slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Perception PowerPoint Presentation
Download Presentation
Perception

Loading in 2 Seconds...

play fullscreen
1 / 72

Perception - PowerPoint PPT Presentation


  • 196 Views
  • Uploaded on

Perception. What you want to remember. Perception is more than photons and pressure. Perception is divided from cognition/emotion but they are often intertwined. Perception follows laws and heuristics. Sensation. Sensation - the registration of physical stimuli

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Perception' - shelly


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide2

What you want to remember

  • Perception is more than photons and pressure.
  • Perception is divided from cognition/emotion but they are often intertwined.
  • Perception follows laws and heuristics.
slide3

Sensation

  • Sensation - the registration of physical stimuli
    • Hearing - anatomy and function of the ear
    • Vision - anatomy and function of the eye
slide4

Sensation

  • What is the purpose of sensory processing?
    • To transform physical stimuli in the environment into neural signals in the brain
    • Example (Hearing): Sound waves are transformed into vibrations in the ear, and the strength of those vibrations are coded by sensory neurons
slide5

Some Questions of Interest

  • How can we perceive an object like a chair as having a stable form, given that the image of the chair on our retina changes as we look at it from different directions?
slide6

Some Questions of Interest

  • What are two fundamental approaches to explaining perception?
  • What happens when people with normal visual sensations cannot perceive visual stimuli?
slide7

Perception Is…

  • The process of recognizing, organizing, and interpreting information
  • How do you recognize these items?
slide8

Basic Concepts (Gibson)

  • Distal object
    • Grandma’s face
  • Informational medium
    • Reflected light from Grandma’s face
  • Proximal stimulation
    • Photon absorption in the rod and cone cells of the retina
  • Perceptual object
    • Grandma’s face
slide9

Perceptual Basics

  • Sensory adaptation
    • Occurs when sensory receptors change their sensitivity to the stimulus
    • Constant stimulation leads to lower sensitivity
  • Our senses respond to change
  • Perceptual training
slide10

Perceptual Illusions

  • Sometimes we cannot perceive what does exist
  • Sometimes we perceive things that do not exist
slide11

Perceptual Illusions

  • Sometimes we perceive what cannot be there
slide13

Figure 7.4

Figure 7.4 The basilar membrane of the human cochlea. High-frequency sounds produce their maximum displacement near the base. Low-frequency sounds produce their maximum displacement near the apex.

slide14

Corresponds to apex of cochlea

Corresponds to base of cochlea

Primary auditory cortex

Secondary auditory cortex

Auditory Cortex

  • Tonotopic organization in superior temporal lobe
slide15

Typical human range about 20 - 20 kHz

Audiograms for various species

slide16

Our Visual System

  • Light travels through the eye and focuses on the retina
    • Electromagnetic light energy is converted into neural electrochemical impulses
slide17

Our Visual System

  • Three main layers of neural tissue in retina
    • Ganglion cells
    • Amacrine cells, horizontal cells, bipolar cells
    • Photoreceptors
      • Rods and cones
slide18

Visual Pathways in the Brain

  • What/where hypothesis
    • One path for identifying
      • Temporal lobe lesions in monkeys
        • Can indicate where but not what
    • Another for spatially locating
      • Parietal lobe lesions in monkeys
        • Can indicate what but not where
slide19

Theories of Perception

  • Bottom-up theories
    • Parts are identified, put together, and then recognition occurs
  • Top-down theories
    • People actively construct perceptions using information based on expectations
slide20

0

Bottom-Up Processing Theories

  • Direct perception
  • Template theories
  • Feature-matching theories
  • Recognition-by-components theory
slide21

0

Template Theories

  • Basics of template theories
    • Multiple templates are held in memory
    • To recognize the incoming stimuli, you compare to templates in memory until a match is found

Search memory for a match

See stimuli

slide22

0

Template Theories

  • Weakness of theory
    • Problem of imperfect matches
    • Cannot account for the flexibility of pattern recognition system

