Visual perception

Visual Perception
Individual Differences, Purposes and
Needs
 Conformity may sometimes influence perception. Sometimes,
influenced by a group or crowd we tend to see things as the group sees
it.

 Some factors related to personality may have an influence on perception.
One such factor is 'tolerance of ambiguity'. Some people can tolerate
randomness more than others. They can accept and live with disorder.
Others can not. They must create order.

 People tend to have various levels of prejudice. Some people prefer
simplicity and clarity. Others can tolerate and function well with variety.

 Prejudice can affect perception as Gordon Allport and Leo Postman
showed in a famous study (1945). After briefly looking at a drawing of
figures inside an underground train - five men, two women and a baby,
with two of the men standing - a black man and a white man face-to-face
in the centre of the picture. Observers were asked to describe what they
had seen. Over half of the observers reported having seen a cut-throat
razor in the hands of the black man. Some even claimed that he had been
'brandishing it widely' or 'threatening' the white man whereas it was
actually in the left hand of the white man standing with him. This

experiment was part of a study of rumour so memory as well as
perception was involved.

 impulsivity vs. reflectivity. When asked to find a match for a 'familiar
figure' (such as a drawing of a telephone) from a choice of 6, some
people seem habitually 'leap in' with a response before checking the
alternative fully - these are the impulsives - whilst others seem unwilling
to respond until they are sure that they have made the correct choice these are the reflective types.

 Another kind of cognitive style was referred to as 'field dependence or
independence’. Field independence refers to an aptitude for
disembedding figures from their contexts. This means they have a
high sense of discrimination and can identify something they are
searching for in a confusing field.
o Someone who finds words easily in word-search grids has
considerable field independence.
o Where's Wally? books in which one has to find a recurrent
character amidst a crowd of people and a frenzy of depicted
activity on a very detailed double-page spread.
o Those who are good at this are field independent.
o Similarly children's puzzles sometimes include the task of
identifying faces, objects or animals 'hidden' in a relatively
detailed
 Gender plays a part in perception too. One gender-related influence
concerns how our attention may be drawn to different aspects of a scene
or image.
 Using ambiguous doodle-like black-and-white figures found gender
differences in interpretation.

• A figure which was more likely to be viewed as a
brush or a centipede by males was more likely to be
viewed as a comb or teeth by females.
• Another figure viewed as a target mostly by males
was more likely to be viewed by females as a dinner
plate.
• And a third figure which was viewed mostly by men
as a head was viewed mostly by females as a cup.

Other roles can also influence perception. An aerial
photograph of a river delta may appear obvious to a
geographer or a pilot, but if the image lacked an explicit
label, others might have quite different interpretations. What
is Corvus corax to a professional ornithologist is simply a
pest to some farmers, an ill omen to the superstitious, 'Old
Grandfather' to the Koyukon Indians of the subarctic forest
of North America, a crow to most of us, and a raven to the
amateur naturalist.

 Many factors which play a part in influencing how things are perceived
are relatively 'stable' or long-term individual factors. These include
personality, cognitive styles, gender, occupation, age, values, attitudes,
long-term motivations, religious beliefs, socio-economic status,
cultural background, education, habits and past experience.
o But there are other factors which may contribute to individual
differences in perception which are more transitory. These include
current mental 'set', mood (affective/emotional state), goals,
intentions, situational motivation and contextual expectancies.

 WE mentioned the subjectivity of the photographic image It is worth
reminding ourselves that photographs reflect not only the scene they
depict but the purposes of the photographer. A photograph is a
particular photographer's selection from the world of something which
they regarded as significant for some reason and is framed in a way which
reflects certain considerations. Such purposes include:
making a record of something
 aesthetic reasons - the subject and/or the framing
seemed aesthetically interesting (e.g. 'beautiful')
 'self-expression' - to express how they felt about
something
 persuasion (social/political) e.g. to shock
Furthermore, each photograph alludes to photographic conventions:









of a particular historical period
for photographs of particular types (e.g. news photos,
snapshots, portraits, passport photos)
composition/framing, lighting, point of view
of other photographs by the same photographer

