Sensation

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Sensation PerceptionChapter 5
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Sensing Perceiving Information

• Sensation Receiving
• Perception Organizing Interpreting

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Vision The Eye

• Light enters eye through the cornea
• Passes through the pupil and lens
• Focused into an image on the retina
• Retina
• Light sensitive inner surface of the eye
• Contains Rods Cones
• Receptor cells convert light to neural impulses
  and send to brain
• Brain reassembles impulses into an image

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Vision The Eye
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Vision Retina Receptors

• Rods
• detect black, white, and gray
• necessary for peripheral and twilight vision
• Cones
• concentrated near the center of retina
• function in daylight or well-lit conditions
• detect fine detail
• color vision

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Vision--Receptors
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The Eye

• Optic Nerve nerve that carries neural impulses
  from the eye to the brain
• Blind Spot point at which the optic nerve leaves
  the eye
• No receptor cells
• creates a blind spot

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Vision Feature Detection

• Feature Detectors
• nerve cells that respond to specific features of
  a stimulus
• shape, angle, or movement
• fMRI can be used to determine what object a
  person is looking at

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Visual Information Processing

• Parallel Processing
• processing many parts of a problem all at once
• the brains natural mode of information
  processing for many functions (including vision)

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Visual Information Processing
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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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Color Vision

• Young-Helmholtz trichromatic (three-color) theory
• retina has 3 different color receptors (red,
  green, blue)
• different combinations allow for the perception
  of any color
• Opponent-process theory
• opposing processes of retina enable color vision
• e.g., some neurons are turned on by red and off
  by green

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Audition

• 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
• long sound waves low frequency low pitch
• short sound waves high frequency high pitch

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Audition--The Ear

• Sound waves
• auditory canal ?eardrum (vibrates with the waves)
  ?middle ear ?cochlea (in inner ear) ? triggers
  neural impulses (auditory nerve) ? thalamus ?
  auditory cortex (temporal lobe)
• Middle Ear
• chamber between the eardrum and cochlea
• contains 3 tiny bones (hammer, anvil, stirrup)
  that transmit vibrations to the cochlea

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Audition--The Ear

• Inner Ear
• innermost part of ear
• Contains the Cochlea
• a fluid-filled tube through which sound waves
  trigger nerve impulses

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Decibel Levels - Common Sounds
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Locating Sounds

• sound reaches one ear more intensely and more
  quickly
• auditory system is able to detect tiny
  differences
• hearing loss in one ear difficulty locating
  sounds

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Touch

• Skin Sensations
• pressure
• only skin sensation with identifiable receptors
• warmth
• cold
• pain
• Rubber hand illusion
• http//www.youtube.com/watch?vTCQbygjG0RU

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Pain

• No theory explains all available findings
• Gate-Control Theory (1960s)
• provides a useful model for understanding pain
• the spinal cord contains small fibers (conduct
  pain signals) and large fibers (conduct other
  sensory signals)
• 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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Pain Control

• Massaging area next to pain
• Distraction
• Diverting the brains attention may bring relief
• Pleasant imagery
• Count backward
• Virtual reality

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Taste

• Taste Sensations
• sweet
• sour
• salty
• bitter
• savory (umami)

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Taste

• Taste receptors
• reproduce themselves every 2 weeks
• taste sensitivity and of taste buds decrease as
  we age
• Sensory Interaction
• one sense may influence another sense
• the smell of food influences its taste
• smell texture flavor
• rubber hand illusion (vision touch interact)

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Smell

• humans can detect 10,000 odors
• olfactory receptor cells
• respond to aromas
• messages sent through receptor axons to the
  olfactory bulb in the brain
• messages then travel from olfactory bulb to
  temporal lobe limbic system
• odors can evoke memories

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Smell
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Body Position and Movement

• Sixth sense
• Kinesthesis
• the system for sensing the position and movement
  of individual body parts
• interacts with vision
• Vestibular sense
• monitors head and body position to maintain
  balance
• fluid in the inner ear moves when head moves
• messages are sent to the cerebellum

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Perceptual Organization- organizing
interpreting info from senses

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

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Perceptual Organization

• First Need to discriminate objects from
  backgrounds
• Figure and Ground perceiving an object (figure)
  as distinct from its surroundings (ground)
• In a busy restaurant
• voice you attend to figure
• all other voices ground

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Perceptual Organization- Gestalt

• Next step Need to organize the figure into a
  meaningful form
• Grouping
• the tendency to organize stimuli into meaningful
  groups
• grouping rules identified by Gestalt
  psychologists
• the whole that we perceive differs from the sum
  of its parts

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Perceptual Organization- Gestalt

• Grouping Rules
• proximity - we group nearby figures together
• similarity - we group similar figures together
• continuity we perceive continuous patterns
• closure we fill in gaps to create complete
  objects
• connectedness - spots, lines, and areas are seen
  as a unit when connected

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

• Depth Perception
• seeing objects in three dimensions
• allows us to estimate distance
• Visual Cliff
• laboratory technique used to test depth
  perception
• http//www.youtube.com/watch?veyxMq11xWzM

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Perceptual OrganizationDepth Perception

• Binocular cues
• depth cues
• depend on use of two eyes
• retinal disparity
• images from the two eyes differ
• brain compares the images to compute distance
• the larger the difference, the closer the object

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Perceptual OrganizationDepth Perception

• Monocular Cues
• depth cues needed for objects at further
  distances
• available to each eye separately
• relative height
• higher objects seen as more distant
• relative size
• smaller image is more distant

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Depth Perception

• Monocular Cues (continued)
• interposition
• if one object blocks our view of another, we
  perceive that object to be closer

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Depth Perception

• Monocular Cues (continued)
• relative clarity
• hazy object seen as more distant
• relative motion
• as we move, stable objects appear to also move
• fix gaze on object those beyond appear to move
  with you those in front appear to move backward
• relative brightness
• dimmer objects seem farther away

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Depth Perception

• Monocular Cues (continued)
• linear perspective
• parallel lines appear to converge with distance

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Perceptual Constancy

• perceiving objects as unchanging despite changes
  in illumination and retinal image
• able to recognize objects despite changes in
  color, shape, size

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Shape Constancy
Shape constancy as a door opens the shape
projected on retina looks more like a
trapezoidbut we still perceive it as
rectangular.
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Perceptual Constancy

• Color depends on context
• Color Constancy
• we perceive familiar objects as having consistent
  color
• even if illumination changes and alters the
  wavelengths reflected by the object

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Perceptual OrganizationSize-Distance Relationship
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Perceptual Organization- Size-Distance
Relationship
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Depth Perception
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Perceptual OrganizationMüller-Lyer Illusion
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Perceptual OrganizationBrightness Contrast
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Perceptual Interpretation

• Perceptual Adaptation
• (vision) ability to adjust to an artificially
  displaced visual field
• glasses that invert view of the world (looks
  upside down)
• humans can adapt relatively quickly and learn to
  coordinate movements accurately

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Perceptual Interpretation

• Perceptual Set
• a mental predisposition to perceive one thing and
  not another
• our experiences and expectations influence what
  we perceive

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Perceptual Set context effect
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Is There Extrasensory Perception?

• Parapsychology
• the study of paranormal phenomena
• Astrological predictions
• Psychic healing
• ESP
• Psychokinesis (mind over matter levitating)

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Is There ESP?

• Extrasensory Perception (ESP)
• controversial claim that perception can occur
  apart from sensory input
• types of ESP
• Telepathy (mind-to-mind communication)
• Clairvoyance (sensing remote events)
• Precognition (perceiving future events)