On 18 September, 2004 the Health Practitioners' Competency Assurance Act HPCA came into force.

1
On 18 September, 2004 the Health Practitioners'
Competency Assurance Act (HPCA) came into force.
The Act deems all psychologists to be health
practitioners. Under the Act, section 7(1)
states "A person may only use names, words,
titles, initials abbreviations or descriptors
stating or implying that the person is a health
practitioner of a particular kind if the person
is registered ... as a health practitioner of
that kind." The penalty for breach of this
provision is a fine of up to 10,000. From the
18th September, the law protects the titles
Psychologist, Clinical Psychologist,
Educational Psychologist, and Trainee
Psychologist. Only those registered by the
Psychologists' Board within one of the recognised
scopes of practice will be legally permitted to
use any of these terms as a title or description
of themselves or their work. This means that
academic staff who are not registered may not use
the title or descriptor "Psychologist". It is
still legal for non-registered staff to use the
title "Lecturer in Psychology" or Professor of
Psychology" etc.
2
Animations in P\My Documents\PSYC104 PPT
Lectures\AVI

• PSYC103/PSYC104 2004
• Perception Part 1

Murray Simmonds Psychologue Psychologe Psicólogo P
sycholoog Psicologo
(In English Non-Psychologist).
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• Where the term Psychologist appears in this
  Powerpoint presentation, please read
• Non-psychologist.

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Constructivist Definition of Perception . .
. the process by which we recognise what is
represented by the information provided by our
sense organs. (This is a fairly cognitive
definition). Perception is a rapid, automatic,
unconscious process it is not a deliberate one
in which we puzzle out the meaning of what we
see.
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The notion of REPRESENTATION. What is the main
aim of Psychology? ( e.g. in science
fiction?) Is it to account for behaviour? Or is
it to account for the contents of
consciousness? Party conversation Oh so you
are a psychologist . . . . . .Does that mean you
can read my mind?
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• Can visual perception can be defined in terms of
• what is on the retina?
• How much of what is on the retina is represented
• in conscious awareness at any point in time?
• Is attention narrowly focussed?
• How much can you see out of the corners of
• your eyes while gazing straight ahead?

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Machs sketch of the world as seen from his left
eye.
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• Many experiments show how information on the
• retina often retina gets missed by the
  perceiver.
• Research on attention
• Change Blindness
• Blindsight.

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Change Blindness When one picture
rapidly follows another with a blank screen in
between, people are remarkably poor at noticing
what is different about the two pictures.
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So we do not always perceive what is given on
the retina. The opposite is also true We
sometimes perceive things that are not on the
retina e.g. the filling in of the blind
spot.
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How a uniform array of elements is
perceived (when viewed with one eye)
What is actually on the retina if one of the
elements falls on the blind spot
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In terms of what is on the retina at any point in
time, there is always a missing portion of the
visual field in the area covered by the blind
spot of each retina.
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Complex processes operate to fill in the blind
spot. Left-eye view
Right-eye view
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With both eyes open the missing information is
easily filled in from what is available in the
other eye. The point is that even with one eye
closed, the blind spot in the open eye still
gets filled in.
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Blindsight DB had intense headaches from about
age 14. Eventually surgeons removed a large chunk
of his visual cortex to relieve the headaches but
this left him blind across almost his entire
left visual field. When shown small projected
lights on the left side of a screen he reported
seeing nothing. But when asked to point to the
position of the lights he was almost as accurate
with lights in the left field as with lights in
his undamaged right field.
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He had no conscious REPRESENTATION of the light,
yet his ACTION of pointing to it showed almost
no inaccuracies. Apparently some visual
information was being accurately processed at
lower levels in his visual system, but he was
completely unaware of the fact!
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• The Take-home message
• We cannot account for perception merely by
• describing the retinal image.
• Nor can we fully account for perception in
• terms of what is represented in conscious
• awareness.