Thematic Apperception Test (TAT) cards are sometimes
used in psychoanalysis as a way of exploring the thoughts

and feelings of the person interpreting the ambiguous but
figurative situational images depicted on the card. The scenes
depicted are emotionally charged but open to interpretation
in a variety of ways. The use of such images acknowledges
the role of personal concerns in perception.
Mood may also influence perception. Leuba and Lucas
(1945) conducted an experiment involving the description of
6 pictures by 3 people when in each of 3 different moods.
Each mood was induced by hypnosis and then the pictures
were shown. Here are the descriptions that one person gave
for a picture of 'four college men on a sunny lawn, listening
to radio':






Happy mood: 'Complete relaxation. Not much to do just sit, listen and relax. Not much at all to think
about.'
Critical mood: 'Someone ruining a good pair of
pressed pants by lying down like that. They're
unsuccessfully trying to study.'
Anxious mood: 'They're listening to a football game or
world series. Probably a tight game. One guy looks as
if his side wasn't winning.'

We need to remind ourselves that it was the same picture
each time. Mood can clearly play an important part in
perception.
Albert Hastorf and Hadley Cantril (1954) conducted what
became a famous study of the reactions of opposing fans to
an American football game between two university teams the Princeton Tigers and the Dartmouth Indians (Princeton
won). It was a rough and tense game. One Dartmouth player
was taken off with a broken leg and a star Princeton player
suffered a broken nose. Both sides were penalized.
Undergraduate students from each of the universities were
asked for their reactions to the game a week later.
69% of the Princeton students who had seen the game saw it
as 'rough and dirty' compared to only 24% of the Dartmouth
supporters, whilst 25% of the Dartmouth students invented
their own category of 'rough and fair'. When shown a film of

the game later, the Princeton students 'saw' the Dartmouth
team make over twice as many rule infractions as were seen
by Dartmouth students. Hastorf and Cantril comment that:
The data here indicate that there is no such 'thing' as a
'game' existing 'out there' in its own right which
people merely 'observe'. The game 'exists' for a person
and is experienced by him only insofar as certain
happenings have significances in terms of his purpose.
For these students, the perception and recall of what might
seem to be 'the same event' involved a very active
construction of differing realities. Hastorf and Cantril's
classic case-study emphasizes the crucial role of values in
shaping perception.

Context and Expectations
Someone once said that there is no meaning without context.
Various kinds of context are important in shaping our
interpretation of what we see. As a reminder of the
importance of making clear what is meant by the importance
of 'context' in perception I briefly list here several very
different uses of the term. However, I would not suggest that
in practice tidy distinctions can always be usefully made.
The largest frame is that of the historical context of
perception. Some theorists, such as Marshall McLuhan
(1962), Walter Ong (1967) and Donald Lowe (1982), have
argued that there have been shifts over time in the human
'sensorium' - that is, in the 'balance' of our senses or the
priority which we give to some compared with others. Such
argue that in western urban cultures we have come to rely
more on sight than on any other sense (this was referred to in
Visual Perception 1 as 'ocularcentrism').
Another major framework is that of the socio-cultural
context of perception. Just as there may be subtle differences
in human perception over time there may also be differences

attributable to culture. Some of these were alluded to in
Visual Perception 3. Constance Classen (1993) in her book
Worlds of Sense shows that different cultures accord priority
to different senses - the Ongee of the Andaman Islands, for
instance, live in a world ordered by smell.
A native American Indian writer called Jamake Highwater,
who is of Blackfeet/Cherokee heritage, draws attention in the
following extract to radically different ways of seeing the
world:
Evidence that Indians have a different manner of
looking at the world can be found in the contrast
between the ways in which Indian and non-Indian
artists depict the same events. That difference is not
necessarily a matter of 'error' or simply a variation in
imagery. It represents an entirely individual way of
seeing the world. For instance, in a sixteenth-century
anonymous engraving of a famous scene from the
white man's history an artist depicted a sailing vessel
anchored offshore with a landing party of elegantly
dressed gentlemen disembarking while regal,
Europeanized Indians look on - one carrying a 'peace
pipe' expressly for this festive occasion.
The drawing by an Indian, on the other hand, records a
totally different scene: Indians gasping in amazement
as a floating island, covered with tall defoliated trees
and odd creatures with hairy faces, approaches.
When I showed the two pictures to white people they
said in effect: 'Well, of course you realize that what
those Indians thought they saw was not really there.
They were unfamiliar with what was happening to
them and so they misunderstood their experience.' In
other words, there were no defoliated trees, no floating
island, but a ship with a party of explorers.
Indians, looking at the same pictures, pause with
perplexity, and then say, 'Well, after all, a ship is a
floating island, and what really are the masts of a ship

