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Cognition (mental activity or mental processes)

 Cognition (Latin: cognoscere, "to know" or "to
 recognize") refers to the acquisition, storage,
 transformation, and use of knowledge. Cognition
 can be natural or artificial, conscious or
 unconscious.
 It is a faculty of mental processes such as
 learning, memory, perception, thinking, problem
 solving, reasoning, decision making etc.
Characteristics
The cognitive processes are active, rather than
passive
The cognitive processes are remarkably
efficient and accurate
The cognitive processes Handle positive
information better than negative information
The cognitive processes are interrelated with
one another, they do not operate in isolation
many cognitive processes rely on both bottom-
up and top-down processing
Sensation and Perception

 Sensation
   The processes by which our sense organs
   receive information from the environment.
 Transduction
   The process by which physical energy is
   converted into sensory neural impulses.
 Perception
   The processes by which people select,
   organize, and interpret sensations.
Sensation & Perception Processes
sensation
Sensation is defined as:
Irreducible elements from which perceptions
are formed as experiences which are simpler
and less meaningful than perceptions and
uninfluenced by learning and other
psychological processes such as emotion and
motivation (Hebb, 1972; Scharf, 1975).
Problems of perception
No direct physical contact with the visual
elements is required to appreciate there nature.
How do we form the impressions of the
quantitative and qualitative aspects of external
objects?
Does the real physical world actually exist
independently of our experience? If so, how we
can come to know its properties and how truth
of that knowledge be determined?
Problems…

How percepts are constructed from the
interaction of physical energy (light) and the
perceiving organism.
Proximal and distal stimuli are different but
our perceptions are generally accurate or
veridical enough to adjust ourselves in the
environment.
Some times percept have properties
considerably different form proximal
stimulus.
Components of perception

Distal stimulus
Distal stimulus refers to a physical aspect of the
external environment, or the physical energy
which comes from the eternal source. For
example, object in the external environment
such as, table, fan etc.
Proximal stimulus
It refers to the physical energy coming from the
external source strikes on the sensory receptors.
Components…

Input and output
Input refers to the sensation of stimulus and
output refers to behavior made in response to
the input.
Percept
Out come of perception is known as percept.
Recognizing an object as flower would be an
example of percept.
Difference between proximal and distal
                 stimulus
Much of the light coming form distal source is
scattered by molecules and lost before it reaches
the receptors of the eye.
Resulting proximal image is much smaller,
inverted relative to the distal stimulus
Proximal stimulus is partly under the control of
observer’s head and eye movements.
Information in the form of electromagnetic
energy is changed in the neural impulses
(transduction).
Defining perception


According to Morgan and King, “perception is
the way the world look (sounds, feels, tastes
and smells too)”.
According to Zigher (1985), perception refers
to the interpretation of sensory information, as
a constructive and creative process which
endows sensory experience with meaning.
Defining…
Perception is a process by which
individuals organize and interpret their
sensory impressions in order give meaning
to their environment for making better
adjustment with it.
Perception is a process by which we
recognize and interpret or give meaning to
raw material provided by sensory system
with the help of other psychological
processes such as, learning, memory,
emotions and motivation.
Defining…
 Perception is the process of creating an
 internal representation of the out side world
 (internal representation is a joint product of
 bottom up and top-down processing).

 Perception is the interpretation of the
 information provided by sensory system.
Perception is active, selective and
relatively more automatic higher
mental process through which we
experience or interpret our
immediate surrounding.
Properties of perception

Perception is interpretation of physical
energy or giving meaning to it.
In perception, registered stimuli by the
senses are gathered and interpreted with the
help of previous knowledge.
Perception combines aspect of both the
outside world (the stimulus) and inner
world (previous knowledge).
Properties …
  Perception is relatively more automatic
  process, required less effort than other
  cognitive tasks, such as problem solving of
  decision making.
  Perception is influenced by other
  psychological processes such as motivation
  and emotion.
  Perception is an active mental process
  involves both top-down and bottom-up
  processing.
Concepts in perception

Physical- external or internal stimulus such
as wave length, intensity etc.
Physiological- stimulation of sensory
system: neural activity- excitation-
inhibition; sensory modality: transduction
Behavior
Subjective experience
Perception
Perceptual Organization
Perceptual Constancies
Depth and Dimension
Perceptual Set
The World of Illusions
Approaches to perception