Search for match in memory

See stimuli

No perfect match in memory

slide23

0

Feature-Matching Theories

  • Recognize objects on the basis of a small number of characteristics (features)
    • Detect specific elements and assemble them into more complex forms
    • Brain cells that respond to specific features such as lines and angles are referred to as “feature detectors”
slide24

Pandemonium Model

  • Four kinds of demons
    • Image demons
    • Feature demons
    • Cognitive demons
    • Decision demons
slide25

0

Physiological Evidence for Features

  • Hubel & Wiesel (1979)
    • Simple cells detect bars or edges of particular orientation in particular location
    • Complex cells detect bars or edges of particular orientation, exact location abstracted
    • Hypercomplex cells detect particular colors (simple and complex cells), bars, or edges of particular length or moving in a particular direction
slide26

0

Recognition-by-Components (RBC) Theory

  • Biederman (1987)
    • Describes how 3D images are identified
    • Breaks objects down into geons
    • Objects are identified by geons, relationship between them
slide27

Gibson’s Theory of Direct Perception (Ecological psych)

  • The information in our sensory receptors is all we need to perceive anything
    • Do not need the aid of complex thought processes to explain perception
slide28

Gibson’s Theory of Direct Perception (Ecological psych)

  • Use texture gradients as cues for depth and distance
    • Allows us to perceive directly the relative proximity or distance of objects
slide29

0

Top-Down Processing (Constructive Approach)

  • Perception is not automatic from raw stimuli
  • Processing is needed to build perception
  • Top-down processing occurs quickly and involves making inferences, guessing from experience, and basing one perception on another
slide30

0

Evidence for Top-Down Processing

  • Context effects
slide31

Configural-Superiority Effect

  • Objects presented in context are easier to recognize than objects presented alone
  • Task: Spot the different stimuli, press button
slide32

Configural-Superiority Effect

Target

Composite

Measure reaction time

Target alone = 1884 Composite = 749

Target spotted faster in a context!

slide33

Which Approach Is Right?

  • Top-down or bottom-up
    • Perhaps a bit of both
slide34

Beginning of Gestalt psychology

  • 1910 – Max Wertheimer on vacation noticed that distal objects seemed to move with the train; nearby objects went past. Why?
  • Study of apparent motion – why stationary objects appear to move

34

slide35

Apparent motion

  • Phi phenomenon – flashing a vertical light that is followed 50-60 msec later by a horizontal light produces the appearance of movement. The light appears to move from vertical to horizontal
  • Movement only perceived if delay was 50 – 60 msec
  • The perceptual experience had properties the individual components did not
  • 1st Gestalt paper presented in 1912

35

slide36

Basic premise of Gestalt psychology

  • Humans are not passive receivers of sensory information. Our perceptions are active, lively, and organized
  • We actively organize perceptions into coherent wholes – today the process is referred to as top-down or conceptually driven processing

36

slide37

Scientific Method

  • Gestalt perspectives on scientific method reflect their acceptance of field physics as a model for psychology.
    • They emphasized the physical environment.
    • They used experience to guide analysis in psychology.
    • They started research with phenomenological investigation.
    • They accepted a broad range of methods in psychology.
slide38

Mind and Brain

  • Gestalt perspectives on mind and brain reject reductionistic and linear models of mind.
    • Köhler argued for models of mind based in natural systems.
    • He used models of mind based in the brain.
    • He described models in terms of free dynamics.
    • Köhler advocated isomorphism (ex. psychophysical isomorphism).
      • There is a structural correspondence between experience and underlying brain processes.
slide39

Key terms in gestalt psychology: Geographical versus behavioral environment

  • Geographical environment – the physical world
  • Behavioral environment – our interpretation of the physical world
  • Our interpretation or organization can produce a behavioral world that is very different from the physical world
  • Illusions, dreaming, fantasies