but the trunks of tall trees?' In other words, what the
Indians saw was real in terms of their own experience.
The Indians saw a floating island while white people
saw a ship. Isn't it also possible - if we use the bounds
of twentieth-century imagination - that another, more
alien people with an entirely different way of seeing
and thinking might see neither an island or a ship?
They might for example see the complex networks of
molecules that physics tells us produce the outward
shapes, colours and textures that we simply see as
objects. Albert Einstein showed us that objects, as well
as scientific observation of them, are not experienced
directly, and that common- sense thinking is a kind of
shorthand that attempts to convert the fluid, sensuous
animation and immediacy of the world into illusory
constructs such as stones, trees, ships and stars.
We see the world in terms of our cultural heritage and
the capacity of our perceptual organs to deliver
culturally predetermined messages to us. (Highwater
1981, 6-8)
Both the historical and socio-cultural context of perception
are vast themes which will not be explored further here, but
such studies do help to emphasize that 'the world' is not
simply indisputably 'out there' but is to some extent
constructed in the process of perception. Within a given
socio-cultural context, there are widely-shared interpretive
conventions and practices. Whilst the basic processes of
human perception are largely universal there is scope for
subtle but significant variations over space and time.
Several other kinds of context are commonly referred to. I
have referred already, in Visual Perception 3, to the
importance of individual factors which can have an influence
on perception. An emphasis on the individual as a context
emphasizes the role of the various long-term characteristics
of individual perceivers such as values, attitudes, habits and
so on. An emphasis on the situational context considers such
transitory situational factors as goals, intentions, situational
constraints and contextual expectancies. Finally, an emphasis

on the structural context stresses structural features and
relationships (such as the relationship between one line and
another) 'in' what is perceived - though the extent to which
there is agreement about even such low-level formal features
may vary.
Five main definitions of the scope of the term 'context' have
been listed here in relation to their potential influence on
perception:






historical
socio-cultural
individual
situational
structural

Whilst it may be useful to be alert to the very different
meanings that the word 'context' can have, disentangling
them is problematic.
A very well-known study by Bugelski and Alampay (1961)
can be seen as showing the importance of situational context.
Their experiment is often used as an example of the influence
of what psychologists call 'perceptual set': a predisposition to
perceive something in relation to prior perceptual
experiences. Perceptual set is broader than situational
context, since it may involve either long-term (for instance,
cultural) prior experience or, as in this case, short-term or
situational factors (Murch 1973, 300-301). Groups of
observers in the experiment were shown an ambiguous line
drawing which was designed to be open to interpretation
either as a rat or as a bald man wearing spectacles. Prior to
seeing this image, two groups were shown from one to four
drawings in a similar style. One group was shown drawings
of various animals and the second group was shown
drawings of human faces (see illustration below). A control
group was shown no pictures beforehand. 81% of the control
group reported seeing the ambiguous image as a man rather
than a rat. The more pictures of animals that the 'animal'
group had seen, the more likely they were to see a rat rather
than a man (with 4 prior images of animals 100% then saw a

rat). From 73-80% of the 'faces' group subsequently saw a
man rather than a rat.

The influence of perceptual set has also been explored in
relation to the famous image shown below:

This image was designed to be interpreted as either a young
woman or an old woman. It was introduced into the
psychological literature by Edwin G Boring (1930) (though it
was published by the British cartoonist W E Hill in 1915, and
is thought to be based on a French version of 15 years
earlier). It is sometimes given the chauvinistic label of 'The
Wife and the Mother-in-Law'. In order to study the role of
perceptual set Robert Leeper (1935) had the image redrawn
in two 'biased' forms: one which emphasized the old woman
and the other which emphasized the young woman (see
image below).