Structuralism
Wilhelm Wundt and Edward Bradford
Titchner (1867-1927)
Structuralisms emphasized on the study of
the structure of perception. Its goal was to
uncover the simplest, most basic elements
of conscious experience (bottom-up
processing).
Constructivist Approach
Emphasized on the active nature of perceptual process.
Influenced by empiricism.
Proposed that the percept is more than the information
coming form stimulus.
Some constructive processes occur within the observer.
These are mediating processes between physical world
and its perception.
Our perception is a mental construction based on our
cognitive strategies, past experiences, biases,
expectations, motives, attention, and other personal
characteristics
Direct perception approach (James J.
          Gibson, 1904-1979)
Stimulus contains important information
necessary for perception
Past experiences are not important
Perception depends on the characteristics of
stimuli (subjective variables are not
important)
It is also known as ecological approach
because it focuses on the adaptive link
between the perceiving organism to its
physical environment.
Computational Approach
       (David Marr, 1945-1980)

Involves mathematically oriented analysis
of certain aspects of visual perception
derived form computer simulation and AI.
Accepts Gibson’s basic idea of direct
perception but also proposes that perception
of characteristics such as lines, edges,
borders, contours, motion, and other
discontinuity.
Beliefs of the information-processing
  approach
Information is processed in stages
Information is processed serially
The nature of information changes stage to
stage
Information processing is affected by several
factors (noise)
It uses both bottom-up and top-down processing
It is a mediating process between input and
output
Gestalt approach

(German: Gestalt - "shape" or "figure")
Berlin School
Kurt Koffka, Max Wertheimer, and Wolfgang
Köhler (students of Carl Stumpf) are the
founder of this school. The 'Gestalt' or 'whole
form' approach sought to define principles of
perception -- seemingly innate mental laws
which determined the way in which objects
were perceived.
Gestalt: Basic idea

Operational principle of the brain is holistic,
parallel, and analog, with self-organizing
tendencies
 “The whole is greater than the sum of the
parts"
Opposed to structuralism and Wundt
Gestalt effect refers to the form-forming
capability of our senses particularly visual
sense.
Figure and ground
Properties of figure ground
Figures hold more memorable association than
the ground.
Figures are seen as being in front of the ground.
The ground is seen as uniformed material and
seems to extend behind the figure.
The contour separating the figure from the
ground appears to belong to the figure.
Compared to ground, perception of figure is
effortless
Field forces

Cohesive forces
Restraining forces
∑ C = ∑ R = no perception (Ganzfeld)
∑ C > ∑ R = perception
∑ C < ∑ R = unclear or unstable perception
Laws of pragnanz

The fundamental principle of gestalt
perception is the law of prägnanz (German
for pithiness).
The physiological organization will always
be good. Good refers to the simplest and
most stable.
We tend to order our experience in a
manner that is regular, orderly, symmetric,
and simple.
Gestalt laws of perceptual organization

Gestalt psychologists modified Law of
prägnanz and given laws which
hypothetically allow us to predict the
interpretation of sensation. These laws are
called "gestalt laws".
Figure-ground
Perceptual Organization
                            Reversible Figures

  Drawings that one can
  perceive in different
  ways by reversing
  figure and ground.
Gestalt Psychology
  School of thought
  rooted in the idea that
  the whole is different
  from the sum of its
  parts.
Camouflage
Importance of contour
Perceptual Organization
Gestalt Laws of Grouping
Proximity
  Seeing 3 pair of lines in A
Similarity
  Seeing columns of orange
  and red dots in B
Continuity
  Seeing lines that connect
  1 to 2 and 3 to 4 in C
Closure
  Seeing a horse in D
Gestalt Perceptual Psychology
 Laws of Perceptual Organization
 Law of Similarity
Gestalt Perceptual Psychology
 Laws of Perceptual Organization
 Law of Proximity (nearness)
General Perceptual Psychology
 Principles of Perceptual Organization
 The principle of common region
General Perceptual Psychology
 Principles of Perceptual Organization
 The principle of common region
General Perceptual Psychology
 Principles of Perceptual Organization
 The principle of connectedness
General Perceptual Psychology
 Principles of Perceptual Organization
 The principle of synchrony (objects that change
 together are grouped together)
General Perceptual Psychology
 Principles of Perceptual Organization
 Repetition Discrimination Task - groupings influence
 perception and speed of search:
Perceptual Segregation
  Figure-ground segregation-We are primed to see a
  figure in front of a background
  Symmetry and perception of figure and ground
Perceptual Segregation
  Figure-ground segregation-We are primed to see a
  figure in front of a background
  Area size and perception of figure and ground
Perceptual Segregation
  Figure-ground segregation-We are primed to see a
  figure in front of a background
  Orientation and perception of figure and ground
Perceptual Segregation
  Figure-ground segregation-We are primed to see a
  figure in front of a background
  Meaningfulness and perception of figure and ground
Pattern recognition
Pattern recognition and attention prepare
the raw sensory information for more
complex mental process.
Pattern recognition allows us to perceive a
form in a stimulus and attention is
responsible for our more extensive
processing of some information.
Pattern recognition is the identification of
complex arrangement of sensory stimuli.
In pattern recognition raw information is
organized and transformed by sensory
process and compared with information in
other memory storage.

