Sensation and Perception

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Chapter 3
Sensation and Perception
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Overview

• Sensations include- smells, sights, sounds,
  tastes, balance, touch, and pain
  
• Perception- the mental process of sorting,
  identifying, and arranging information into
  meaningful patterns
  
• Both are the foundation of consciousness

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The Nature of Sensation

• The Basic Process
• Producing a sensation
• - stimulation of receptor cell
• - receptor sends a signal along the
  
  
• sensory nerves
• - different channels of brain for
• different sensory messages

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cont. The Nature of Sensation

• Doctrine of Specific Nerve Energies
• - one to one relationship between
• stimulation of specific nerve and
  type
  
• of sensory experience
• Decoding the senses
• - different stimuli affect which
• neuron, how many neurons, and
  rate
  
• of fire

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Sensory Threshold

• absolute threshold- least amount of energy that
  can be detected as a stimulation 50 percent of
  the time
  
• adaptation adjustment of the senses to the level
  of stimulation they are receiving
  
• difference threshold
• Webers Law

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Subliminal Perception

• People can be influenced by information of which
  they are not consciously aware
  
• In a controlled laboratory setting people can
  process and respond to information of which they
  are not consciously aware
  
• Advertisers put hidden messages and images in
  their advertisements?
  

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Extrasensory Perception

• ESP- a response to an unknown event not presented
  to any known sense
  
• clairvoyance awareness of an unknown
• object or event
• Telepathy knowledge of someone elses
• thoughts or feelings
• Precognition foreknowledge of future
• events

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Vision

• most important sense
• Visual System
• - light enters the eye through the
  cornea
  
• - it then passes through the pupil
• - inside pupil light moves through
  the
  
• lens
• - lens changes shape to focus on
  objects
  
• either close or far

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Cross section of human eye
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Cont. Vision

• Blind spot place on the retina where the axons
  of all the ganglion cells leave the eye and where
  there are no receptors
  
• fovea- area of the retina that is the center of
  the visual field

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The Receptor Cells

• retina of each eye contains the receptor cells
  responsible for vision
  
• contains 2 kinds of receptor cells
• - rods
• -cones
• visual acuity the ability to visually
  distinguish fine details

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Adaptation

• dark adaptation process by which rods and cones
  become more sensitive to light
  
• light adaptation rods and cones become less
  sensitive to light
  
• afterimage sense experience that occurs after a
  visual stimulus has been removed
  

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From Eyes to Brain

• Messages from the eye must make their way to the
  brain for sight to occur
  
• Optic nerve carries message from each eye to the
  brain
  
• 1 million ganglion cells for every 125 million
  rods and cones
  
• Optic chiasm point near the base of the brain
  where some fibers in the optic nerve from each
  eye cross to the other side of the brain

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Right and Left Visual Field
Rods Cones
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Cont. From Eyes to Brain

• main destination for signals from the retina is
  the cerebral cortex
  
• feature detectors highly specialized to respond
  to particular elements in the visual field
  
• cortical blindness- caused by severe damage to
  the visual cortex

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Color Vision Properties of Color

• hue aspect of color that corresponds to names
• saturation vividness or richness of a hue
• brightness nearness of a color to white as
  opposed to black
  
• most people can identify about 150 distinct hues

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Theories of Color Vision

• pigments of color absorb light
• Trichromatic theory all color perception derives
  from three different color receptors in the
  retina
  
• Trichromats
• Dichromats
• Monochromats
• Opponent-process theory three sets of color
  receptors respond to determine the color you
  experience

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Subtractive Color Mixing
Additive Color Mixing
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Color Vision in Other Species

• Color is in the eye of the beholder
• Many animals have color vision
• Some animals can see colors that we cant

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Hearing

• for some animals, hearing is their most acute
  sense
  
• no species use sound to create music as
  extensively as humans do

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Sound

• a psychological experience created by the brain
  in response to changes in air pressure that are
  received by the auditory system
  
• frequency number of cycles per second in a wave
  
  
• amplitude is the magnitude of the wave
• hearing undergoes adaptation so that it can
  function optimally under a wide variety of
  conditions

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The Ear

• Hearing begins when sound waves strike the
  eardrum and cause it to vibrate
  
• prompts 3 tiny bones in the middle ear
• vibrations of the oval window are transmitted to
  the fluid inside the cochlea
  
• organ of corti lies on top of the basilar
  membrane and moves in sync with it
  

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How We Hear
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Neural Connections

• each ear sends messages to both cerebral
  hemispheres
  
• medulla is the switching station
• primary destinations are the auditory areas in
  the temporal lobes

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Theories of Hearing

• Place Theory pitch is determined by the location
  of greatest vibration on the basilar membrane
  
• Frequency Theory pitch is determined by the
  frequency with which hair cells in the cochlea
  fire
  
• Volley Principle auditory neurons can fire in
  sequence

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Hearing Disorders

• 28 million Americans suffer from partial or total
  deafness
  
• Common causes injury, infections, cigarette
  smoking, explosions, and long term exposure to
  loud noise
  
• treatments inlucde hearing aids, surgery,
  implants, and some day soon neurgenesis

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Deaf Culture

• children born with hearing disorders are
  suggested not to seek restoring their hearing
  
• high-pitched hum that persists even in the
  quietest room
  
• -sound that seems to come from in your
• head is called tinnitus

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The Other Senses Smell

• Detecting Common Odors
• Olfactory epithelium nasal membranes containing
  receptor cells sensitive to odors
  
• Olfactory bulb the smell center in the brain
• Communicating with Pheromones
• Pheromones chemical molecules that communicate
  information other members of a species, and
  influence their behavior
  
• Vomeronasal organ (VNO) location of receptors
  for pheromones in the roof of the nasal cavity
  

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Taste

• Flavor of food arises from a complex combination
  of taste and smell
  
• Taste buds structures on the tongue that
  contain the receptor cells for taste
  
• Each taste bud contains a cluster of taste cells
  that are replaced about every seven days
  

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Taste

• Some tastes we recognize are bitterness,
  saltiness, sourness, and sweetness.
  