39

slide40

Gestalt’s View of Perception

  • Basic tenet
    • “The whole is more than a sum of its parts”
  • Law of Prägnanz
    • Individuals organize their experience in as simple, concise, symmetrical, and complete manner as possible
slide43

Perception is not just detection

  • Perception is not just about detecting color or shape.
  • Perception is about organizing visual information.
  • How do we organize visual information?
slide48

Gestalt’s Principles of Visual Perception

  • Figure-ground
    • Organize perceptions by distinguishing between a figure and a background
  • Proximity
    • Elements tend to be grouped together according to their nearness
  • Similarity
    • Items similar in some respect tend to be grouped together
slide49

The figure represents “some thing.”

The contours belong to the figure rather than to the ground.

slide50

Which one if the figure and which is the ground?

This is easy.

The figure tends to have solid and continuous surface.

gestalt s principles of visual perception
Gestalt’s Principles of Visual Perception
  • Continuity
    • Based on smooth continuity, which is preferred to abrupt changes of direction
  • Closure
    • Items are grouped together if they tend to complete a figure
  • Symmetry
    • Prefer to perceive objects as mirror images

B

A

D

C

slide53

Rules for Linking Contours

  • Good continuation: group elements to form smoothly continuing lines
slide55

Meaning in the Edges

  • Non-accidental features provide clues to object structure
slide56

Is the Whole Seen Before the Parts?

  • Global superiority effect (Navon, 1977)
slide57

Complex listening: several concurrent sound sources

  • Auditory scene analysis
  • “cocktail-party effect”
slide62

Depth Perception

  • The ability to see the world in three dimensions and detect distance
    • Vision only has a two-dimensional view
    • We must interpret the information given to perceive depth
    • We take flat images and create a three-dimensional view
    • Optical illusions demonstrate that this interpretation does not always have to be correct
slide63

Monocular Depth Cues

  • Texture gradients
    • Grain of item
  • Relative size
    • Bigger is closer
  • Interposition
    • Closer are in front of other objects
slide64

Monocular Depth Cues

  • Linear perspective
    • Parallel lines converge in distance
  • Aerial perspective
    • Images seem blurry farther away
  • Motion parallax
    • Objects get smaller at decreasing speed in distance
slide65

Binocular Depth Cues

  • Binocular convergence
    • Eyes turn inward as object moves toward you; brain uses this information to judge distance
  • Binocular disparity
    • Each eye views a slightly different angle of an object; brain uses this to create a 3D image
slide66

Agnosias, Ataxias, & Cognition

  • Demonstrate the modularity of cognition
  • Help us to understand what brain locations are associated with different types of higher-level processing
  • Provide us with a model of how normal processing must work
slide67

Deficits in Perception

  • Disruption of the “what” pathway
        • Inability to recognize and identify objects or people, despite having knowledge of the characteristics of the objects or people
  • Disruption of the “how” pathway
      • Cannot use vision to guide movement
      • Unable to reach for items
slide68

Fusiform Gyrus in Temporal Lobe

  • Implicated in pattern recognition
  • Studies illustrate it is active in facial recognition
  • However, also active if high expertise in any item (birds, cars) recognition
    • Expert individuation hypothesis
slide69

Evidence for Separate Systems

  • Prosopagnosia
    • Inability to recognize faces after brain damage
    • Ability to recognize objects is intact
  • Associative agnosia
    • Difficulty with recognizing objects
    • Can recognize faces
slide70

Psychophysics

  • the measurement of sensory experiences
  • Webers Law
      • Δφ = cφφ = Stimuli
  • Fechners Law
    • Ψ = log φΨ = Sensation magnitude
slide71

Perception or Attention

  • Movement patterns / reflexes
  • What cannot be unseen / heard
  • Pop-out effect
  • Change blindness
slide72

What you want to remember

  • Perception is more than photons and pressure.
  • Perception is divided from cognition/emotion but they are often intertwined.
  • Perception follows laws and heuristics.