Thus, pattern recognition involves realizing
that a particular pattern is seen before.
Bottom up processing (Data driven)

• emphasizes importance of stimulus in PR.
• Information coming from the stimulus is
  enough to recognize the pattern.
• Recognition process in initiated by the
  parts of the pattern which serves as the
  basis for the recognition of whole.
Top down processing (conceptually driven)


 Emphasizes that concept and high level of
 processing influence PR.
 Our knowledge about the world help us
 identifying patterns.
 The process of PR is initiated by a hypothesis
 about the whole leading to the identification
 of whole and the subsequent recognition of
 components.
Bottom up models of
     perception
How do we recognize patterns?
Do we identify an object because we have
first recognize it’s components or do we
recognize these part because we have first
identified the object?
The problem that, whether the recognition
process is initiated by the parts of the pattern
or whether it is initiated by a hypothesis
about the whole (hypothesis testing) is
called prasing paradox.
1 perceptual process
A: Template Matching Theory
 Templates are specific patterns that are
 stored in memory.
 Stimulus is compared with a set of
 templates.
 We recognize the stimulus as the template
 that matches most closely.
 Stimulus must fit the template precisely.
Problems of TMT

If a number of templates match or come close
   (not one)-
   We need further processing to sort out
   which template is most appropriate which
   will take much time than it actually takes.
   It does not explain how perception works.
   with the development of technology our
   experiences change thus, how and when
   templates are created?
How different patterns are recognized as
same despite the wide variation in the size,
shape, orientation etc. (e.g. recognizing
hand writing of different people).
It works for simple latter and simple objects.
B: Feature Analysis
 Feature analysis model assumes that instead of
 processing stimuli as whole units, we break them
 down into their components. We recognized those
 parts to infer what the whole represents.
 There is physiological mechanism in retina and in
 the cortex. These are called feature detectors.
 Some cells respond to boarders between light and
 dark called edge detectors.
 Movement detectors are called bug detectors.
 Horizontal and vertical line detectors are also found
 in the cortex.
1: Distinctive feature approach
 Discrimination among letters is made on the basis of
 small no of characteristics called distinctive features.

 We store a list of feature components for each letter.
 E.g. Q has a round closed shape and a diagonal line.

 Gibson (1969) demonstrated that people require long
 time to decide whether some letters are different
 from one another when the letter share large number
 of critical features.
For example, P and R are similar on a large
number of critical features; and G and M are
different from each other on a large number of
critical features.

Differentiation between G and M takes less time as
compared to differentiation between P and R.

In distinctive feature approach pattern recognition
involves detecting specific important parts while in
TMT emphasizes prototype and entire recognition
of entire shape.
Problems of distinctive feature approach
 Explain simple shape or features recognition such as
 letter recognition.
 It does not explain physical relationships. For
 example, T and L are similar but they are recognize
 distinctly on the basis of relationship. For example,
 T has a vertical line supports a horizontal line in the
 middle. Where L has the vertical line rests at the
 side of the horizontal line.
 It explains simple letter recognition but natural
 features, shapes are more complex. How can we
 recognize a horse?
2: The Computational Approach
        (David Marr (1982)
Images- Identification of object’s edges by
combining intensity of the image
Primal sketch- edges are organized into
abstract representation
2 ½ D sketch- primal sketch is converted
into 2 ½ D sketch (contours, shade, rough
depth)
3 D image- Describes shapes and their spatial
organization of the object.
Perceptual Organization
Identifying Objects

 Geons (geometric
 icons) are simple 3D
 component shapes.
 A limited number are
 stored in memory.
 Geons are combined to
 identify essential
 contours of objects.
Perceptual Constancies


 Size Constancy
   The tendency to view an object as constant
   in size despite changes in the size of the
   retinal image.
 Shape Constancy
   The tendency to see an object as keeping its
   form despite changes in orientation.
Perceptual Constancies
                              The Ames Room
A specially-built room that
makes people seem to
change size as they move
around in it
The room is not a
rectangle, as viewers
assume it is.
A single peephole prevents
using binocular depth cues.
Perceptual Constancies
             Shape Constancy




  Even though these images cast shadows of
  different shapes, they still are seen as round.
Perceptual Constancies
Size Constancy
 Tendency to view an object as constant in
 size despite changes in the size of the
 retinal image.




