1. Perception involves complex cognitive processes of selecting, organizing, and interpreting stimuli. It requires thinking, memory, and forming meaning from senses. 2. Perception is influenced by both objective external factors like intensity, size, movement of stimuli as well as subjective internal factors of the perceiver like motives, experiences, and culture. 3. There are different types of perception including form, size, motion, depth, and time perception that allow us to organize and understand our environment.

1. Perception
Lecture 8
Introduction
to Psychology (PSY-101)
Instructor: Raisa Munir

3. Perception
• Perception; is a complex cognitive process that is
concerned with selection, organization and
interpretation of stimuli.
• Perception involves cognitive process like thinking,
memory and ability to form meaning through the
sense processes.
• Perception is an active process in which sensory
experience is carried through the nervous system to
the brain and interpreted.

4. Difference between Sensation &
Perception
• Psychologists tend to view sensation as biological
process and perception as cognitive process.
• Both are interrelated .
• Sensation; refers to the process by which the sense
organ gathers information about the environment.
• Perception; is the process by which the brain organizes
and interprets sensations.

5. Factors of Perception
 There are two types of factors that affecting perception
1. Objective / external Factors
2. Subjective / internal Factors

6. Objective Factors
 There are a number of characteristics of stimuli
that influence our perception.
1. Intensity
2. Size
3. Distinct & Striking
4. Movement
5. Novelty
6. Duration
7. Repetition
8. Abrupt Change

7. Objective factors
• Intensity; The intensity of an external stimulus
determines its probability to being perceived.
louder a sound , the more likely a person is to
perceive it. The brighter a light ,the more likely
it is to be in the focus of perception.

8. • Size; a larger object is more likely to be
noticed than a smaller one. A full page
advertisement is more likely to be noticed
than a half- column one
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9. Distinct & Striking; distinct (clearly described)
and striking (attractive and unusual) things are
perceived sooner than dull and unclear things.

10. • Movement; When things move suddenly in
still and motionless environment ,it is quickly
perceived .e.g. birds sitting quietly on tree are
not quickly perceived as compared to ones
about to fly.

11. • Repetition; The more number of a time the
stimulus is repeated, the more it is likely to be
noticed. Repetition is one of the most
frequently used techniques in advertising and
is the most common way of attracting the
people’s attention. Frequency results in
making people aware of the stimulus.
• Duration; Television and radio advertisements
of long duration are attended to more than
those of short duration.

12. • Novelty; new object in a familiar situation
draw the perceiver’s attention. A new and
novel thing is perceived sooner than old and
used thing.
• Abrupt Change; Any change in stimulus
conditions, such as increase in noise , often
attracts attention.

13. Subjective Factors
 Sometimes, perception is determined not only by
the physical characteristics of stimuli but by the
characteristics of the perceiver. These are
1. Motives or needs
2. Interests & values
3. Past experience
4. Age
5. Preparatory set
6. Social & cultural factors

14. 1. Motives or Needs; when people are motivated
,they tend to see and hear what they want to hear.
In other words, we may be set to perceive the world
in ways that agree with our motives and match our
goals.
People at different levels of needs and desire
perceive the same thing differently. Power
seekers are more likely to notice power related
stimuli. That is to say expectancy, motives or interest
also affect people perception.

15. Subjective Factors
2. Interests & Values; we attend to those aspects of
world that relate to our interest.
3.Past Experience; Experience and knowledge have
a constant bearing on perception. Successful
experiences enhance and boost the perceptive
abilities and lead to accuracy in perception of a
person. Much of our daily activity is dependent
upon past experience. we have learned to react to
cues & symbols. E.g., on seeing a moving line on
the sky, we guess it to be an airplane.

16. Subjective Factors
4. Age; Age brings a change in perception as
well. A child perceives things in different
way as compared to a young person.
5.Preparatory Set; This refers to a person’s
readiness to respond to one kind of sensory
input, but not to other kinds.
6.Social & Cultural Influences ; The normal
perceptual experiences of a culture may
lead its members to develop perceptual
biases, suggestions and prejudices.

17. Kinds/Types of Perception
 We perceive objects in different manners as
compared to their position in the environment.
Objects may be moving or static, when we have to
perceive motion. We may have to locate sounds
and voices in the space around us. Lets look at:
1. Form Perception
2. Size Perception/ Perceptual Constancy
3. Motion Perception
4. Depth Perception
5. Time Perception

18. Form Perception
• Our perception is a unified experience. We are
familiar to organizing things in our mind into
a form, shape , a melody or a scene that
makes up a meaningful whole.
.