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• GESTALT PSYCHOLOGY
• An approach to perception that began
• in Germany around 1910.
• It explored the ways in which the perception of
  
• objects could be understood in terms of simpler
• building blocks.
• It is still useful in object perception and in
  the
• psychology of music and the arts.

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The Gestalt psychology movement began by asking
a fundamental question in perception What is
the minimal stimulus configuration required for
perceiving MOTION?
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The Phi phenomenon (Apparent Movement
Demonstration) . . . originally used two
lights in a dark room.
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Gestalt psychology is best remembered for the
statement The whole is different from the
sum of its parts
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The previous slide was a magnified view of
the right eye of this face.
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Sometimes new properties emerge when a
configuration is perceived as a whole
The whole is different from the sum of its parts
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What are the initial building blocks of
perception from which form or object perception
proceeds? Gestalt psychology explored the
problem of ELEMENTS of perception and
their GROUPING with rather simple arrays of
elements
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Although they used only simple demonstrations
of grouping, the principles they uncovered may be
applied to more complex configurations of
points of stimulation
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Gestalt Psychology and SUBJECTIVE CONTOURS
Here perceiving the whole leads the brain to
construct something that isnt present in the
retinal image.
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Sometimes additional retinal information is
required for us to perceive the whole.
(Context effects).
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Perception often involves GOING BEYOND THE
INFORMATION GIVEN.
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The Phi phenomenon again
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What if we add a wall between the two positions
of the moving ball? (the position of the ball
has NOT been changed)
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Different CONCEPTUAL possibilities (going beyond
the information given) The ball goes around the
end of the wall. . . . . or . . . It goes
under/over/through the wall. Top views of the
model used to animate the demonstration
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A longer and higher wall (the position of the
ball has not been changed)
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What we perceive is sometimes logically
incompatible with what we know PERCEPTION vs
CONCEPTION e.g. I couldnt believe my eyes . .
. In many illusions we know that what we are
seeing is not really true. But what we know
doesnt stop us from seeing the illusion.
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Some other illusions Even if you KNOW the
following two illusions contain straight,
parallel lines (e.g. by measuring them up with a
ruler) that will not stop you from seeing the
illusion of bent lines.
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Perception is not always entirely determined
by the stimulation that we are currently exposed
to. Past experience sometimes plays a part in
determining what we perceive at any given
moment. Recent past events can also play a part
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Thus, perception can change over time in
response to unchanging stimulation. (e.g. the
spiral after-effect).
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The assumptions we make about the environment
can influence what we see. Perception may thus
be regarded as a CONSTRUCTIVE ACT. We construct
our perception of the world - a combination of
what is currently being received by the senses
and what we have perceived in the past. - i.e.
past experience plays a part in perception. That
is, what we know, or what we assume can
sometimes influence what we perceive.
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Assumption Surfaces often hide other surfaces
beneath them
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Here we make (changing) assumptions about what is
figure and what is background.
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Here is a three-dimensional model of the
impossible colonnade. It can only be viewed from
one fixed position in space.
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Based on past experience, we make assumptions
about the shape of a face
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• If we are given just a few points, we fill in the
  missing information to perceive a rigid object in
  depth

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Johanssons demonstrations of biological motion
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Quite specific information can be read out of
point-light displays (e.g. Distinctive gaits,
gender differences).
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History of modern Constructivism Helmholtz
(1867)Shape constancy (recognizing a table from
different viewpoints).
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Helmholtz, H. (1867) Treatise on physiological
Optics . . .perception depends upon a
process of unconscious inference . . . . . .we
use hidden assumptions, in conjunction with
retinal images to reach perceptual conclusions
about the environment.
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Gregory (another modern constructivist) Perceptio
n is a HYPOTHESIS about what is out there in the
real world.
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How many human faces in this Bev Doolittle
picture?
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Reversible figures
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Impossible figures
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Trompe loeil art
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Sala Della Prospettiva in Farnese Palace, Rome
with partly painted view over Ancient Rome.
(Renaissance Virtual Reality?)