  http://www.psychologie.tu-dresden.de/i1/kaw/diverses%20Material/www.illusionworks.com/assets/images/constancy.jpg
Depth Perception:
Binocular Depth
      Cues
Binocular Cues
Depth cues that
require the use of
both eyes
Enables people to see
in three dimensions.
Retinal Disparity
A binocular depth cue resulting from
slightly different images produced by
the separation of the retinas in the left
and right eye
Is most effective when the item is quite
close to the person
Binocular Depth Cues: Finger Sausage
Retinal Disparity
Text example page 189
Autostereograms
Retinal Disparity Demo
1. Roll a piece of scrap paper into a tube shape.
2. Hold it to your right eye as if it were a telescope
3. Look through the tube focusing on an object
   on a blank wall in front of you.
4. Keeping both eyes open, hold your open left
   hand beside the tube…continue to focus on
   the object on the wall.
5. The images should fuse and ….
Convergence
A binocular depth cue related to the
tension in the eye muscles when the
eyes track inward to focus on objects
close to the viewer
The more tension in the eye muscle, the
closer the object is
Works best at close distances
Monocular Cues
Depth cues that require the use of only
one eye
Components of Monocular Cues
 Monocular depth cues include:
 1.relative size
 2.relative motion
 3.interposition
 4.relative height
 5.texture gradient
 6.relative clarity
 7.linear perspective
Monocular Depth Cues
           1. Relative Size
Using the perceived
size of a familiar
object to determine
depth
The larger the
object appears, the
closer the object is
to the viewer
Monocular Depth Cues
       2. Relative Motion
A person who is moving can determine
depth by focusing on a distant object.
Objects further away than the object of
focus will appear to move in the same
direction as the subject is moving.
Objects closer than the object of focus
will appear to move in the opposite
direction.
Relative Motion Illustration
Monocular Depth Cues
          3. Interposition
Method of
determining depth
by noting that
closer objects
partially obstruct
the more distant
objects
Also called
“overlap”
Monocular Depth Cues
              4. Relative Height
Method of
determining depth
by noting that
distant objects
appear higher in
your field of
vision than do
closer objects
Monocular Depth Cues
                 5. Texture Gradient
Method of determining depth by noting that distant
 objects have a smoother texture than nearby objects




       Can see individual blades of hay, but in the
       Distance, the hay seems to have a smoother
       Texture.
Monocular Depth Cues
             6. Relative Clarity
Method of
determining
depth by noting
that distant
objects are less
clear than
nearby objects
Tends to work Paris Street: A Rainy Day by Gustave
outdoors         Caillebotte
Monocular Depth Cues
          7. Linear Perspective
Method of
determining depth
by noting that
parallel lines appear
to converge in the
distance                As parallel lines become more
The lines appears to    distant from us, they appear to get
                        closer together - like the sides of
eventually merge on     the gray bit at left. Their
the horizon.            apparent closeness is therefore a
                        cue to their relative distance from
                        us.
Depth and Dimension
                 8.The Visual Cliff
Devised by Eleanor
Gibson and Richard Walk
to test depth perception in
infants and animals.
Provides visual illusion of
a cliff.
Caregiver stands across
the gap.
Babies are not afraid until
about the age they can
crawl.
Perceptual Set




  What is seen in the center figures depends on the
  order in which one looks at the figures:
     If scanned from the left, a man’s face is seen.
     If scanned from the right, a woman’s figure is
     seen.
Perceptual Set
                           Context Effects
 The same physical
 stimulus can be
 interpreted differently
 depending on
 perceptual set, e.g.,
 context effects.
 When is the middle
 character the letter B
 and when is it the
 number 13?
The World of Illusions
                        The Müller-Lyer Illusion

Illusion in which
the perceived
length of a line is
altered by the
position of other
lines that enclose it
The World of Illusions
The Ponzo Illusion
    Illusion in which the
    perceived line length
    is affected by linear
    perspective cues.
 Side lines seem to
 converge
 Top line seems farther
 away
   But the retinal images
   of the red lines are
   equal.
The Continuing Controversy

The ganzfield procedure
Researchers disagree about the reliability of
studies done to replicate the ganzfield test.
Visit www.randi.org/ for information about
the James Randi Educational Foundation’s
million-dollar paranormal challenge.