Leeper varied the conditions of viewing for five groups. A
control group was shown only the ambiguous drawing, and
65% of this group spontaneously described the image as that
of a young woman. The second and third groups were first
given a verbal description of the old woman and the young
woman respectively. The fourth and fifth groups were first
shown the 'old' version and the 'young' version respectively.
Groups 2 to 5 were then shown the original ambiguous
image. Leeper found that each of the primed groups was
'locked-in' to their previous interpretation. 100% of group 5,
which had seen the young version first, interpreted the
ambiguous image as a young woman. 94% of group 4, which
had seen the old version first, reported seeing the old woman
in the ambiguous image. The percentages opting for each
interpretation amongst those given verbal descriptions were
much the same as for the control group. Gerald Murch (1973,
305) was unable to replicate these findings (94% of his
control group first saw the young woman) and suggested that
the image was by then so well-known that this may have
influenced the results.
Particular situational contexts set up expectations in the
observer. Bruner and Postman (1949) conducted an
experiment in which playing-cards were used, some of which
had the colour changed from red to black or vice versa. The
cards were exposed in succession for a very short time.
Subjects identified them as follows:



some normalized the colours of the anomalous cards;
some normalized the suits to make them compatible
with the anomalous colours;



some compromised and saw the anomalous cards as
brown or purple.

Interpretation here was dominated by what the situational
context suggested that people ought to be seeing. A shorter
time of exposure was necessary for people to name the
normal cards than the anomalous ones.
In one experiment, Steven Palmer (1975) first presented a
situational context such as a kitchen scene and then briefly
flashed on a target image. When asked to identify a loaf-like
image, people who had first seen the kitchen correctly
identified it as a loaf 80% of the time. Obviously, a loaf of
bread is the kind of thing you’d expect to find in a kitchen.
They were asked to identify an image like an open US
mailbox and an image resembling a drum - two objects not
usually associated with the kitchen. The images were a little
ambiguous: the mailbox was a little like the shape of a loaf
with a slice of bread lying next to it, and the drum could have
been interpreted as the lid of a jar. People who had first seen
the kitchen only identified these as a mailbox and a drum
40% of the time. The ability to identify objects was affected
by people’s expectations concerning what is likely to be
found in a kitchen.
I have mentioned that situational contexts generate certain
(short-term) expectations but it is worth noting in passing
that expectations may also be set up by longer-term
influences - such as by stereotypes, prejudices and past
experience.

To return to contexts, here is an example of structural
context. This pattern of circles is known as the Ebbinghaus
(or Titchener) illusion. It is an illusion of relative size (or
more strictly, area). Here the formal relationship between the

parts of the image leads the small white circle (which is the
same size in both images) to seem larger in the structural
context of the tiny black circles than amongst the large black
circles. There is no shortage of examples of the role of
structural context amongst the geometrical illusions which
can be found in psychology textbooks so no further examples
of the role of structural context will be discussed here.
At this point it is useful to introduce schema theory briefly. A
schema (plural 'schemata' or 'schemas') is a kind of mental
template or framework which we use to make sense of
things. Particular circumstances seem to activate appropriate
schemata, which set up various standard expectations about
such contexts. Such schemata develop from experience. They
help us to ‘go beyond the information given’ (as Jerome
Bruner famously put it) by making assumptions about what
is usual in similar contexts. They allow us, for instance, to
make inferences about things which are not currently directly
visible. The application of schemata and the expectations
which they set up represents 'top-down' processes in
perception (whilst the activation of schemata by sensory data
is a 'bottom-up' process). A good example of the role of topdown processes is where you think that you recognize
someone in the street and then realize (from sensory data)
that you are wrong. We are often misled in this way by
situational contexts, by wishful thinking and so on, ignoring
contradictory sensory data in favour of our expectations.
In an experiment by Brewer and Treyens (1981), individual
participants were asked to wait in an office. The
experimenter said that this was his office and that they
should wait there whilst he checked the laboratory to see if
the previous participant had finished. After 35 seconds, he
returned and took the participant to another room where they
were asked to recall everything in the room in which they
had been waiting. People showed a strong tendency to recall
objects consistent with the typical ‘office schema’. Nearly
everyone remembered the desk and the chair next to it. Only
eight out of the 30 recalled the skull (!), few recalled the
wine bottle or the coffee pot, and only one recalled the picnic
basket. Some recalled items that had not been there at all: 9

