This document discusses sensation and perception. It defines sensation as the electrochemical messages transmitted from sense organs to the brain in response to stimulation from the environment. Perception is defined as the brain's processing and interpretation of sensory information. The document outlines several key concepts in sensation and perception, including transduction, feature detectors, and the perceptual process of sensation, selection, organization, and translation. It also discusses factors that can influence perception such as those in the perceiver, target, or situation. Gestalt laws of grouping like proximity, similarity, closure, and symmetry are presented as influencing perceptual organization.

1. Sensation and
Perception
DR Mohamed Youssef Abuzied

2. Sensation & Perception
“ The study of perception is concerned with identifying
the process through which we interpret and organize
sensory information to produce our conscious experience
of objects and object relationship.”
We are now turning our attention to the topic of
“Sensation & Perception,” a specialty area within
Psychology that works at understanding how our senses
work & how we perceive stimuli in the environment. So,
with no further delay….

3. Let’s begin with some
basic definitions…
 S ense – Physical system that receives physical
stimulation from surrounding environment and
translates that stimulation into an electrochemical
message
 S ensation – The electrochemical message in
neurons transmitting information from the sense
organ to the brain.
 P erception – Processing of information done by the
brain – mental processes that organize and interpret
sensory information that has been transmitted to the
brain.

4. Transduction
 So the brain’s “language” is
electrochemical!
 All senses involve something called receptor
cells. Their job is to transduce (transform or
even “translate”) physical
stimulation/physical energy from the
environment into electrochemical messages
that can be understood by the brain.

5. The mystery of feature
detectors…
 Feature detectors are cortical neurons that
respond to specific features of a scene (e.g.,
particular edges, lines, angles and
movements)
 The brain then needs to assemble the whole
image from these specific features.
 “…perceptions arise from the interaction of
many neuron systems, each performing a
simple task.”

6. Perception
“ Perception is the process of receiving information about and making
sense of the world around us. It involves deciding which information
to notice, how to categorize this information and how to interpret it
within the framework of existing knowledge.
“ A process by which individuals organize and interpret their sensory
impressions in order to give meaning to their environment.
6 Organizational Behavior /
Perception

7. Perception Defined
 The process by which we become aware of objects and
events in the external world.
 The process of making sense of the world around us.
 Many people ignore the fact that all of us are different
and that these differences equip us to view the world
from our very own vantage points. Usually we spend
more energy defending our own position than
understanding others.
Where does the triangle
begin?

8. The Perceptual Process
1. Sensation 3. Organization
– An individual’s ability to – The process of placing
detect stimuli in the selected perceptual
immediate stimuli into a
environment. framework for
1. Selection “storage.”
– The process a person 3. Translation
uses to eliminate some – The stage of the
of the stimuli that have perceptual process at
been sensed and to which stimuli are
retain others for further interpreted and given
processing. meaning.
8 Organizational Behavior /
Perception

9. Factors influencing perception
A number of factors operate to shape and sometimes
distort perception. These factors can reside in the
perceiver, in the object or target being perceived or in
the context of the situation in which the perception is
made.
9 Organizational Behavior /
Perception

10.  Factors influencing Perception
Factors in the perceiver
• Attitudes
• Motives
• Interests
• Experience
• Expectations
Factors in the situation
• Time Perception
• Work Setting
• Social Setting Factors in the Target
• Motion
• Sounds
• Size
• Background
• Proximity
10
• Similarity Organizational Behavior /
Perception

11. Perceptual organization
 It is the process by which we group outside stimuli into
recognizable and identifiable patterns and whole objects.
 Certain factors are considered to be important contributors on
assembling, organizing and categorizing information in the
human brain. These are
- Figure ground
- Perceptual grouping
11 Organizational Behavior /
Perception

12. Perceptual organization
 Three Principles of Organization:
– A) Binary Opposition (all things in pairs)
 male/female, short/tall, white/black, good/bad
– B) Already formed social categories
 101 students, sorority sisters, UK basketball players,
Italians
– C) We also organize by similarities
 size (big buildings), color (things that are purple),
space (things from Hawaii), smell (things that
make us hungry), function (computer, phone, TV,
DVD, VCR, CD player, pager, palm)

13. The Cognitive Approach emphasizes
that people are shaped (& differ. from
each other) because their perceptions &
their thought processes differ. So
understanding some background
information on how we perceive things
in our environment may help assist us in
our understanding of the Cognitive
approach.

14. Schemas and Perceptual
Set
A perceptual set is…
 A mental predisposition to perceive
one thing and not another”
 This is based on experiences,
assumptions and expectations.

15. What shapes our
perceptual sets?
 What things do you think might affect our
perceptual sets (i.e., our tendency to
perceive things in certain ways)?
 Context effects
 Past experiences
 Effects of our culture

16. Schematas or Cognitive
Frameworks
 To eliminate the chaos of life (entropy) and help
make sense of the world, we simplify and reduce
our world
 We put our “selected” data in cognitive “folders”
– Also called: Schemata or Cognitive Frameworks

17. Schemas
 Another word used to describe perceptual set is
schemas.
 Schemas can influence our perception because we
tend to see things that we expect to see or wish to.
 We interpret things based on similar things we have
experienced in the past –this is called assimilation.

18. Schemas…..  Now what do you think
would happen if we receive
new information that
doesn’t not fit our
schemas?
 When we receive new
information we can ignore it
(!)
 or we can change our
Schemas are almost like a schemas to fit the new
box that we put information into. information. This is called
The way we organize compartments
in the box is based on things like our past experiences, accommodation.
contexts, etc. and this influences our perceptions!