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1 perceptual process

  • 1. Cognition (mental activity or mental processes) Cognition (Latin: cognoscere, "to know" or "to recognize") refers to the acquisition, storage, transformation, and use of knowledge. Cognition can be natural or artificial, conscious or unconscious. It is a faculty of mental processes such as learning, memory, perception, thinking, problem solving, reasoning, decision making etc.
  • 2. Characteristics The cognitive processes are active, rather than passive The cognitive processes are remarkably efficient and accurate The cognitive processes Handle positive information better than negative information The cognitive processes are interrelated with one another, they do not operate in isolation many cognitive processes rely on both bottom- up and top-down processing
  • 3. Sensation and Perception Sensation The processes by which our sense organs receive information from the environment. Transduction The process by which physical energy is converted into sensory neural impulses. Perception The processes by which people select, organize, and interpret sensations.
  • 5. sensation Sensation is defined as: Irreducible elements from which perceptions are formed as experiences which are simpler and less meaningful than perceptions and uninfluenced by learning and other psychological processes such as emotion and motivation (Hebb, 1972; Scharf, 1975).
  • 6. Problems of perception No direct physical contact with the visual elements is required to appreciate there nature. How do we form the impressions of the quantitative and qualitative aspects of external objects? Does the real physical world actually exist independently of our experience? If so, how we can come to know its properties and how truth of that knowledge be determined?
  • 7. Problems… How percepts are constructed from the interaction of physical energy (light) and the perceiving organism. Proximal and distal stimuli are different but our perceptions are generally accurate or veridical enough to adjust ourselves in the environment. Some times percept have properties considerably different form proximal stimulus.
  • 8. Components of perception Distal stimulus Distal stimulus refers to a physical aspect of the external environment, or the physical energy which comes from the eternal source. For example, object in the external environment such as, table, fan etc. Proximal stimulus It refers to the physical energy coming from the external source strikes on the sensory receptors.
  • 9. Components… Input and output Input refers to the sensation of stimulus and output refers to behavior made in response to the input. Percept Out come of perception is known as percept. Recognizing an object as flower would be an example of percept.
  • 10. Difference between proximal and distal stimulus Much of the light coming form distal source is scattered by molecules and lost before it reaches the receptors of the eye. Resulting proximal image is much smaller, inverted relative to the distal stimulus Proximal stimulus is partly under the control of observer’s head and eye movements. Information in the form of electromagnetic energy is changed in the neural impulses (transduction).
  • 11. Defining perception According to Morgan and King, “perception is the way the world look (sounds, feels, tastes and smells too)”. According to Zigher (1985), perception refers to the interpretation of sensory information, as a constructive and creative process which endows sensory experience with meaning.
  • 12. Defining… Perception is a process by which individuals organize and interpret their sensory impressions in order give meaning to their environment for making better adjustment with it. Perception is a process by which we recognize and interpret or give meaning to raw material provided by sensory system with the help of other psychological processes such as, learning, memory, emotions and motivation.
  • 13. Defining… Perception is the process of creating an internal representation of the out side world (internal representation is a joint product of bottom up and top-down processing). Perception is the interpretation of the information provided by sensory system.
  • 14. Perception is active, selective and relatively more automatic higher mental process through which we experience or interpret our immediate surrounding.
  • 15. Properties of perception Perception is interpretation of physical energy or giving meaning to it. In perception, registered stimuli by the senses are gathered and interpreted with the help of previous knowledge. Perception combines aspect of both the outside world (the stimulus) and inner world (previous knowledge).
  • 16. Properties … Perception is relatively more automatic process, required less effort than other cognitive tasks, such as problem solving of decision making. Perception is influenced by other psychological processes such as motivation and emotion. Perception is an active mental process involves both top-down and bottom-up processing.
  • 17. Concepts in perception Physical- external or internal stimulus such as wave length, intensity etc. Physiological- stimulation of sensory system: neural activity- excitation- inhibition; sensory modality: transduction Behavior Subjective experience
  • 18. Perception Perceptual Organization Perceptual Constancies Depth and Dimension Perceptual Set The World of Illusions
  • 19. Approaches to perception Structuralism Wilhelm Wundt and Edward Bradford Titchner (1867-1927) Structuralisms emphasized on the study of the structure of perception. Its goal was to uncover the simplest, most basic elements of conscious experience (bottom-up processing).
  • 20. Constructivist Approach Emphasized on the active nature of perceptual process. Influenced by empiricism. Proposed that the percept is more than the information coming form stimulus. Some constructive processes occur within the observer. These are mediating processes between physical world and its perception. Our perception is a mental construction based on our cognitive strategies, past experiences, biases, expectations, motives, attention, and other personal characteristics
  • 21. Direct perception approach (James J. Gibson, 1904-1979) Stimulus contains important information necessary for perception Past experiences are not important Perception depends on the characteristics of stimuli (subjective variables are not important) It is also known as ecological approach because it focuses on the adaptive link between the perceiving organism to its physical environment.
  • 22. Computational Approach (David Marr, 1945-1980) Involves mathematically oriented analysis of certain aspects of visual perception derived form computer simulation and AI. Accepts Gibson’s basic idea of direct perception but also proposes that perception of characteristics such as lines, edges, borders, contours, motion, and other discontinuity.
