Transcript Visual Perception - PsychAtRuthven2010

VISUAL PERCEPTION
Area of Study 2
Visual Sensation
Visual Perception
-Physiological
- Visual sensation is the same
for everyone
-It is our physiological make up
of the eye and the way it
functions
- Psychological and
physiological
-Visual perception differs as
everyone perceives and
interprets things differently
-When studying Visual
Perception it is difficult to say
where one starts and the other
begins so we see it as an
interrelated process.
-Reception
-Transduction
-Transmission
-Selection (also occurs in
sensation through reception
process)
-Organisation
-Interpretation
Absolute Threshold
Differential Threshold
- is the minimum amount of
energy needed to detect a
stimulus under ideal conditions
fifty percent of the time.
-is the smallest difference in the
amount of a given stimulus that
a specific, sense can detect.
- For example, the absolute
threshold for the visual sensory
system enables us to see a candle
flame at 50 kilometres .
-For example, the differential
threshold enables us to perceive
difference in two separate
stimuli (i.e. When we go to an
optometrist). When a change can
no longer be detected it has
exceeded our threshold.
Process
Description
Reception
Reception or capture of visual stimuli in the
retinas of the eye by sensory neurons called
photoreceptors.
Transduction or conversion of electromagnetic
energy (light energy) into electrochemical
energy (or neural impulses) by photoreceptors
Transduction
Transmission
Transmission of neural impulses, via one neuron
to another, through the optic nerve to the
brain.
Selection
Selection of features of a stimulus by
specialised neurons in the visual cortex called
feature detectors.
Organisation
Organisation of the stimulus features into
patterns or groupings to closely represent the
original stimulus in a meaningful way.
Interpretation
Interpretation or understanding of what the
stimulus represents in the external world.
Sue Requires Two Things,
whereas Paul Selects One Item.
Sensation involves Reception, Transduction and
Transmission,
While Perception involves Selection, Organisation and
Interpretation of information.
Monocular Depth Cues
Binocular Depth Cues
Accommodation (A)
Retinal Disparity (R)
PICTORIAL CUES:
Convergence (C)
Texture Gradient (T)
Height in the visual field (H)
Relative Size (R)
Interposition (I)
Linear Perspective (L)
CAR THRIL
Gestalt Principles
Constancies
Figure-Ground
Size Constancy
Closure
Shape Constancy
Similarity
Orientation Constancy
Proximity
Brightness Constancy
Visual Illusion
Explanation
Muller-Lyer
Perceptual compromise Hypothesis (Ross Day)
- Two or more visual cues conflict with each
other when interpreting visual information.
Ames-Room
Apparent distance hypothesis
-When two retinal images are the same size, but
one that appears to be a greater distance then
the one that appears to be further will be
interpreted as larger.
-Size constancy fails
PERCEPTUAL SET (EXPECTANCY):
Perceptual set is a predisposition or expectancy to perceive stimuli in a
specific way.
Context
Past Experience
-Context refers to the setting in
which a perceived stimulus
occurs.
-Past experience can affect
visual perception, especially if
the experience holds significant
personal meaning.
- In other words, context refers
to the physical or circumstantial
surrounds in which the observed
event or object sits.
-The subjectivity of the
experiences may cause particular
stimuli to be interpreted
differently by different people.
Figure-Ground
Closure
Proximity
Closure
Closure
Similarity
Figure-Ground
Convergence
Accommodation
Retinal Disparity
Relative Size
Texture
Gradient
Height in the
Visual Field
Interposition
Linear Perspective
Orientation
Constancy
Size
Constancy
Brightness
Constancy
Shape
Constancy
Which of the following structures is first to be involved in the process of
selection in visual perception?
a) The photo receptor cells
b) The lens
c) The neurons in the visual cortex
d) The optic nerve
Anna has chronic sinusitis (blockage of the canals that drain into the nostrils)
and headaches. Her plastic surgeon decided that instead of drilling a hole
in the bridge of her nose, her will push a tube down the corner of her eye
through the ciliary muscles and clear the nasal passages. For the next
week, Anna finds that her vision is blurry. Her vision is blurry because:
a) The fluid behind her eyes and nose has now been drained
b) The eye muscles are disturbed and so images at the fovea are no longer
clear
c) She can no longer use retinal disparity as a depth cue
d) She has lost some aqueous humor and the cornea cannot function correctly
Many people perceive the black diamonds in this picture as forming
a cube. The Gestalt principle that is most important to achieve
this perception is:
a) Closure
b) Proximity
c) Simplicity
d) Reversibility figure
The slanting lines are used as a depth cue. The slanting lines are an
example of:
a) Interpositions
b) Height in the visual field
c) Relative size
d) Linear perspective
The process of transduction occurs in
a) The photoreceptor cells
b) The optic nerve
c) The neurons in the visual cortex
d) The lens
Which of the following is a primary monocular depth
cue?
a) Interpositions
b) Texture gradient
c) Accommodation
d) Convergence
Benita plans to carry out research into different eye problems and their effects
on depth perception. Benita must
A. match the names of her participants with their results in her report.
B. inform participants of their obligation to disclose all relevant information.
C. inform participants that they are not allowed to withdraw from the research.
D. ensure that her participant’s personal details are not exposed.
Philip is conducting research on children who have a particular eye disorder.
His theory is that children with this eye disorder are unable to perceive the
Müller-Lyer illusion. He conducts a study with two groups: one group of
children with the eye disorder and a second group of children without the
eye disorder. The two groups are matched on age, sex and intelligence.
In this research design, the group of children with the eye disorder is the
___________ group and the group of children without the eye disorder is the
__________ group.
A. experimental; control
B. control; experimental
C. random; stratified
D. stratified; random
SHORT ANSWER QUESTIONS
Allan lives near the You Yangs and Barbara lives
in Baccas Marsh. Both of them are psychology
students who live in houses high up on a hill.
There houses are nearly 25 kilometres apart.
They ring each other and agree to turn all the
house lights off. Over the next 10 minutes Alan
lights a candle 10 times. Barbara notices a
change 6 times.
What is an absolute threshold?
Identify a way they could measure a JND?
SHORT ANSWER QUESTIONS
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Explain the processes of organisation and interpretation?
Trisha is researching the effect of context on visual perception.
She intends to show participants an ambiguous image that can be
interpreted as waves in the ocean or a bird’s face. Trisha selected
participants randomly from her target population and then
randomly allocated them to two experimental groups. For each
group, she plans to use context to create a different perceptual
set; one of land and water, the other of animals.
a. Give an example that Trisha could use that will help
participants create a perceptual set in relation to this ambiguous
figure.
b. Outline one strength and one limitation of random sampling.
SHORT ANSWER QUESTIONS
James sustains an injury to his left eye, and has to
wear an eye patch for several weeks.
a.
Name a depth perception cue that James would
be unable to use.
b.
b. Name a non-pictorial depth cue that James
would be able to use and explain how this cue
would assist him to perceive depth.
SHORT ANSWER QUESTIONS
a. Clearly state how the Ames room is constructed in terms of
its shape and the position of the peephole to create an
illusion.
b. Bernadette has never heard of the Ames room illusion while
Kane is familiar with the Ames room illusion and has an
understanding of why this illusion is thought to exist. Both
look through the peephole and watch a person walk from
one corner to the other.
What would you expect Bernadette and Kane to perceive?
Bernadette:
Kane: