PSYCHOLOGY 11002 General Psychology

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PSYCHOLOGY 110-02General Psychology

• University of Southern Mississippi
• Department of Psychology
• Dr. David J. Echevarria, PhD
• Spring 2008
• david.echevarria_at_usm.edu
• www.usm.edu/neurolab

Chapter 4 Sensation and Perception
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Chapter 4 Sensation and Perception
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What is real?
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What is real???

• Being or occurring in fact or actuality having
  verifiable existence real objects a real
  illness.
• True and actual not imaginary, alleged, or
  ideal real people, not ghosts a film based on
  real life.
• Of or founded on practical matters and concerns
  a recent graduate experiencing the real world for
  the first time.

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What is real???

• Morpheus  "What is real?  How do you define
  real?  If you're talking about your senses, what
  you feel, taste, smell, or see, then all you're
  talking about are electrical signals interpreted
  by your brain."

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What is real???

• Morpheus  "What is real?  How do you define
  real?  If you're talking about your senses, what
  you feel, taste, smell, or see, then all you're
  talking about are electrical signals interpreted
  by your brain."

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Reality

• Information from the external real world comes
  into 1 or more of 5 sensory modalities
• This information interacts with receptors that
  have evolved for a purpose
• Transduction occurs and you now have an internal
  representation of the external world
• electrical signals interpreted by your brain

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• http//www.johnsadowski.com/big_spanish_castle.php

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Sensation and Perception The Distinction

• Sensation stimulation of sense organs
• Perception selection, organization, and
  interpretation of sensory input
• Psychophysics the study of how physical stimuli
  are translated into psychological experience

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Figure 4.1 The distinction between sensation and
perception
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Psychophysics Basic Concepts

• Sensation begins with a detectable stimulus
• Fechner the concept of the threshold
• Absolute threshold detected 50 of the time
• Just noticeable difference (JND) smallest
  difference detectable
• Webers law size of JND proportional to size of
  initial stimulus

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Figure 4.2 The absolute threshold
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Psychophysics Concepts and Issues

• Signal-Detection Theory Sensory processes
  decision processes
• Subliminal Perception Existence vs. practical
  effects
• Sensory Adaptation Decline in sensitivity

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Figure 4.3 Signal-detection theory
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Vision The Stimulus

• Light electromagnetic radiation
• Amplitude perception of brightness
• Wavelength perception of color
• Purity mix of wavelengths
• perception of saturation, or richness of colors.

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Figure 4.5 Light, the physical stimulus for
vision
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Figure 4.7 The human eye
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The EyeConverting Light into Neural Impulses

• The eye housing and channeling
• Components
• Cornea where light enters the eye
• Lens focuses the light rays on the retina
• Iris colored ring of muscle, constricts or
  dilates via amount of light
• Pupil regulates amount of light

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The Retina An Extension of the CNS

• Retina absorbs light, processes images
• Optic disk optic nerve connection/blind spot
• Receptor cells
• Rods black and white/low light vision
• Cones color and daylight vision
• Adaptation becoming more or less sensitive to
  light as needed
• Information processing
• Receptive fields
• Lateral antagonism

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Figure 4.8 Nearsightedness and farsightedness
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What is Sensation and what is Perception?
Todays minute quiz
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Figure 4.9 The retina
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Figure 4.13 Visual pathways through the brain
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The Retina and the BrainVisual Information
Processing

• Light ? rods and cones ? neural signals ? bipolar
  cells ? ganglion cells ? optic nerve ? optic
  chiasm ? opposite half brain
• Main pathway lateral geniculate nucleus
  (thalamus) ? primary visual cortex (occipital
  lobe)
• magnocellular where
• parvocellular what
• Second pathway superior colliculus ? thalamus ?
  primary visual cortex

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Figure 4.15 The what and where pathways from the
primary visual cortex
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Hubel and WieselFeature Detectors and the Nobel
Prize

• Early 1960s Hubel and Wiesel
• Microelectrode recording of axons in primary
  visual cortex of animals
• Discovered feature detectors neurons that
  respond selectively to lines, edges, etc.
• Groundbreaking research Nobel Prize in 1981
• Later research cells specific to faces in the
  temporal lobes of monkeys and humans

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Basics of Color Vision

• Wavelength determines color
• Longer red / shorter violet
• Amplitude determines brightness
• Purity determines saturation

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Figure 4.17 Additive versus subtractive color
mixing
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Theories of Color Vision

• Trichromatic theory - Young and Helmholtz
• Receptors for red, green, blue color mixing
• Opponent Process theory Hering
• 3 pairs of antagonistic colors
• red/green, blue/yellow, black/white
• Current perspective both theories necessary

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Figure 4.18 The color circle and complementary
colors
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Perceiving Forms, Patterns, and Objects