  • 23. Beliefs of the information-processing approach Information is processed in stages Information is processed serially The nature of information changes stage to stage Information processing is affected by several factors (noise) It uses both bottom-up and top-down processing It is a mediating process between input and output
  • 24. Gestalt approach (German: Gestalt - "shape" or "figure") Berlin School Kurt Koffka, Max Wertheimer, and Wolfgang Köhler (students of Carl Stumpf) are the founder of this school. The 'Gestalt' or 'whole form' approach sought to define principles of perception -- seemingly innate mental laws which determined the way in which objects were perceived.
  • 25. Gestalt: Basic idea Operational principle of the brain is holistic, parallel, and analog, with self-organizing tendencies “The whole is greater than the sum of the parts" Opposed to structuralism and Wundt Gestalt effect refers to the form-forming capability of our senses particularly visual sense.
  • 26. Figure and ground Properties of figure ground Figures hold more memorable association than the ground. Figures are seen as being in front of the ground. The ground is seen as uniformed material and seems to extend behind the figure. The contour separating the figure from the ground appears to belong to the figure. Compared to ground, perception of figure is effortless
  • 27. Field forces Cohesive forces Restraining forces ∑ C = ∑ R = no perception (Ganzfeld) ∑ C > ∑ R = perception ∑ C < ∑ R = unclear or unstable perception
  • 28. Laws of pragnanz The fundamental principle of gestalt perception is the law of prägnanz (German for pithiness). The physiological organization will always be good. Good refers to the simplest and most stable. We tend to order our experience in a manner that is regular, orderly, symmetric, and simple.
  • 29. Gestalt laws of perceptual organization Gestalt psychologists modified Law of prägnanz and given laws which hypothetically allow us to predict the interpretation of sensation. These laws are called "gestalt laws".
  • 31. Perceptual Organization Reversible Figures Drawings that one can perceive in different ways by reversing figure and ground. Gestalt Psychology School of thought rooted in the idea that the whole is different from the sum of its parts.
  • 33. Perceptual Organization Gestalt Laws of Grouping Proximity Seeing 3 pair of lines in A Similarity Seeing columns of orange and red dots in B Continuity Seeing lines that connect 1 to 2 and 3 to 4 in C Closure Seeing a horse in D
  • 34. Gestalt Perceptual Psychology Laws of Perceptual Organization Law of Similarity
  • 35. Gestalt Perceptual Psychology Laws of Perceptual Organization Law of Proximity (nearness)
  • 36. General Perceptual Psychology Principles of Perceptual Organization The principle of common region
  • 37. General Perceptual Psychology Principles of Perceptual Organization The principle of common region
  • 38. General Perceptual Psychology Principles of Perceptual Organization The principle of connectedness
  • 39. General Perceptual Psychology Principles of Perceptual Organization The principle of synchrony (objects that change together are grouped together)
  • 40. General Perceptual Psychology Principles of Perceptual Organization Repetition Discrimination Task - groupings influence perception and speed of search:
  • 41. Perceptual Segregation Figure-ground segregation-We are primed to see a figure in front of a background Symmetry and perception of figure and ground
  • 42. Perceptual Segregation Figure-ground segregation-We are primed to see a figure in front of a background Area size and perception of figure and ground
  • 43. Perceptual Segregation Figure-ground segregation-We are primed to see a figure in front of a background Orientation and perception of figure and ground
  • 44. Perceptual Segregation Figure-ground segregation-We are primed to see a figure in front of a background Meaningfulness and perception of figure and ground
  • 45. Pattern recognition Pattern recognition and attention prepare the raw sensory information for more complex mental process. Pattern recognition allows us to perceive a form in a stimulus and attention is responsible for our more extensive processing of some information. Pattern recognition is the identification of complex arrangement of sensory stimuli.
  • 46. In pattern recognition raw information is organized and transformed by sensory process and compared with information in other memory storage. Thus, pattern recognition involves realizing that a particular pattern is seen before.
  • 47. Bottom up processing (Data driven) • emphasizes importance of stimulus in PR. • Information coming from the stimulus is enough to recognize the pattern. • Recognition process in initiated by the parts of the pattern which serves as the basis for the recognition of whole.
  • 48. Top down processing (conceptually driven) Emphasizes that concept and high level of processing influence PR. Our knowledge about the world help us identifying patterns. The process of PR is initiated by a hypothesis about the whole leading to the identification of whole and the subsequent recognition of components.
  • 49. Bottom up models of perception
  • 50. How do we recognize patterns? Do we identify an object because we have first recognize it’s components or do we recognize these part because we have first identified the object? The problem that, whether the recognition process is initiated by the parts of the pattern or whether it is initiated by a hypothesis about the whole (hypothesis testing) is called prasing paradox.
  • 52. A: Template Matching Theory Templates are specific patterns that are stored in memory. Stimulus is compared with a set of templates. We recognize the stimulus as the template that matches most closely. Stimulus must fit the template precisely.
  • 53. Problems of TMT If a number of templates match or come close (not one)- We need further processing to sort out which template is most appropriate which will take much time than it actually takes. It does not explain how perception works. with the development of technology our experiences change thus, how and when templates are created?
  • 54. How different patterns are recognized as same despite the wide variation in the size, shape, orientation etc. (e.g. recognizing hand writing of different people). It works for simple latter and simple objects.
  • 55. B: Feature Analysis Feature analysis model assumes that instead of processing stimuli as whole units, we break them down into their components. We recognized those parts to infer what the whole represents. There is physiological mechanism in retina and in the cortex. These are called feature detectors. Some cells respond to boarders between light and dark called edge detectors. Movement detectors are called bug detectors. Horizontal and vertical line detectors are also found in the cortex.