19. 1.Figure /Ground;
• we see objects and forms
of everyday experience as
standing out from the
background. e.g., a clock
hanging on the wall is
perceived as the figure,
while the wall is the
ground
• Our first perceptual
decision is what is the
image is the figure and
what is the background

20. • 2.Similarity; the tendency to group together
those elements that are similar in appearance.
• objects similar in appearance are perceived as
being part of same group
• 3.Proximity; The tendency to group together
those elements that are near to each other in
appearance.
• group objects that are close together as being
part of same group

21. • 4. Closure; The tendency to group according
to enclosed or complete figures rather than
open or incomplete ones.
• we fill gaps in if we can recognize it
• 5.Simplicity; The tendency to perceive a
pattern in the most basic ,straightforward
,organized manner

22. Size Perception/Perceptual Constancy
Size perception ; Size perception is the tendency to
perceive objects in a consistent manner despite the
changing sensations that are received by our senses.
visual constancy plays an important role in helping us
adapt to our environment successfully.
Learning plays an important role in the development of
constancy. Once we know that certain objects in our
environment have certain characteristics ,we tend to
perceive them in the same way, regardless of the
conditions under which they are perceived.

23. Size Perception
Three types of constancy are explained briefly
here:
1. Size Constancy
2. Shape Constancy
3. Color Constancy

24. Size Perception
 Size Constancy; When we know that
an object is of a certain size, we tend
to perceive it as being that same
size, regardless of how far it is from
our eyes.
 In Size constancy ,the perceiver has
the ability to judge true or measured
size, regardless of the distance
involved.
 E.g., when you finish a conversation
with a friend and he begins to walk
away ,the image on retina become
smaller & smaller. The knowledge
that he is also farther away,
compensates for change in retinal
image and you perceive him as the
same size.

25. Size Perception
2.Shape Constancy; When we know that
the object is a certain shape ,we tend
to perceive it as the same shape,
regardless of the viewing angle. We
have learned to make corrections in
our perception dependent on the
angle from which we observe.
• Everybody has seen a plate shaped in
the form of a circle. When we see
that same plate from an angle,
however, it looks more like an ellipse.
Shape constancy allows us to perceive
that plate as still being a circle even
though the angle from which we view
it appears to distort the shape

26. Size Perception
• 3.Color Constancy; Colors of
objects tend to remain
constant in perception when
we know their true color.
• refers to our ability to
recognize that color remains
the same regardless of how it
looks under different levels of
light. That deep blue shirt you
wore to the beach suddenly
looks black when you walk
indoors.

27. Motion Perception
 Motion Perception; Motion is perceived by
following the progressive change of an object’s
position in space with time. It has two types
1. Real Motion; The perception of the actual
movement of objects in the world is termed as
“real motion perception”.
• watching a ball thrown across your
field of view, you can easily perceive
that the ball is moving relative to the
world

28. 2: Apparent Motion; It is movement perceived
in the absence of physical movement of an
image across the retina
• looking at a neon street sign, where a series
of lights flash one after another, it appears to
move

29. Types of apparent motion
a) Induced Motion; - movement of one object
results in the perception of movement in
another object.
• have you ever seen the sun/ moon goes
behind a cloud? if so, you experience induced
motion.

30. • b). Phi Phenomenon; perceiving continuous
motion between separate objects viewed
rapidly in succession
• a string of lights across a house appear to
"run" even though you know it's just one light
turning off and the one next to it turning on
and so on down the line.

31. • C). Stroboscopic
Motion ; When a series
of still pictures is
presented in a rapid
succession so that we
perceive smooth,
coordinated movement
is called stroboscopic
motion. E.g., animated
movies & cartoons.

32. Motion Perception
d) Auto kinetic Motion; If we stare at a small
spot of light in a dark room for a few minutes,
it will appear to begin to move around
although the light is stationary; we see it
move randomly back and forth in the
darkness. While we don’t know the reason for
this positively, the auto kinetic effect may be
caused by the eye muscles moving to keep the
eye moist.

33. Depth Perception
Depth Perception ; the ability to judge the
distance of objects and the spatial relationship
of objects at different distances
There is a distance between the eyes so both eyes
receive different image on retina and the brain
integrates them into composite view.

34. Depth Perception
lets examine some of the cues we employ in
depth perception.
 Monocular Cues
 Binocular Cues
1.Monocular Cues; Cues that can operate when
only one eye is looking.

35. Depth Perception
2. Binocular Cues; Many of the cues for depth
require only one eye. In fact, one-eyed people,
under most conditions, have quite adequate
depth perception. Most of us look out at the
world with both eyes simultaneously and we
are thus able to add the binocular cues for
depth perception to the monocular ones.

36. Depth Perception
1.Retinal Disparity; When look at a particular
object, the two eyes do not receive exactly the
same image. The difference in the images in
the two eyes is called “ Retinal Disparity”.
2. Convergence; The eyes turn inward or
converge when we look at nearby objects. As
we fixate objects further away, the lines of
vision of the eyes tend to be almost parallel.

37. Time Perception
• We take time in seconds, minutes and hours which
pass into days, weeks, months , years and even
centuries. Time is also perceived in terms of past,
present and future.
• It refers to the subjective experience of time, which
is measured by someone's own perception of the
duration of the indefinite and continuous unfolding
of events. Another person's perception of time
cannot be directly experienced or understood, but
it can be objectively studied and understood
through a number of scientific experiments