• Reversible figures
• Perceptual sets
• Inattentional blindness
• Feature detection theory - bottom-up processing
• Form perception - top-down processing
• Subjective contours
• Gestalt psychologists the whole is more than
  the sum of its parts
• Reversible figures and perceptual sets
  demonstrate that the same visual stimulus can
  result in very different perceptions

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Figure 4.22 Feature analysis in form perception
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Figure 4.23 Bottom-up versus top-down processing
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Figure 4.24 Subjective contours
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Principles of Perception

• Gestalt principles of form perception
• figure-ground, proximity, similarity, continuity,
  closure, and simplicity
• Recent research
• Distal (stimuli outside the body) vs. proximal
  (stimulus energies impinging on sensory
  receptors) stimuli
• Perceptual hypotheses
• Context

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Figure 4.25 The principle of figure and ground
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Figure 4.26 Gestalt principles of perceptual
organization
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Figure 4.27 Distal and proximal stimuli
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Figure 4.28 A famous reversible figure
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Figure 4.29 The Necker cube
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Figure 4.30 Context effects
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Depth and Distance Perception

• Binocular cues clues from both eyes together
• retinal disparity
• convergence
• Monocular cues clues from a single eye
• motion parallax
• accommodation
• pictorial depth cues

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Stability in the Perceptual WorldPerceptual
Constancies

• Perceptual constancies stable perceptions amid
  changing stimuli
• Size
• Shape
• Brightness
• Hue
• Location in space

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Optical IllusionsThe Power of Misleading Cues

• Optical Illusions - discrepancy between visual
  appearance and physical reality
• Famous optical illusions Muller-Lyer Illusion,
  Ponzo Illusion, Poggendorf Illusion, Upside-Down
  T Illusion, Zollner Illusion, the Ames Room, and
  Impossible Figures
• Cultural differences Perceptual hypotheses at
  work

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The Ames Room
Mac OS X
Windows
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Figure 4.37 The Muller-Lyer illusion
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Figure 4.38 Explaining the Muller-Lyer Illusion
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Figure 4.39 Four geometric illusions
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Figure 4.41 The Ames room
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Figure 4.42 Three classic impossible figures
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Hearing The Auditory System

• Stimulus sound waves (vibrations of molecules
  traveling in air)
• Amplitude (loudness)
• Wavelength (pitch)
• Purity (timbre)
• Wavelength described in terms of frequency
  measured in cycles per second (Hz)
• Frequency increase pitch increase

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Figure 4.44 Sound, the physical stimulus for
hearing
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The Ear Three Divisions

• External ear (pinna) collects sound
• Middle ear the ossicles (hammer, anvil, stirrup)
• Inner ear the cochlea
• a fluid-filled, coiled tunnel
• contains the hair cells, the auditory receptors
• lined up on the basilar membrane

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Figure 4.46 The human ear
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Figure 4.47 The basilar membrane
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The Auditory Pathway

• Sound waves vibrate bones of the middle ear
• Stirrup hits against the oval window of cochlea
• Sets the fluid inside in motion
• Hair cells are stimulated with the movement of
  the basilar membrane
• Physical stimulation converted into neural
  impulses
• Sent through the thalamus to the auditory cortex
  (temporal lobes)

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Theories of Hearing Place or Frequency?

• Hermann von Helmholtz (1863)
• Place theory
• Other researchers (Rutherford, 1886)
• Frequency theory
• Georg von Bekesy (1947)
• Traveling wave theory

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Auditory LocalizationWhere Did that Sound Come
From?

• Two cues critical
• Intensity (loudness)
• Timing of sounds arriving at each ear
• Head as shadow or partial sound barrier
• Timing differences as small as 1/100,000 of a
  second

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Figure 4.48 Cues in auditory localization
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The Chemical Senses Taste

• Taste (gustation)
• Physical stimulus soluble chemical substances
• Receptor cells found in taste buds
• Pathway taste buds - neural impulse - thalamus
  - cortex
• Four primary tastes sweet, sour, bitter, and
  salty
• Taste learned and social processes

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Figure 4.49 The tongue and taste
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The Chemical Senses Smell

• Smell (Olfaction)
• Physical stimuli substances carried in the air
• dissolved in fluid, the mucus in the nose
• Olfactory receptors olfactory cilia
• Pathway Olfactory cilia - neural impulse -
  olfactory nerve - olfactory bulb (brain)
• Does not go through thalamus

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Figure 4.51 The olfactory system
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Skin Senses Touch

• Physical stimuli mechanical, thermal, and
  chemical energy impinging on the skin.
• Pathway Sensory receptors - the spinal column
  - brainstem - cross to opposite side of brain
  - thalamus - somatosensory (parietal lobe)
• Temperature free nerve endings in the skin
• Pain receptors also free nerve endings
• Two pain pathways fast vs. slow

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Figure 4.53 Pathways for pain signals
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Other Senses Kinesthetic and Vestibular

• Kinesthesis - knowing the position of the various
  parts of the body
• Receptors in joints/muscles
• Vestibular - equilibrium/balance
• Semicircular canals