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Sensation and Perception. Chapter 4. The Basics. Sensation – Involves the stimulation of sensory receptors and the transmission of sensory information to the central nervous system i.e. spinal cord and brain Things that tip off sensory receptors: Light, sound, smells, etc. The Basics.

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Presentation Transcript
the basics
The Basics
  • Sensation – Involves the stimulation of sensory receptors and the transmission of sensory information to the central nervous system
          • i.e. spinal cord and brain
  • Things that tip off sensory receptors:
      • Light, sound, smells, etc.
the basics1
The Basics
  • Perception – How we interpret sensory stimulation
      • Football field example
    • Perception reflects learning, expectations and attitudes
absolute threshold
Absolute Threshold
  • The weakest amount of a stimulus that can be tested
      • Dogs v. Humans
    • Thresholds are different amongst people
        • More sensitive than others
slide5

Some established absolute thresholds are:

vision: a candle flame 30 miles away on a clear night.

hearing: a watch ticking 20 feet away

taste: 1 teaspoon of sugar dissoved in 2 gallons of water

smell: a single drop of perfume in a three-room house

touch: a bee\'s wing falling a distance of 1 centimeter onto the cheek.

difference threshold
Difference Threshold
  • The minimum amount of difference detected between two stimuli
      • Tone
      • Hue
      • Piles of sand
signal detection theory
Signal-Detection Theory
  • Distinguishing sensory stimuli that takes into account all factors of self and environment
  • We focus on what we consider important
sensory adaptation
Sensory Adaptation
  • Process by which we become more sensitive to weak stimuli and less sensitive to unchanging stimuli
    • Eyes adapting to darkness
    • Waves on a beach
    • Traffic
section 2 vision
Section 2 - Vision
  • Color spectrum – Roy G. Biv
the eye
The Eye
  • Similar to a camera
  • Light enters the eyes, and then is projected onto a surface
    • The amount of light that enters is determined by the opening in the colored part of the eye
          • The pupil
the eye1
The Eye
  • Once light enters, it meets the lens
    • The lens adjusts to distances of objects by changing its thickness
          • Finger test – near / far
the eye2
The Eye
  • The changes in thickness and light project a clear image onto the retina
    • The retina acts like the film of a camera
    • Neurons in your retina that are sensitive to light are called photoreceptors
    • Once the photoreceptors are activated a nerve carries the information to the brain – occipital lobe
the blind spot
The Blind Spot
  • We need the blind spot to see
  • A point left empty of photoreceptors – room for information to travel
        • Circle test
rods and cones
Rods and Cones
  • 2 kinds of photoreceptors
    • Rods – sensitive only to the brightness of light
    • Cones – provide color
dark and light adaptation
Dark and Light Adaptation
  • Your ability to see in low light improves for 45 minutes
      • Sundown
  • Adaptation to light happens much more quickly
visual acuity
Visual Acuity
  • Vision tests for sharpness
    • 20/20
  • As you age your lenses become brittle, and you may become farsighted
      • Holding reading material further away
color vision
Color Vision
  • Human beings can see up to 1 million different hues
      • Animals are more sensitive to certain colors
  • The color circle
  • Afterimages
  • Color blind – distinguishing colors from each other
      • Total color blindness is extremely rare
section 3
Section 3
  • Hearing – a series of vibrations in the form of sound waves in its own unique pitch or loudness
    • Hearing experiment
pitch
Pitch
  • The more cycles (sound waves) per second, the higher the pitch (high or low)
    • Women’s voices are at a higher pitch than men’s because their vocal cords tend to be shorter
    • Humans – 20 to 20,000 per second
    • Dogs / Dolphins / other animals in excess of 20,000
loudness
Loudness
  • Measured in dB (decibels)
    • Loudness is determined by the height / amplitude of sound waves
          • 0 decibels is the threshold (a watch heard ticking at 20 feet away)
locating sound
Locating Sound
  • Perception of sound
      • Infinite possibilities
    • How your body / senses react to sound
deafness
Deafness
  • Inherited / Disease / Injury / Old Age
  • Conductive Deafness –
    • Damage to middle ear, sound is not amplified
      • Helped with hearing aides
  • Sensorineural Deafness
