we see both positive and negative after
-
images.


To prevent permanent damage to your eyes,

never

look at any

bright light source, in particular the sun. The British psychologist
Kenneth Craik burned a tiny hole in his right retina and



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permanently scarred his eye at that spot, when he stared directly into
the sun for two minutes. Don’t try

this at home! For the first few days
following his experiment


in which he wanted to find out whether such
a lesion in the eye is visible


he saw a dim orange disk with closed
eyes (positive after
-
image) and a black after
-
image with open eyes.
Fortun
ately, after a year or so, Craik’s vision at that location in his eye
appeared to return to normal. His brain cleverly filled in information at
this damaged piece of his retina.


Second experiment

Notice that if the after
-
image is viewed on the screen o
r on a nearby
sheet of white paper, it appears relatively small. If it is viewed on a
distant wall, however, it appears much larger, even though the size and
shape of the retinal image remains the same. The perceived size of the
after
-
image varies directl
y with the distance of the surface on which it
is viewed. This relation is an instance of a more general perceptual
relation known as Emmert’s law:
The perceived size of a particular
visual angle is directly proportional to its perceived distance
.


The il
lusion of after
-
images appearing to vary in size despite a constant