  • 56. 1: Distinctive feature approach Discrimination among letters is made on the basis of small no of characteristics called distinctive features. We store a list of feature components for each letter. E.g. Q has a round closed shape and a diagonal line. Gibson (1969) demonstrated that people require long time to decide whether some letters are different from one another when the letter share large number of critical features.
  • 57. For example, P and R are similar on a large number of critical features; and G and M are different from each other on a large number of critical features. Differentiation between G and M takes less time as compared to differentiation between P and R. In distinctive feature approach pattern recognition involves detecting specific important parts while in TMT emphasizes prototype and entire recognition of entire shape.
  • 58. Problems of distinctive feature approach Explain simple shape or features recognition such as letter recognition. It does not explain physical relationships. For example, T and L are similar but they are recognize distinctly on the basis of relationship. For example, T has a vertical line supports a horizontal line in the middle. Where L has the vertical line rests at the side of the horizontal line. It explains simple letter recognition but natural features, shapes are more complex. How can we recognize a horse?
  • 59. 2: The Computational Approach (David Marr (1982) Images- Identification of object’s edges by combining intensity of the image Primal sketch- edges are organized into abstract representation 2 ½ D sketch- primal sketch is converted into 2 ½ D sketch (contours, shade, rough depth) 3 D image- Describes shapes and their spatial organization of the object.
  • 60. Perceptual Organization Identifying Objects Geons (geometric icons) are simple 3D component shapes. A limited number are stored in memory. Geons are combined to identify essential contours of objects.
  • 61. Perceptual Constancies Size Constancy The tendency to view an object as constant in size despite changes in the size of the retinal image. Shape Constancy The tendency to see an object as keeping its form despite changes in orientation.
  • 62. Perceptual Constancies The Ames Room A specially-built room that makes people seem to change size as they move around in it The room is not a rectangle, as viewers assume it is. A single peephole prevents using binocular depth cues.
  • 63. Perceptual Constancies Shape Constancy Even though these images cast shadows of different shapes, they still are seen as round.
  • 64. Perceptual Constancies Size Constancy Tendency to view an object as constant in size despite changes in the size of the retinal image. http://www.psychologie.tu-dresden.de/i1/kaw/diverses%20Material/www.illusionworks.com/assets/images/constancy.jpg
  • 66. Binocular Cues Depth cues that require the use of both eyes Enables people to see in three dimensions.
  • 67. Retinal Disparity A binocular depth cue resulting from slightly different images produced by the separation of the retinas in the left and right eye Is most effective when the item is quite close to the person
  • 68. Binocular Depth Cues: Finger Sausage
  • 71. Retinal Disparity Demo 1. Roll a piece of scrap paper into a tube shape. 2. Hold it to your right eye as if it were a telescope 3. Look through the tube focusing on an object on a blank wall in front of you. 4. Keeping both eyes open, hold your open left hand beside the tube…continue to focus on the object on the wall. 5. The images should fuse and ….
  • 72. Convergence A binocular depth cue related to the tension in the eye muscles when the eyes track inward to focus on objects close to the viewer The more tension in the eye muscle, the closer the object is Works best at close distances
  • 73. Monocular Cues Depth cues that require the use of only one eye
  • 74. Components of Monocular Cues Monocular depth cues include: 1.relative size 2.relative motion 3.interposition 4.relative height 5.texture gradient 6.relative clarity 7.linear perspective
  • 75. Monocular Depth Cues 1. Relative Size Using the perceived size of a familiar object to determine depth The larger the object appears, the closer the object is to the viewer
  • 76. Monocular Depth Cues 2. Relative Motion A person who is moving can determine depth by focusing on a distant object. Objects further away than the object of focus will appear to move in the same direction as the subject is moving. Objects closer than the object of focus will appear to move in the opposite direction.
  • 78. Monocular Depth Cues 3. Interposition Method of determining depth by noting that closer objects partially obstruct the more distant objects Also called “overlap”
  • 79. Monocular Depth Cues 4. Relative Height Method of determining depth by noting that distant objects appear higher in your field of vision than do closer objects
  • 80. Monocular Depth Cues 5. Texture Gradient Method of determining depth by noting that distant objects have a smoother texture than nearby objects Can see individual blades of hay, but in the Distance, the hay seems to have a smoother Texture.
  • 81. Monocular Depth Cues 6. Relative Clarity Method of determining depth by noting that distant objects are less clear than nearby objects Tends to work Paris Street: A Rainy Day by Gustave outdoors Caillebotte
  • 82. Monocular Depth Cues 7. Linear Perspective Method of determining depth by noting that parallel lines appear to converge in the distance As parallel lines become more The lines appears to distant from us, they appear to get closer together - like the sides of eventually merge on the gray bit at left. Their the horizon. apparent closeness is therefore a cue to their relative distance from us.
  • 83. Depth and Dimension 8.The Visual Cliff Devised by Eleanor Gibson and Richard Walk to test depth perception in infants and animals. Provides visual illusion of a cliff. Caregiver stands across the gap. Babies are not afraid until about the age they can crawl.
  • 84. Perceptual Set What is seen in the center figures depends on the order in which one looks at the figures: If scanned from the left, a man’s face is seen. If scanned from the right, a woman’s figure is seen.
  • 85. Perceptual Set Context Effects The same physical stimulus can be interpreted differently depending on perceptual set, e.g., context effects. When is the middle character the letter B and when is it the number 13?
  • 86. The World of Illusions The Müller-Lyer Illusion Illusion in which the perceived length of a line is altered by the position of other lines that enclose it
  • 87. The World of Illusions The Ponzo Illusion Illusion in which the perceived line length is affected by linear perspective cues. Side lines seem to converge Top line seems farther away But the retinal images of the red lines are equal.
  • 88. The Continuing Controversy The ganzfield procedure Researchers disagree about the reliability of studies done to replicate the ganzfield test. Visit www.randi.org/ for information about the James Randi Educational Foundation’s million-dollar paranormal challenge.

