Sensation and Perception

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• Chapter 5
• Sensation and Perception

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Sensation

• Sensation
• a process by which our sensory receptors and
  nervous system receive and represent stimulus
  energy
• Perception
• a process of organizing and interpreting sensory
  information, enabling us to recognize meaningful
  objects and events

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Sensation

• Our sensory and perceptual processes work
  together to help us sort out complex processes

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Sensation

• Bottom-Up Processing
• analysis that begins with the sense receptors and
  works up to the brains integration of sensory
  information
• Top-Down Processing
• information processing guided by higher-level
  mental processes
• as when we construct perceptions drawing on our
  experience and expectations

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Sensation

• Top-Down Processing

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Sensation

• Top-Down Processing

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Sensation

• Top-Down Processing

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Sensation

• Top-Down Processing

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Sensation

• Top-Down Processing

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Sensation

• Top-Down Processing

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Sensation - Basic Principles

• Psychophysics
• study of the relationship between physical
  characteristics of stimuli and our psychological
  experience of them
• Light- brightness
• Sound- volume
• Pressure- weight
• Taste- sweetness

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Sensation - Basic Principles

• Psychophysics
• Spatial Frequency-

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Sensation - Thresholds

• Absolute Threshold
• minimum stimulation needed to detect a particular
  stimulus 50 of the time
• Difference Threshold
• minimum difference between two stimuli required
  for detection 50 of the time
• just noticeable difference (JND)

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Sensation - Thresholds

• Subliminal
• When stimuli are below ones absolute threshold
  for conscious awareness

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Sensation - Thresholds

• Webers Law- to perceive as different, two
  stimuli must differ by a constant minimum
  percentage
• light intensity- 8
• weight- 2
• tone frequency- 0.3
• Sensory adaptation- diminished sensitivity as a
  consequence of constant stimulation

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Vision - Stabilized Images on the Retina
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Vision

• Wavelength
• the distance from the peak of one wave to the
  peak of the next
• Hue
• dimension of color determined by
• wavelength of light
• Intensity
• amount of energy in a wave determined by
• amplitude
• brightness
• loudness

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The spectrum of electromagnetic energy
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Vision - Physical Properties of Waves
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Vision
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Vision

• Accommodation- the process by which the eyes
  lens changes shape to help focus near or far
  objects on the retina
• Retina- the light-sensitive inner surface of the
  eye, containing receptor rods and cones plus
  layers of neurons that begin the processing of
  visual information

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Retinas Reaction to Light - Receptors

• Rods
• peripheral retina
• detect black, white and gray
• twilight or low light
• Cones
• near center of retina
• fine detail and color vision
• daylight or well-lit conditions

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Retinas Reaction to Light

• Optic nerve
• carries neural impulses from the eye to the brain
• Blind Spot
• point at which the optic nerve leaves the eye,
  creating a blind spot because there are no
  receptor cells located there

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Retinas Reaction to Light
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Vision - Receptors
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Pathways from the Eyes to the Visual Cortex
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Visual Information Processing

• Feature Detectors
• nerve cells in the brain that respond to
  specific features
• shape
• angle
• movement

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Visual Information Processing

• Parallel Processing
• simultaneous processing of several aspects of a
  problem simultaneously

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Visual Information Processing
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Visual Information Processing

• Trichromatic (three color) Theory
• Young and Helmholtz
• three different retinal color receptors
• red
• green
• blue

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Color-Deficient Vision

• People who suffer red-green blindness have
  trouble perceiving the number within the design

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Visual Information Processing

• Opponent-Process Theory - opposing retinal
  processes enable color vision
• ON OFF
• red green
• green red
• blue yellow
• yellow blue
• black white
• white black

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Opponent Process - Afterimage Effect
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Visual Information Processing

• Color Constancy
• Perceiving familiar objects as having consistent
  color, even if changing illumination alters the
  wavelengths reflected by the object

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Audition

• Visual Capture
• tendency for vision to dominate the other senses
• Audition
• the sense of hearing
• Frequency
• the number of complete wavelengths that pass a
  point in a given time
• Pitch
• a tones highness or lowness
• depends on frequency

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The Intensity of Some Common Sounds
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Audition - The Ear
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Audition - The Ear

• Middle Ear
• chamber between eardrum and cochlea containing
  three tiny bones (hammer, anvil, stirrup) that
  concentrate the vibrations of the eardrum on the
  cochleas oval window
• Inner Ear
• innermost part of the ear, containing the
  cochlea, semicircular canals, and vestibular sacs
• Cochlea
• coiled, bony, fluid-filled tube in the inner ear
  through which

