Learning Activity 10
Review questions: suggested answers
1 The artist also uses the depth cues of:
• interposition; for example, the subjects in the foreground cover some of the scene behind
them, thereby giving the impression of depth.
• relative size; for example, the subjects who are ‘nearer’ are painted larger than those who
are ‘further away’.
• height in the visual fi eld; for example, the ‘more distant’ people and objects have been
placed higher in the painting by the artist than those that are perceptually ‘closer’.
2 A person with only one eye would have difficulty walking downstairs. The person would be
unable to use retinal disparity to judge depth, and although his one eye would turn inward
(by convergence), it would not be as useful in assessing depth as if two eyes were in use.
His performance might initially be diminished in this task, but because most depth cues are
monocular, he would soon learn to use other cues to negotiate going downstairs.
3 Accommodation is the depth cue that uses information associated with lens shape. As a
jeweller looks for a watch part on the shelf, his lenses are elongated; however, as he moves
the part in close to his eye to repair the watch, the lenses bulge to bring the part into focus
(by fitting the part’s image on the retina).
4 The retina receives a two-dimensional image. Depth cues from the environment (such as
linear perspective and interposition) and from inside our body (such as the messages from
the muscles that turn the eyes inwards in convergence) provide information to the brain to
help translate the 2-D retinal image into a three-dimensional perception.
Learning Activity 16
Review questions: suggested answers
1 Visual constancy refers to the tendency to perceive a visual stimulus as remaining stable and
unchanging despite any changes that may occur to the image cast on the retina.
2 Size constancy refers to the tendency to perceive a visual stimulus as maintaining its size,
despite changes to the image it casts on the retina. For example, as your cat walks towards
you, the image it casts on your retina increases in size. Yet you perceive the cat’s size as
unchanging due to size constancy (as well as depth cues and your familiarity with the
cat’s size).
b Size constancy may be difficult to use when depth cues are absent or misleading. For
example, a close short person and a more distant tall person cast similar-sized retinal
images. However, if depth cues are removed, (say in a photo or in a dark tunnel) it is
difficult to judge whether the person is tall or short, or close or distant.
3 a Shape constancy refers to the tendency to perceive a visual stimulus as remaining the
same shape despite any changes in the shape of the image cast on the retina.
b A small child may have trouble maintaining shape constancy when at a distance from an
object or at an extreme angle to it. For example, if a child were on the end of a long front
row at the cinema, they may have trouble maintaining the shape constancy for the images
of figures on the screen.
4 Brightness constancy refers to the tendency to perceive an object as maintaining its level of
brightness relative to its surroundings, despite changes in the amount of light reflected from
it onto the retina. For example, as you sit in the classroom focusing on the white shirt of the
boy in front, the room becomes duller as the sky outside clouds over. You still perceive his
shirt to be the same brightness, because its change in brightness has been the same relative
to other objects in the room.
5 Orientation constancy refers to the tendency to visually perceive the true orientation
(position) of objects in the environment even though the retinal image of the object may be
different in orientation. For example, when you lie on the floor looking up at the TV, although
your head is tilted and the TV’s retinal image is sideways, you understand that the TV and the
figures on it are upright, not tilted.
6 It is likely that visual constancies are mostly learned. Small babies give a startled response
as objects come towards them and the retinal image increases in size. Later, through
experience, the baby learns the game of the same-sized object getting closer and closer to
its face. Learning constancies clearly depend on learning other cues as well; for example,
distance cues for size constancy and familiarity of objects for size and shape constancies.
Constancies must develop as children develop. For example, orientation constancy would
improve as the child begins to move about in its environment.
Learning Activity 21
Review questions: suggested answers
1 a Perceptual set is a perceptual bias, predisposition or readiness to perceive a stimulus in
accordance with expectations. It can bias our perception so that we perceive what we think
we should see, rather than exactly what is there.
b Because we select certain parts of the visual stimulus to be organised and interpreted, and
ignore others, perceptual set is sometimes referred to as expectancy.
c For example, my mother drives a small green car. Recently I was waiting for my mother to
pick me up at the station, and as a small green car slowed, I waved and went to get in, only
to realise it was not my mother, but a stranger in the car. I had expected the small green
car to be hers, and had focused only on the small green car and not the person in it. My
perceptual set had interfered with the accuracy of my visual perception.
2 a Context is the environment or setting in which a visual stimulus occurs.
b Context can affect visual perception by creating a perceptual set. For example, you may
perceive a scene differently when you see two men threatening each other with knives:
first in the Drama room at school, and secondly in the street outside a nightclub. Because
of the context and your expectations, you would be less surprised or shocked if you saw it
in the Drama room than on the street.
3 a Past experience refers to the personal experiences that have occurred in someone’s life.
b Past experience can affect visual perception by creating a perceptual set. The experiment
by Bruner and Postman (1949) demonstrates this. They showed subjects a display of
playing cards for a few seconds. Subjects were asked to report the number of aces of
spades that they saw. Most reported seeing three, but in fact there were five. However two
of the aces of spades were coloured red. Because of their past experience with decks of
cards, subjects overlooked the red aces but perceived the black ones. Their perceptual set
had interfered with the accuracy of their visual perception.
Psychology VCE Units 3 & 4
Organisation in visual perception
© Macmillan Education Australia 2005. Unauthorised copying prohibited.
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Learning Activity 24
Review questions: suggested answers
1 A visual illusion is a misinterpretation (distortion or mistake) of real visual sensory stimuli.
2 A perceptual compromise occurs when two or more visual cues conflict with each other and,
when interpreting visual information, we tend to take account of the information provided by the
different cues. This results in a compromised interpretation of the conflicting cues and, therefore,
an illusion results.
3 Day (1989) believes that certain features of the stimulus provide conflicting cues, and rather than
favour one set of cues, we use both to create the incorrect interpretation of the visual stimulus—
and illusion.
4 Poggendorf illusion: one set of cues shows us vertical parallel lines, the other two lines that
exit the vertical line at different points. The compromised interpretation is that the diagonal
line is discontinuous.
Zöllner illusion: one set of cues shows parallel vertical lines, and another shows crosshatched
smaller lines in alternating directions. The compromised interpretation is that the
vertical lines are not parallel, but lean in alternate directions.
Hering illusion: one set of cues shows four horizontal parallel lines and another set of cues
shows a set of radiations from a focal point between the two middle lines to the extreme
lines. The compromised interpretation is that the horizontal lines are not parallel, but that the
middle two bulge away from each other near the focus.
Learning Activity 26
Review questions: suggested answers
1 The Ames room is a trapezium-shaped room, long on one side, shorter on the other and
angled away from the observer so that it looks like a normal rectangular room when viewed
with one eye (monocular).
2 As a person walks from the back right to the back left corner of the Ames room, they appear to
shrink. This is because the subject is actually moving further away from us, but also because the
room appears rectangular, and our brain maintains the shape constancy (of the room) in
preference to size constancy (of the subject).
3 The observer’s view is restricted to a monocular one, so that binocular depth cues are
unavailable. If the observer were able to use binocular cues, the illusion would fail.
4 According to apparent distance theory:
• the two back corners appear equidistant (produce the same visual angle) from the
observer, but one is actually twice as far away
• perceived sizes of objects are determined by the retinal image size when objects are
equidistant from the observer
• the object that casts the larger retinal image (the one in the physically nearer corner) is
perceived as larger than the one in the opposite, more distant corner.