    • Damage or elimination of neurons, damage to auditory nerve
      • Cannot be helped if nerve itself is damaged
      • Cochlear implants can help neuron loss
section 4
Section 4
  • Other Senses –
    • Smell – incredibly important, apples and onions would be relatively the same otherwise
    • Taste – Spheres of the tongue
      • Smell and taste work together when eating
skin senses
Skin Senses
  • Touch
  • Infants grow quickly and stay healthier if touched
    • Older people do better if they have pets (cats / dogs)
  • Body is covered in hairs, many too small to see
    • Sensory receptors lie at the base of the hair
  • Do we actually “touch”?
temperature
Temperature
  • Differences are all relative
    • Fevers
    • Outside heat (Summer)
    • Swimming pools
    • A/C
slide26
Pain
  • The more pain receptors are located in a certain body, they more we will feel
  • Point of contact > Spine > Thalamus > Brain (processing)
    • Prostaglandins help transmit messages
          • Ibuprofen and aspirin help slow prostaglandins
slide27
Pain
  • Why does rubbing or scratching painful areas help?
      • Mixed signals
  • Phantom limb pain
body senses
Body Senses
  • Vestibular Sense
    • Sensory organs in your ears monitor your motion and relation to gravity
        • Balance, standing, changing speeds, etc.
  • Kinesthesis
    • Position and motion of your body
    • Copying body motions
section 5
Section 5
  • Perception – the way our body makes sense of our sensory impressions
  • Gestalt psychology – “The whole is more than the sum of its parts”
rules of perceptual organization
Rules of Perceptual Organization
  • Closure – filling in the gaps to get a complete picture
    • Fig 4.11 (p. 93)
          • Filling in the blanks because dogs are familiar to you
rules of perceptual organization1
Rules of Perceptual Organization
  • Figure-Ground Perception
    • What do we perceive as the figure and what do we perceive as the background
          • Fig 4.12 (Vases or Faces)
rules of perceptual organization2
Rules of Perceptual Organization
  • Other Rules -
    • Laws of:
      • Proximity
      • Similarity
      • Continuity
      • Common Fate
rules of perceptual organization3
Rules of Perceptual Organization
  • Perception of Movement
    • To sense movement we need a change of position
    • Your senses need clues to tell you that you are moving
        • Trees, road bumps, etc.
rules of perceptual organization4
Rules of Perceptual Organization
  • Stroboscopic Motion
    • The illusion of movement
      • Flipbooks
      • Movies on reels
        • Subliminal messages
    • Perception smoothes out the gaps
    • Humans prefer smooth images
rules of perceptual organization5
Rules of Perceptual Organization
  • Depth Perception
    • The “distance away”
    • Monocular clues – the appearance of 3-D on 2-D surfaces
        • i.e. paintings
          • Clearness, shadow, texture, overlapping, perspective
    • This is done through stimulation of retina
monocular cues
Monocular Cues
  • Clearness – faraway objects seem less detailed
  • Perspective – parallel lines coming together or moving apart
  • Overlapping – placing of one object in front of another
  • Shadows and highlights – give a 3-D feel
  • Texture Gradient – closer objects have more texture (gradient – progressive change)
  • Motion parallax – the tendency of objects to seemingly move forward or backward depending on distance away
      • Moon, stars v. trees and rocks while driving
binocular cues
Binocular Cues
  • Need both eyes v. one eye for monocular
    • 2 cues in binocular:
      • Retinal Disparity
      • Convergence
binocular cues1
Binocular Cues
  • Retinal Disparity – only works on objects that are very close
    • Difference of angles of an object as seen by both retinas
  • Convergence – associated with a tightness of the eye muscles on things up close
    • Magic Eye puzzles
perceptual constancies
Perceptual Constancies
  • Size Constancy – Comes through experience
    • Perceiving an object as one size no matter the distance
    • Pygmy example p. 98
perceptual constancies1
Perceptual Constancies
  • Color Constancy
    • The tendency for objects to maintain color no matter the light quality
  • Brightness Constancy
    • Tendency to find an object equally bright even when its surroundings change
perceptual constancies2
Perceptual Constancies
  • Shape Constancy
    • The knowledge an item has one shape
          • i.e. top of a glass from different angles
visual illusions
Visual Illusions
  • When the rules of constancies are violated
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