• The tip of the tongue is most receptive to
  sweetness and saltiness, the back to bitterness,
  and the sides to sourness
  
• Papillae small bumps on the tongue that
  contain taste buds
  

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Taste

• Different parts of the tongue are more sensitive
  to different tastes
  
• Taste displays adaptation when you eat salted
  peanuts the saltiness is strong at first but
  gradually becomes less noticeable
  

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Kinesthetic and Vestibular Senses

• Kinesthetic senses senses of muscle movement,
  posture, and strain on muscles and joints
  
• Stretch receptors receptors that sense muscle
  stretch and contraction
  
• Golgi tendon organs receptors that sense
  movement of the tendons, which connect muscle to
  bone
  
• Vestibular senses the senses of equilibrium and
  body position in space
  
• Vestibular sacs sacs in the inner ear that
  sense gravitation and forward, backward, and
  vertical movement
  

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Sensations of Motion

• Certain kinds of motion trigger strong reactions
  in some people
  
• According to one theory, motion sickness stems
  from discrepancies between visual information and
  vestibular sensations, in other words, our eyes
  and our body sense are sending our eyes
  contradictory information

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The Skin Senses

• Our skin is our largest sense organ
• Various skin receptors gives rise to sensations
  of pressure, temperature, and pain
  
• Skin displacement of as little as .00004 inch can
  result in a sensation of pressure
  
• Our faces and hands our most sensitive to touch

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Pain

• Pain serves as a warning signal for our body
• Phantom limb phenomenon when people undergo
  amputation of an arm of leg, they often continue
  to feel that the limb is still there
  
• New research suggests that injuries stimulate the
  release of chemicals that convert free nerve
  endings from touch and pressure sensors into pain
  sensors

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Pain

• Individual Differences
• Gate control theory the theory that a
  neurological gate in the spinal cord controls
  the transmission of pain messages to the brain
  
• Biopsychological theory the theory that the
  interaction of biological, psychological, and
  cultural factors influence the intensity and
  duration of pain
• Alternative Approaches
• Placebo effect pain relief that occurs when a
  person believes a pill or procedure will reduce
  pain. The actual cause of the relief seems to
  come from endorphins

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Perception

• Perceptual Organization
• Figure entity perceived to stand apart from the
  background
  
• Ground background against which a figure
  appears
  
• Perceptual Constancies
• Perceptual constancy a tendency to perceive
  objects as stable and unchanging despite changes
  in sensory stimulation
  
• Size constancy the perception of an object as
  the same size regardless of the difference from
  which it is viewed
  
• Shape constancy a tendency to see an object as
  the same shape no matter what angle it is viewed
  from
  
• Color constancy an inclination to perceive
  familiar objects as retaining their color despite
  changes in sensory information
  

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Perceiving Distance and Depth

• The image of the world on the retina is
  essentially two-dimensional, yet we perceive the
  world as three dimensional thanks to our ability
  to perceive distance and depth
• Monocular cues visual cues requiring the use of
  one eye
  
• Binocular cues visual cues requiring the use of
  both eyes
  

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Perceiving Distance and Depth

• Monocular Cues
• Aerial perspective monocular cue to distance
  and depth based on the fact that more distant
  objects are likely to appear hazy and blurred
  
• Texture gradient monocular cue to distance and
  depth based on the fact that objects seen at
  greater distances appear to be smoother and less
  textured
• Linear perspective monocular cue to distance
  and depth based on the fact that two parallel
  lines seem to come together at the horizon
  
• Motion parallax monocular distance cue in which
  objects closer than the point of visual focus
  seem to move in the direction opposite to the
  viewers moving head, and objects beyond the
  focus point appear to move in the same direction
  as the viewers head

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Perceiving Distance and Depth

• Binocular Cues
• Stereoscopic vision combination of two retinal
  images to give a three-dimensional perceptual
  experience
  
• Retinal disparity binocular distance cue based
  on the distance between the images cast on the
  two retinas when both eyes are focused on the
  same object
• Convergence a visual depth cue that comes from
  muscle controlling eye movement as the eyes turn
  inward to view a nearby stimulus
  

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Perceiving Distance and Depth

• Locating Sounds
• Monaural cue cue to sound location that
  requires just one ear
  
• Binaural cue cue to sound location that
  involves both ears working together
  

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Perceiving Movement

• Autokinetic illusion the perception that a
  stationary object actually is moving
  
• Stroboscopic motion apparent movement that
  results from flashing a series of still pictures
  in rapid succession, as in a moving picture
  
• Phi phenomenon apparent movement caused by
  flashing lights in sequence, as on theater
  marquees
  

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Visual Illusions

• Perceptual illusion illusion due to misleading
  cues in stimuli that give rise to inaccurate or
  impossible perceptions
  

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Individual Differences and Culture

• Perception is a combination of information from
  our senses, past experiences, and the wiring of
  our brains
  

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Enduring IssuesDiversity Universality

• Our perception of our environment is influenced
  by our motivation, values, expectations,
  cognitive style, experience and culture, and our
  personality.

PARIS IN THE THE SPRING