Sensation and Perception

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Sensation and Perception

• Modules 11 - 16

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Sensation

• Module 11

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Sensation

• The process by which our sensory systems (eyes,
  ears, and other sensory organs) and nervous
  system receive stimuli from the environment
• A persons awareness of the world

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Bottom-Up Processing

• Information processing that focuses on the raw
  material entering through the eyes, ears, and
  other organs of sensation

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Perception

• The process of organizing and interpreting
  sensory information

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Top-Down Processing

• Information processing that focuses on
  expectations and experiences in interpreting
  incoming sensory information

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Thresholds

• Module 11 Sensation

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Threshold

• Threshold
• An edge or a boundary

• Absolute Threshold
• The minimum difference that a person can detect
  between two stimuli 50 of the time
• Also called just noticeable difference

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JND

• Webers Law two stimuli must differ by a
  constant proportion for their difference to be
  noticed

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Thresholds Signal Detection Theory

• Module 11 Sensation

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Signal Detection Theory

• Set of formulas and principles that predict when
  we will detect the presence of a faint stimulus
  (signal) amid background stimulation (noise)
• Developed out of the Cold War

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Signal Detection Theory

• Three kinds of variables
• Stimulus variables
• Environmental variables
• Organismic variables

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Subliminal Stimulation

• Below threshold stimulation
• We can process information without being aware of
  it
• There is a subtle effect on thinking
• Subliminal advertising is not effective

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Sensory Adaptation

• Module 11 Sensation

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Sensory Adaptation

• Diminished sensitivity as a result of constant
  stimulation
• If a stimulus is constant and unchanging,
  eventually a person may fail to respond to it

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Selective Attention

• Module 11 Sensation

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Selective Attention

• Focusing conscious awareness on a particular
  stimulus to the exclusion of others
• The ability to focus on one stimulus at a time
• Allows a person to function in a world filled
  with many stimuli

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The Visual System The Nature of Light

• Module 12 Sensation

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Electromagnetic Energy

• An energy spectrum that includes X-rays, radar,
  and radio waves
• A small portion of the spectrum includes light
  visible to the human eye

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The Electromagnetic Spectrum
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Hue

• The color of light as determined by the
  wavelength of the light energy
• Includes red, orange, yellow, green, blue,
  indigo and violet (ROY G BIV)
• The eye can detect 7 million separate hues

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Wavelength
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Amplitude

• The brightness of light as determined by height
  of the wave
• The taller the wave, the brighter the color

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Amplitude
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The Visual System The Structure of the Visual
System

• Module 12 Sensation

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Cornea

• The clear bulge on the front of the eyeball
• Begins to focus the light by bending it toward a
  central focal point
• Protects the eye

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Parts of the Eye Cornea
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Iris

• A ring of muscle tissue that forms the colored
  portion of the eye creates a hole in the center
  of the iris (pupil)
• Regulates the size of the pupil by changing its
  size--allowing more or less light to enter the
  eye

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Parts of the Eye - Iris
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Pupil

• The adjustable opening in the center of the eye
  that controls the amount of light entering the
  eye (surrounded by the iris)
• In bright conditions the iris expands, making the
  pupil smaller.
• In dark conditions the iris contracts, making the
  pupil larger.

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Parts of the Eye - Pupil
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Lens

• A transparent structure behind the pupil focuses
  the image on the back of the eye (retina)
• Muscles that change the thickness of the lens
  change how the light is bent thereby focusing the
  image
• Glasses or contacts correct problems in the lens
  ability to focus.

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Parts of the Eye - Lens
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Retina

• Light-sensitive surface with cells that convert
  light energy to nerve impulses
• At the back of the eyeball
• Made up of three layers of cells
• Receptor cells
• Bipolar cells
• Ganglion cells

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Parts of the Eye - Retina
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Receptor Cells

• These cells are present in every sensory system
  to change (transduce) some other form of energy
  into neural impulses.
• In sight they change light into neural impulses
  the brain can understand.
• Visual system has two types of receptor cells
  rods and cones

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Rods

• Visual receptor cells located in the retina
• Can only detect black and white
• Respond to less light than do cones

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Cones

• Visual receptor cells located in the retina
• Can detect sharp images and color
• Need more light than the rods
• Many cones are clustered in the fovea.

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Fovea

• The central focal point of the retina
• The spot where vision is best (most detailed)

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Parts of the Eye - Fovea
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Bipolar Cells

• Gather information from the rods and cones and
  pass it on to the ganglion cells
• Cells that form the middle layer in the retina

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Ganglion Cells

• Pass the information from the bipolar cells
  through their axons
• Together these cells form the optic nerve.
• The top layer of the cells in the retina

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Visual Processing in the Retina
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Visual Processing in the Retina
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Visual Processing in the Retina
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Visual Processing in the Retina
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Optic Nerve

• The nerve that carries visual information from
  the eye to the occipital lobes of the brain

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Parts of the Eye Optic Nerve
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Blind Spot

• The point at which the optic nerve travels
  through the retina to exit the eye
• There are no rods and cones at this point, so
  there is a small blind spot in vision.

