Sensation and Perception

1
Sensation and Perception

• Senses Touch, Auditory (hearing), Taste, Optic
  (vision), Vestibular (balance), Olfactory
  (smell), Kinesthetic (motion) and -----ESP?
• Perceptions Images, Psychological, and
  Physiological

2
Sensation and Perception

• Sensation detect physical energy from the
  environment and encode it as neural signals
• Perception selection, organization, and
  interpretation of our senses

3
Thresholds

• Psychophysics study of the relationship between
  the physical energy and our psychological
  experience. (What stimuli can we detect? - At
  what levels of intensity? - How sensitive are
  we to changing stimulation?)
• Absolute Thresholdsminimum stimulation necessary
  to detect a particular stimulus
  (light-sound-pressure-taste-odor)
• Signal Detection Detecting a weak stimulus, or
  signal, depends not only on the signals
  strength, but also on our psychological state
  (experience, expectations, motivations, and
  fatigue)

4
(No Transcript)
5
(No Transcript)
6
(No Transcript)
7
(No Transcript)
8
(No Transcript)
9
Thresholds cont

• Difference Thresholds (just noticeable
  difference) the minimum difference a person can
  detect between any two stimuli 50 of the time
• Webers Law two stimuli must differ by a
  constant proportion for their difference to be
  perceptible our threshold for detecting
  differences are roughly constant proportion of
  the size of the original stimulus
• Sensory Adaptation our diminishing sensitivity
  to an unchanging stimulus (ex. move watch up
  wrist an inch)

10
Taste

• 4 qualities of taste (sweet, sour, bitter, salty)
• Taste Pore, Taste Cell and Taste Neuron
• Humans vary in amount of taste buds hence their
  sensitivity to taste
• 25 have less than 1000 (nontasters) 25 have
  10,000 (supertasters) 50 in the middle

11
(No Transcript)
12
Smell (olfaction)

• 6-10 mill olfactory receptors located in 1sq inch
  of olfactory epithelium at the top of each
  nostril
• Axons of olfactory receptors pass directly thru
  skull to brain olfactory bulb
• Females tend to have a better odor sense than
  males.
• Olfactory input is then sent to parts of the
  brain that deal with emotion and memory(certain
  smell triggers emotion and memory)

13
(No Transcript)
14
(No Transcript)
15
Audition (Hearing)

• 15,000 auditory receptors called hair cells
  inside the cochlea
• Different pitches maximally stimulate different
  places along the basilar membrane
• Waves vary in length, and therefore in Frequency
• Frequency determines pitch (longer the wave,
  lower the frequency lower the pitch) (shorter
  the wave, higher the frequency higher the
  pitch)
• Placement of ears allows Stereophonic hearing
  (three-dimensional)

16
(No Transcript)
17
(No Transcript)
18
(No Transcript)
19
Vision

• Sense Sight, Receptors Rods (light) Cones
  (color) both in Retina
• Rods - 120 mill/eye very sensitive respond in
  dim light (night vision)
• Cones - 6 mill/eye need bright light detail
  vision 3 different types provide color vision
• Fovea retinas area of central focus (only
  cones, no rods)

20
Blind Spot

• Blind Spot point where the optic nerve leaves
  the eye is the blind spot
• When light hits the brain registers nothing
  because the area lacks photoreceptorsneurons
  that are sensitive to light

21
Try this

• Make a dot with your pencil/pen on your paper.
  Then, about 3 inches to the right of that dot,
  draw a small car. (see below).
• Then, close your left eye, look at the dot, and
  move your page to a distance at which the car
  disappears. Theres your blind spot!

22
Vision

• Farsighted Nearsighted Normal
  Vision Vision Vision

23
Nearsightedness/Farsightedness

• Shape of eyeballsperfect shape, perfect vision
• Eyeball too longNearsightedness you can see
  objects that are near, but not distant
• Eyeball too short/squattyFarsightedness you
  can see objects that are distant, but not near

24
(No Transcript)
25
(No Transcript)
26
Depth Perception

• Retinal disparity differences between the images
  on the two retinas (is essential to your sense of
  depth perception)
• Brain interprets a large retinal disparity
  between the Rt/Lf eyes as an object that is
  nearby
• Brain interprets a small retinal disparity Rt/Lf
  eyes as an object that is distant.
• Stereopsis both eyes working together to give us
  depth perception

27
(No Transcript)
28
Color Deficiencies

• Cones do not function properly he/she is color
  deficient
• Red/Green color blindness (some folks)
• Yellow/Blue color blindness (fewer folks)
• Achomatopsia total colorblindness (rare)
• 8 of men and 1 of women color deficiencies

29
If you see the 74 no color blindness If you see
only 21 some color blindness If you see nothing
total color blindness
30
Red Green color blindness
31
Binocular Fusion

• Eyes located about 2.5 apart
• Visual system receives two images, instead of
  seeing double, we see a single, fused image.

32
After-Image Opponent - Process

• Opponent Process information is analyzed in
  terms of the opponent colors red and green, blue
  and yellow, and black and white.
• After tiring your neural response to black, green
  and yellow you should see their opponent colors

33
(No Transcript)
34
(No Transcript)
35
(No Transcript)
36
(No Transcript)
37
(No Transcript)
38
(No Transcript)
39
(No Transcript)
40
(No Transcript)
41
(No Transcript)
42
Touch

• Neural impulses from different parts of the skin
  surface take different amounts of time to reach
  the brain
• Four senses pressure, warmth, cold, and pain
  that combine to produce other sensations (such as
  hot)
• Sensitivity to pressure varies from place to
  place depending on how populated that area is
  with receptors (fingertips)

43
Sensation- Thresholds

• Webers Law- to perceive a difference between
  two stimuli, they must differ by a constant
  proportion
• Ex Hersheys Bar price increase from 50 cents to
  55 cents more noticeable than 40,000.00 car
  price increase to 40,000.05still increased same
  amount, but the percentage of change is what
  raises eyebrows.
• Sensory adaptation- diminished sensitivity with
  constant stimulation
• Ex. Vanilla Smell
• Ex. Locker room
• What about Vision?

44
(No Transcript)
45
Pain Gated Sense

• Message sent to the CNS using transmitter called
  Substance P
• Built-in Gate determines whether the pain
  message gets to brain full force or whether the
  gate will close and dampen the pain messages
• Both Psychological(motivation, laughter) and
  Physiological (other sensory stimulation,
  endorphins, narcotic pain relievers) can help
  close the gate

46
Body Position and Movement

• Kinesthesis sense of our body parts position
  and movement
• Equilibrium monitors the position and movement
  of the whole body (inner ear)
• i.e. Twirling around and come to a abrupt halt,
  the fluid in your semicircular canals and your
  kinesthetic receptors does not immediately return
  to its neutral state (aftereffect fools your
  brain that your still spinning dizzy)

47
(No Transcript)