remembered books. This shows how people may introduce
new items consistent with the schema.
In an experiment by Baggett (1975) participants were shown
a series of simple line drawings telling a story. One story
showed a long-haired man entering a barbershop, then sitting
in the barber’s chair, and finally leaving the shop with
shorter hair. In a later test they also saw a picture showing
the actual haircut, which had not been present originally.
People were fairly good at remembering that this picture had
not been present if the test followed immediately after the
initial showing. However, if the test occurred a week after
the initial presentation most people claimed that they had
seen the haircutting picture in the original sequence. This
shows the way in which we incorporate in our memories
inferences derived from our schemata. This experiment was
concerned with memory rather than perception, but it is
difficult to separate these processes if you take the stance that
no perception is 'immediate'.

Gestalt Principles of Visual Organization
In discussing the 'selectivity' of perception I have alluded to
foregrounding and backgrounding. We owe the concept of
'figure' and 'ground' in perception to the Gestalt
psychologists: notably Max Wertheimer (1880-1943),
Wolfgang Köhler (1887-1967) and Kurt Koffka (1886-1941).
The Gestalt psychologists outlined what seemed to be several
fundamental and universal principles (sometimes even called
'laws') of perceptual organization. The main ones are as
follows (some of the terms vary a little):
 Proximity,
 similarity,


good continuation,

 closure,

 smallness,
 surroundedness,
 symmetry and
 prägnanz.
The principle of proximity can be demonstrated thus:

What you are likely to notice fairly quickly is that this is not
just a square pattern of dots but rather is a series of columns
of dots. The principle of proximity is that features which are
close together are associated. Below is another example.
Here we are likely to group the dots together in rows.

The principle also applies in the illustration below. We are more likely to
associate the lines which are close together than those which are further
apart. In this example we tend to see three pairs of lines which are fairly
close together (and a lonely line on the far right) rather than three pairs of
lines which are further apart (and a lonely line on the far left).

 The second major principle of perceptual organization - that of similarity.
Look at the example below.

Here the little circles and squares are evenly spaced both horizontally and
vertically so proximity does not come into play. However, we do tend to see
alternating columns of circles and squares. This, the Gestalt psychologists
would argue, is because of the principle of similarity - features which look
similar are associated. Without the two different recurrent features we would
see either rows or columns or both...

 A third principle of perceptual organization is that of good continuity.
This principle is that contours based on smooth continuity are preferred to
abrupt changes of direction. Here, for instance, we are more likely to
identify lines a-b and c-d crossing than to identify a-d and c-b or a-c and
d-b as lines.

 Closure is a fourth principle of perceptual organization: interpretations
which produce 'closed' rather than 'open' figures are favoured.

Here we tend to see three broken rectangles (and a lonely shape on the far
left) rather than three 'girder' profiles (and a lonely shape on the right). In this
case the principle of closure cuts across the principle of proximity, since if we
remove the bracket shapes, we return to an image used earlier to illustrate
proximity...

 A fifth principle of perceptual organization is that of smallness. Smaller
areas tend to be seen as figures against a larger background. In the figure
below we are more likely to see a black cross rather than a white cross
within the circle because of this principle.

As an illustration of this Gestalt principle, Coren, Ward and Enns (1994, 377)
argue that it is easier to see Rubin's vase when the area it occupies is smaller. The
lower portion of the illustration below offers negative image versions in case this
may play a part. To avoid implicating the surroundedness principle the
conventional broad borders from the four versions have been removed. The
Gestalt principle of smallness would suggest that it should be easier to see the
vase rather than the faces in the two versions on the left below.

 The principle of symmetry is that symmetrical areas tend to be seen as
figures against asymmetrical backgrounds.

 Then there is the principle of surroundedness, according to which areas
which can be seen as surrounded by others tend to be perceived as figures.

Now we're in this frame of mind, interpreting the image shown above should not
be too difficult.
 All of these principles of perceptual organization serve the overarching
principle of pragnänz, which is that the simplest and most stable
interpretations are favoured.
 The Gestalt principles of perceptual organization suggest is that we may
be predisposed towards interpreting ambiguous images in one way rather
than another by universal principles.

 The Gestalt principles can be seen as reinforcing the notion that the world
is not simply and objectively 'out there' but is constructed in the process of
perception

Visual perception

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Visual perception