Editor's Notes

  1. Sensation &amp; Perception 10/10/12 ©2001 Prentice Hall
  2. Sensation &amp; Perception 10/10/12 ©2001 Prentice Hall Figure 3.2 from: Kassin, S. (2001). Psychology , third edition. Upper Saddle River, NJ: Prentice Hall.
  3. Sensation &amp; Perception 10/10/12 ©2001 Prentice Hall Section outline
  4. Sensation &amp; Perception 10/10/12 ©2001 Prentice Hall Figure 3.20 (lady/girl) and 3.21 (rabbit/duck) from: Kassin, S. (2001). Psychology , third edition. Upper Saddle River, NJ: Prentice Hall. Quote from: Shephard, R. N. (1990). Mind Sights . New York: W. H. Freeman.
  5. Sensation &amp; Perception 10/10/12 ©2001 Prentice Hall Figure 3.23 from: Kassin, S. (2001). Psychology , third edition. Upper Saddle River, NJ: Prentice Hall.
  6. Sensation &amp; Perception 10/10/12 ©2001 Prentice Hall Figure 3.25 from: Kassin, S. (2001). Psychology , third edition. Upper Saddle River, NJ: Prentice Hall. Source: Biederman, I. (1987). Recognition-by-components: A theory of human image understanding. Psychological Review, 94 , 115-147.
  7. Sensation &amp; Perception 10/10/12 ©2001 Prentice Hall Figure 3.25 from: Kassin, S. (2001). Psychology , third edition. Upper Saddle River, NJ: Prentice Hall.
  8. Sensation &amp; Perception 10/10/12 ©2001 Prentice Hall Figure 3.26 from: Kassin, S. (2001). Psychology , third edition. Upper Saddle River, NJ: Prentice Hall.
  9. Perceptual constancies – perception of entire object does not change, even though some of the sensory items have changed Size Constancy Tendency to view an object as constant in size despite changes in the size of the retinal image. Wundt had no way to explain why this happened either, just like the phi phen.
  10. Sensation &amp; Perception 10/10/12 ©2001 Prentice Hall Figure 3.27 from: Kassin, S. (2001). Psychology , third edition. Upper Saddle River, NJ: Prentice Hall.
  11. Sensation &amp; Perception 10/10/12 ©2001 Prentice Hall Figure 3.28 from: Kassin, S. (2001). Psychology , third edition. Upper Saddle River, NJ: Prentice Hall.
  12. Sensation &amp; Perception 10/10/12 ©2001 Prentice Hall Figure 3.29 from: Kassin, S. (2001). Psychology , third edition. Upper Saddle River, NJ: Prentice Hall.
  13. Sensation &amp; Perception 10/10/12 ©2001 Prentice Hall Figure 3.32 from: Kassin, S. (2001). Psychology , third edition. Upper Saddle River, NJ: Prentice Hall.