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How We Locate Sounds
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Pain

• Gate-Control Theory
• theory that the spinal cord contains a
  neurological gate that blocks pain signals or
  allows them to pass on to the brain
• gate opened by the activity of pain signals
  traveling up small nerve fibers
• gate closed by activity in larger fibers or by
  information coming from the brain

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Taste

• Taste Sensations
• sweet
• sour
• salty
• bitter
• Sensory Interaction
• the principle that one sense may influence
  another
• as when the smell of food influences its taste

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Smell
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Body Position and Movement

• Kinesthesis
• the system for sensing the position and movement
  of individual body parts
• Vestibular Sense
• the sense of body movement and position
• including the sense of balance

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Perceptual Organization

• Gestalt
• organized whole
• tendency to
• integrate pieces of information into
• meaningful wholes

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Perceptual Organization

• Figure and Ground--organization of the visual
  field into objects (figures) that stand out from
  their surroundings (ground)

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Perceptual Organization- Gestalt

• Grouping
• the perceptual tendency to organize stimuli into
  coherent groups
• Grouping Principles
• proximity--group nearby figures together
• similarity--group figures that are similar
• continuity--perceive continuous patterns
• closure--fill in gaps
• connectedness--spots, lines, and areas are seen
  as unit when connected

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Perceptual Organization- Grouping Principles
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Perceptual Organization- Closure

• Gestalt grouping principles are at work here.

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Perceptual Organization- Grouping Principles

• Gestalt grouping principles are at work here.

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Perceptual Organization- Depth Perception
Visual Cliff
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Perceptual Organization- Depth Perception

• Depth Perception
• ability to see objects in three dimensions
• allows us to judge distance
• Binocular cues
• retinal disparity
• images from the two eyes differ
• closer the object, the larger the disparity
• convergence
• neuromuscular cue
• two eyes move inward for near objects

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Perceptual Organization- Depth Perception

• Monocular Cues
• relative size
• smaller image is more distant
• interposition
• closer object blocks distant object
• relative clarity
• hazy object seen as more distant
• texture coarse --gt close fine --gt distant

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Perceptual Organization- Depth Perception

• Monocular Cues (cont.)
• relative height
• higher objects seen as more distant
• relative motion
• closer objects seem to move faster
• linear perspective
• parallel lines converge with distance
• relative brightness
• closer objects appear brighter

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Perceptual Organization- Depth Perception
Relative Size
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Perceptual Organization- Depth Perception
Interposition
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Perceptual Organization- Depth Perception
Relative Height
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Perceptual Organization- Depth Perception
Light and Shadow
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Perceptual Organization- Depth Perception
Perspective Techniques
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Perceptual Constancy

• Perceptual Constancy
• perceiving objects as unchanging even as
  illumination and retinal image change
• color
• shape
• size

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Perceptual Organization
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Perceptual Illusions
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Perceptual Illusions
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Perceptual Organization- Size-Distance
Relationship
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Perceptual Organization-Brightness Contrast
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Perceptual Organization- Grouping Principles

• Impossible doghouse

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Perceptual Interpretation

• Perceptual Adaptation
• (vision) ability to adjust to an artificially
  displaced visual field
• prism glasses
• Perceptual Set
• a mental predisposition to perceive one thing and
  not another

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Perceptual Set- Schemas

• A little demonstration
• Will half the class close their eyes?

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Perceptual Set- Schemas

• What kinds of horn are used in jazz?

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Perceptual Set- Schemas

• What kinds of horn are used in jazz?

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Perceptual Set- Schemas

• A little demonstration, part B
• Will the other half of the class close their
  eyes?

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Perceptual Set- Schemas

• Can you name a famous movie actress from Black
  and White movies?

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Perceptual Set- Schemas

• Can you name a famous movie actress from Black
  and White movies?

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Perceptual Set- Schemas

• A little demonstration, part C
• As soon as you recognize something raise your
  hand.

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Perceptual Set- Schemas

• What do you see?

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Perceptual Set- Schemas

• What do you see?

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Perceptual Set- Schemas

• What you see in the center is influenced
  by perceptual set

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Perceptual Set- Schemas

• What you see in the center is influenced
  by perceptual set

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Perceptual Set- Schemas
Flying Saucers or Clouds?
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Extrasensory Perception

• Extrasensory Perception
• controversial claim that perception can occur
  apart from sensory input
• telepathy
• clairvoyance
• precognition
• Parapsychology
• the study of paranormal phenomena
• ESP
• psychokinesis