19. Gestalt laws of grouping
 A major aspect of Gestalt psychology is that it
implies that the mind understands external stimuli
as whole rather than the sum of their parts. The
wholes are structured and organized using grouping
laws. These laws deal with the sensory modality
vision however there are analogous laws for other
sensory modalities . Through the 1930s and '40s
Wertheimer, Kohler and Koffka formulated many of
the laws of grouping through the study of visual
perception.

20. Law of Proximity
 – The law of proximity states that when an
individual perceives an assortment of
objects they perceive objects that are close
to each other as forming a group. For
example, in the figure illustrating , we
perceive the collection of circles to be in
groups.

21. Law of Similarity
 – The law of similarity states that elements
within an assortment of objects will be
perceptually grouped together if they are
similar to each other. This similarity can
occur in the form of shape, colour, shading
or other qualities .

22. Law of Closure
 – The law of closure states that individuals
perceive objects , as being whole when they
are not complete. We tend to complete the
incomplete Specifically, when parts of a
whole picture are missing, our perception
fills in the visual gap. The purpose of
completing a regular figure is in order to
increase the regularity of surrounding
stimuli.

23. Law of Symmetry
 – The law of symmetry states that the mind
perceives objects as being symmetrical and
forming around a center point. It is
perceptually pleasing to be able to divide
objects into an even number of symmetrical
parts. Therefore, when two symmetrical
elements are unconnected the mind
perceptually connects them to form a
coherent shape.

24. Law of Common
Fate
 – Objects are perceived as lines that move
along the smoothest path. We perceive
elements of objects to have trends of
motion, which indicate the path that the
object is on. The law of continuity implies
the grouping together of objects that have
the same trend of motion and are therefore
on the same path.

25. Law of Continuity
 – The law of continuity
 states that elements of
 objects tend to be grouped
 together, and therefore
 integrated into perceptual wholes if they are
aligned within an object . We are less likely
to group elements with sharp abrupt
directional changes as being one object.

26.  The sense-datum theory can say,
however, that we areindirectly aware
of ordinary objects: that is, aware of
them by being aware of sense-data.

27. The Naive Theory of
Perception (A.K.A: Direct
Realism)

28. The Not-so-Naive Theory
of Perception (AKA:
Indirect Realism)

29. The Not-so-Naive but
Totally Crazy Theory of
Perception (AKA: Idealism)

30. What is Attention?
 ability to focus on a task
 ability to concentrate
 refers to the allocation of processing
resources

31. Attention
 In daily language it refers to
concentration
Attention has two broad dimensions :
a- selectivity b- intensity

32. Attention
 Quality of information processing :
 Perception ,processing and storing of
information wit a good intensity
 So Attention can be defined as the
state of the processing system that is
optimally tuned in terms of selectivity
and intensity

33. Attentional Behavior
 Now more dimensions will appear
 E.g. Divided Vs Sustained attention

34. Different Aspects of
Attention
 selective attention
 divided attention
 automaticity

35. Selective Attention
 Difficult to attend to more than one
thing at the same time
 Trying to attend to one task over
another requires selective attention
 Selective Attention (Visual)
 slower to name color when word says
a different color than to name the color
of an colored square

36. why does this happen?
– reading is an automatic process
– color naming is a controlled process
– automatic process of reading interferes
with our ability to selectively attend to ink
color

37. Selective Attention
(Auditory)
 Dichotic listening
 In a typical dichotic listening task, Ss
hear two messages
simultaneously...one message in one
ear and one message in the other;
 As they are listening, they are asked
to 'shadow' one of the messages (i.e.
repeat back the words from one
message only

38. Theoretical Interpretations
of Selective Attention
 Bottleneck theories or filter theories
 bottleneck is a mechanism that limits
the amount of information to be
attended to
 what gets through? what is selected
and when?

39. Early selection
 Broadbent (1958) proposed that
physical characteristics of messages
are used to select one message for
further processing and all others are
lost .He postulated that the many
signals entering the central nervous
system in parallel are held for a very
short time in a temporary “buffer.”

40. Attenuation
 Treisman (1964) proposed that
physical characteristics are used to
select one message for full processing
and other messages are given partial
processing

41. Late selection
 Deutsch & Deutsch (1963) proposed
that all messages get through, but that
only one response can be made (late
selection)

42. Divided Attention and
Dual Task Performance
 trying to attend to two stimuli at once
and making multiple responses rather
than making one response to multiple
stimuli (interference)

43. Sustained attention:
vigilance
 Sustained attention, or vigilance, as it
is more often called, refers to the state
in which attention must be maintained
over time.

44. Two-process” theories of
attention.
 Controlled search and automatic
detection.
 Controlled search is easily
established and is largely under the
individual’s control in that it can be
readily altered or even reversed. It is
strongly dependent on the stimulus
load. It has been suggested that it
uses short-term memory.

45. Automatic Detection .
 By contrast, automatic detection, or
automatic processing, operates in
long-term memory and is dependent
upon extensive learning. It comes into
operation without active control or
attention by the individual, it is difficult
to alter or suppress.

46. Broadly speaking, the two types of
attention can be characterized as
focal and automatic .
 Someone who is focally attentive is
highly aware, consciously in control,
and selective in handling sensory
phenomena. A person in such a state
also uses the brain for short-term
storage. Focal attention makes great
demands on brain capacity

47.  Automatic attention makes fewer
demands but is relatively inflexible, as
it cannot cope with the unexpected.

48.  The focal and automatic modes may
be illustrated by a driving example: a
new driver has to attend to gear
shifting in a focal way (actively thinking
about it), while an experienced driver
changes gears automatically (not
needing to think about it).