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Parts of the Eye Blind Spot
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The Visual System Color Vision

• Module 12 Sensation

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Trichromatic (three-color) Theory

• Theory of color vision that says cones are
  tuned to be sensitive to red, green and blue
  light
• All the colors we see are a combination of these
  three colors.
• Based on work of Helmholtz and Young
• Similar to the design of a color TV

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Subtractive Color Mixing

• When mixing colored paints, each new color
  SUBTRACTS (soaks up) another wavelength.
• Red, blue, and yellow combine to make black paint.

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Additive Color Mixing

• When mixing colored lights, each new color ADDS
  another wavelength.
• Red, green, and blue combine to make white light.

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Color Deficient Vision

• People who lack one of the three types of cones
• Usually the red or green receptors are missing
• Usually referred to as color blindness
• In inherited and found more in males

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Opponent-Process Theory of Color

• Theory that says color is processed in opponent
  pairs of color
• Red-green, yellow-blue, black-white
• Light that stimulated one half of the pair
  inhibits the other half
• Ewald Hering
• Explains the afterimage effect

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Afterimage Effect
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Hearing The Nature of Sound

• Module 13 Sensation

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Sound

• Sound, like light, comes in waves
• Sound is vibration
• Features of sound include
• Pitch
• Hertz
• decibels

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Pitch

• A sounds highness or lowness
• Dependent on the frequency of the sound wave
• Is measured as hertz (Hz)

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Hertz (Hz)

• A measure of the number of sound wave peaks per
  second measures frequency
• Determines the pitch of the sound
• Human hearing goes from 20 Hz to 20,000 Hz

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Decibel (dB)

• A measure of the height of the sound wave
• Determines the loudness of the sound
• Sometimes called amplitude

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Hearing The Structure of the Auditory System

• Module 13 Sensation

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Parts of the Ear Sound Waves
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Auditory Canal

• The opening through which sound waves travel as
  they move into the ear for processing
• Ends at the tympanic membrane (eardrum)

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Parts of the Ear Auditory Canal
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Tympanic Membrane (eardrum)

• The tissue barrier that transfers sound vibration
  from the air to the tine bones of the middle ear
• Can be damaged by objects in the ear or
  exceptionally loud noises

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Parts of the Ear Tympanic Membrane
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Ossicles

• Three tiny bones that transfer sound waves from
  the eardrum to the cochlea
• Hammer, anvil and stirrup

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Parts of the Ear - Occicles
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Cochlea

• A hearing organ where sound waves are changed
  into neural impulses
• The major organ of hearing
• Filled with fluid a snail shaped body tube

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Parts of the Ear - Cochlea
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Oval Window

• The point on the surface of the cochlea which
  receives the sound vibration from the ossicles
• As the oval window vibrates, the fluid in the
  cochlea vibrates.

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Parts of the Ear Oval Window
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Hair Cells

• The receptor cells for hearing in the cochlea
  that change sound vibrations into neural impulses
• Similar to the rods and cones within the eye

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Parts of the Ear - Hair Cells
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Auditory Nerve

• The nerve that carries sound information from the
  ears to the temporal lobes of the brain

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Parts of the Ear Auditory Nerve
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Semicircular Canals

• Organs in the inner ear used in sensing body
  orientation and balance (vestibular sense)
• Relies on fluid in the canals
• Spinning in circles disrupts the fluid.

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Parts of the Ear Semicircular Canals
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Divisions of the Ear

• Ears structure can be divided into
• The outer ear
• The middle ear
• The inner ear

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Divisions of the Ear
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Divisions of the Ear
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Divisions of the Ear
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Hearing Sound Localization

• Module 13 Sensation

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Localization of Sound

• Locating where sound is originating from
• Done through two cues
• Which ear hears the sound first?
• Which ear hears the louder sound?

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Localization of Sound
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Other Senses Touch

• Module 14 Sensation

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Touch

• Touch receptors are on the skin
• Four basic skin senses are
• Pain, warmth, cold, and pressure
• All skin sensations are a combination of these
  four basic senses

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Gate-control Theory of Pain

• Pain messages travel on one set of nerve fibers
  containing pain gates.
• The gates are open when pain is felt.
• Other sensory messages go through another set of
  fibers.
• The nonpain fibers can close the pain gates to
  stop the sense of pain.

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Other Senses Taste

• Module 14 Sensation

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Taste

• Taste is a chemical sense.
• Receptor cells are located primarily on the
  tongue and in the mouth.
• Four different tastes
• Salty, sweet, sour and bitter
• Damaged taste receptor cells are replaced within
  a few days.

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Supertasters

• People with an abundance of taste receptors
• Approximately 25 of the population

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Nontasters

• People with a minimum of taste receptors
• Taste with less intensity than the rest of the
  population
• Approximately 25 of the population

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Other Senses Smell

• Module 14 Sensation

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Smell

• Smell is a chemical sense.
• Olfactory cells in the upper nasal passages
  detect molecules in the air.
• Taste and smell interact to produce flavor.

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Olfactory Cells

• The chemical receptor cells for smell
• Located in the nasal passages

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Smell
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Smell
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Smell
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Other Senses Body Senses

• Module 14 Sensation

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Kinesthetic Sense

• The system for sensing the position and movement
  of individual body parts
• Relies on receptor cells from the muscles and
  joints
• Ones leg falling asleep is a disruption of the
  kinesthetic sense

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Vestibular Sense

• The system for sensing body orientation and
  balance
• Relies on fluid in the semicircular canals of the
  inner ear
• Spinning in circles disrupts the fluid.

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Parts of the Ear Semicircular Canals