Sensation and Perception

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Sensation and Perception

• Chapter 3
• George S. Robinson, Jr., Ph.D.
• Department of Psychology
• North Carolina AT State University

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Sensation and Perception

• Sensation
• activation of receptors by stimuli
• Perception
• organizing and interpreting sensory information
• Transduction
• converting stimuli from the receptors to an
  electrochemical pattern
• Adaptation
• loss of sensitivity to a stimulus due to repeated
  stimulation of a receptor

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Sensation and Perception
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Psychophysics

• Psychophysics
• the relationship between stimuli and the
  participants experience
• Absolute threshold
• minimum amount of energy of a stimulus that can
  be detected 50 percent of the time
• Webers Law
• the size of a just noticeable difference is a
  constant proportion of the size of the initial
  stimulus
• Just Noticeable Difference (JND)
• smallest difference between two stimuli that can
  be detected 50 percent of the time

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Signal Detection Theory

• A threshold varies with the nature of the
  stimulus (signal) and background stimulation
  (noise)

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The Visual Stimulus

• Wavelength
• Amplitude
• saturation
• radiant light
• reflected light

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Visual System

• Accommodation
• conjunctive eye movements
• vergence eye movements
• retina
• rods
• cones
• fovea
• bipolar cells
• blind spot
• optic chiasm

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Visual System - cont.
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Theories of Color Vision

• Trichromatic theory (Young-Helmholtz)
• there are three types of color receptors

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Theories of Color Vision - cont

• The Opponent Process Theory
• red - green
• when red is active green is inhibited and vice
  versa
• bleu - yellow
• when blue is active yellow is inhibited and vice
  versa
• color after images
• perception of color that is not really present
  occurs after viewing the opposite or
  complimentary color

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Color Afterimage

• Focus on the dot in the center of the flag for 30
  seconds auto advance

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Color Deficiencies

• Monochromat
• person who sees only shades of gray very rare
• Dichromat
• person who has trouble seeing one of the primary
  colors (red, green or blue)
• Anomalous trichromat
• form of colorblindness in which one of the three
  primary colors (red, green or blue) is processed
  incorrectly

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Test of Color Deficiency
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The Auditory Stimulus

• Wavelength (frequency, Hertz)
• amplitude (intensity, Decibel)
• Purity (timbre)
• Hearing range 20 - 20,000 Hertz

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The Auditory System

• Pinna
• Auditory canal
• Eardrum
• Ossicles
• hammer (malleus), anvil (incus), stirrup (stapes)
• Oval window
• Basilar membrane
• Organ of Corti
• Tectorial membrane
• place theory
• frequency theory

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Hearing Disorders

• Conduction deafness
• deafness from transmitting sound through the
  outer and middle ear
• Sensorineural deafness
• deafness from damage to the inner ear, especially
  the hair cells
• central deafness
• deafness caused by disease and tumors in the
  auditory pathways or auditory cortex

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Sounds and Damage to the Auditory System
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Taste (Gustation)

• Taste buds
• structures that contain the taste receptors, each
  bud contains about 20 receptors
• Papillae
• bumps on the tongue and in the throat that are
  lined with taste buds
• Microvilli
• hairs that project from taste buds

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Taste - cont.
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Smell (Olfaction)

• Olfactory bulb
• Olfactory receptors
• cilia
• 100 different type of receptors
• lock-and-key
• pattern of receptors

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Other Sensory Systems

• Vestibular Sense
• allows us to make adjustments to bodily movements
  and posture
• semicircular canals
• fluid filled passages in the inner ear
• utricle
• fluid filled chamber in the inner ear that
  detects changes in gravity

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Other Sensory Systems - cont.

• Kinesthetic sense
• receptors located in the muscles and joints that
  provide information about the location of the
  extremities
• Somatosensory Processing
• mechanoreceptors - touch or pressure
• thermoreceptors - temperature receptors

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Other Sensory Systems - cont.

• Skin receptors
• Meissner corpuscles
• light touch
• Merkel Disks
• steady pressure
• Ruffini endings
• pressure of large objects, stretching of the skin
• Pacinian corpuscles
• very sensitive to touch
• Free nerve endings
• temperature and pain

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Sensitivity to Touch
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Other Sensory Systems - cont.

• Pain
• nocioreceptors
• receptors that respond to painful stimuli
• gate control theory
• endorphins
• substance P

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Perception

• Motivational influences
• Attention
• divided attention
• dichotic listening

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Perception - cont.

• Patterns and Constancies
• pattern perception
• feature detectors
• feature analysis theory
• we perceive basic elements of an object, and
  assemble them mentally to create a whole
• bottom-up approach (model)
• top-down approach (model)

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Pattern and Constancies - cont

• Perceptual constancies
• shape constancy
• size constancy
• Depth Perception
• binocular cues
• convergence (eye muscles)
• binocular (retinal) disparity
• Monocular cues
• superimposition, texture gradient, linear
  perspective, relative brightness

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Depth Perception - Visual Cliff
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Gestalt Principles of Perceptual Organization

• Figure-ground relationships

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Gestalt Principles of Grouping

• Proximity
• similarity
• continuation
• closure
• inclusiveness

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Perception of Movement

• Apparent Motion (autokinetic effect)
• illusion of movement in a stationary object
• television
• movies
• video games

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Perceptual Hypothesis and Illusions

• Perceptual hypothesis
• inferences about the nature of stimuli received
  from the environment
• Perceptual illusions
• misperceptions or interpretations of stimuli that
  do not correspond to the sensations received

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Perceptual Illusions
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Perceptual Illusions - cont.
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Extrasensory Perception (ESP)

• Clairvoyance
• to see hidden objects
• telepathy
• to perceive the thoughts or emotions of others
• Precognition
• knowledge of the future
• Psychokinesis (telekinesis)
• ability of the mind to influence matter

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• Zener cards
• Ganzfeld (total field)