The Stroop Effect (1)

1
The Stroop Effect (1)
Red Blue Green Black Green Blue
2
The Stroop Effect (2)
Green Red Blue Black Blue Red
3
Definitions

• Sensation
• The process of stimulating receptors
• Perception
• Interpretation selection of sensory input

4
(No Transcript)
5
(No Transcript)
6
(No Transcript)
7
(No Transcript)
8
(No Transcript)
9
(No Transcript)
10
(No Transcript)
11
(No Transcript)
12
The Retina

• Made of about 107 million transducers

100 million rods 7 million cones
13
Rods

• Mostly in the periphery
• More light sensitive
• Detect light and dark
• Insensitive to red
• Take 20-30 minutes to fully adapt to darkness

14
Cones

• Mostly in the fovea
• Less light sensitive
• Detect colors
• Have best detail vision
• Adapt fully to darkness in 2-3 minutes

15
The Young-Helmholtz trichromatic theory
16
The Opponent Process Theory

• Cells are connected so as to place sensations of

• red in opposition to green
• blue in opposition to yellow
• black in opposition to white

17
Color Vision

• The trichromatic theory explains perception at
  the receptor level
• The opponent process theory explains it at higher
  brain levels

18
Seeing Afterimages
In the following slide, fix your eyes on the dot
in the center of the flag
19
(No Transcript)
20
(No Transcript)
21
Lateral Inhibition

• Cells in the retina are connected laterally by
  amacrine cells
• Works to enhance contrasts

22
Lateral Inhibition
See the glowing white spots where the black lines
cross?
23
Ear Structures
24
Ear Structures

• Pinna The external ear. Amplifies sound. Funnels
  energy to the middle ear.
• Typanic Membrane (eardrum) Moves in response to
  sound waves. Converts sound energy to mechanical
  energy .
• Ossicles The hammer (maleus), anvil (incus),
  stirrup (stapes). Transmit amplify motion of
  eardrum

25
Ear Structures

• Cochlea A fluid-filled chamber. Hair cells are
  attached to the basilar membrane . Converts
  mechanical energy to neural impulses.
• Bone Conduction Sound is also transmitted to the
  cochlea through contact with skull bones. This is
  why your voice sounds odd in recordings

26
Hearing

• Sound Attributes
• Pitch determined by frequency
• Loudness determined by amplitude
• Timbre Complexity of the sound (number of
  component waves involved in it)

27
Sound Waves
28
Hearing Loss
Hair cells, once lost, do not regenerate Even
some children's toys can cause permanent hearing
loss
29
Hearing Loss
Usually caused by continuous exposure to
excessive noise The louder the noise, the less
exposure needed
30
Chemical Senses

• Consist of smell taste
• Evoke memories, emotions
• Humans vary greatly in chemical sensitivity

31
Olfaction (Smell)

• Senses vaporized molecules
• Consists of 10 million rods embedded in the
  olfactory epithelium

32
Olfaction (Smell)

• Olfactory Bulbs Matchstick-sized Integrate
  signals from the olfactory rods, send them on to
  the brain
• Turbinate Bones Filter out dust and warm
  incoming air. Protect the olfactory epithelium.
• Olfactory Rods There are more than 100 different
  types. Each responds to different chemicals

33
Smell Sensitivity

• Sense of smell varies among animals
• Dogs have 200 million olfactory rods, spread out
  in a much bigger nose
• Humans differ greatly in ability to detect smells
• The most sensitive people are 20 times more
  sensitive than the least

34
Taste Buds

• The least numerous sensory receptors
• (humans have only about 10,000)

35
Taste

• Involves only 4 sensations Sweet, sour, salty,
  bitter
• Most of what we consider taste is actually smell
• Texture is very important in enjoyment of food
• People love fats for the smooth feeling they give
  food (most are tasteless)

36
Taste Changes

• There are no taste buds in the center of the
  tongue
• Taste buds constantly replaced (like olfactory
  rods)
• Taste sensitivity changes very little with age
• Enjoyment of food among the aged is reduced by
  loss of sense of smell

37
Somasthetic Senses

• Kinesthetic sense A moving sense
• Vestibular sense Being oriented
• Touch Feeling well
• Temperature

38
Skin Senses

• The largest sensory apparatus, involves heat,
  cold, pressure, pain
• Sensitivity varies throughout the body, reflected
  in the amount of brain devoted to each section of
  skin
• The hands face predominate

39
Pain

• Important for survival
• Motivates us to protect the body, tend injuries,
  rest, seek medical help.
• Gate Theory
• Suggests an area in the spinal cord where
  fast-conducting nerve fibers can block the
  messages of small, slow conducting fibers.
• Suggests humans can block pain even when severely
  injured
• Explains why the badly injured may not even
  notice an injury

40
Endorphins

• Slow firing of pain neurons
• Accupuncture placebos work through endorphin
  release
• "Runner's high" involves endorphin production
• Can be blocked by endorphin-blocking drugs

41
Body Senses

• Kinesthetic Sense
• Knowledge of the position and motion of body
  parts.
• Driven by receptors in muscles, joints, and
  ligaments
• Vestibular Sense
• Involves the semicircular canals the vestibular
  sacs
• Senses acceleration, not uniform motion
• Motion sickness arises when vision and the
  vestibular sense give rise to different messages

42
Subliminal Persuasion

• Influence by messages that are below your level
  of awareness
• Ex taped messages that are below auditory
  level
• Double-blind studies have found little support
  for the efficacy of subliminal persuasion tapes
  (See the following example.)

43
Subliminal Persuasion

• Example
• In one study, subjects were given audio tapes
  labeled for weight loss.
• Half were given actual weight loss tapes
• Half were given smoke-ending tapes
• Results

The tapes with subliminal anti-smoking messages
were just as effective as those with weight-loss
messages. The label mattered, not the messages.
44
Extra-Sensory Perception

• Telepathy Detecting others' thoughts
• Clairvoyance Knowing things that can't be sensed
• Precognition Predicting the future
• Psychology is concerned with evidence
• Evidence of psychic ability under controlled
  conditions is lacking

Consider this If you could read minds, couldn't
you find something more worthy (and profitable)
for your talent than to do cheap parlor tricks?
45
Definitions-Psychophysics

• Absolute Threshold
• The point where you can tell the stimulus is
  there vs. not there 50 of the time
• Difference Threshold
• The smallest change in the stimulus that is just
  detectable 50 of the time

46
Psychophysics A World of Experience

• Detecting signals
• Signal detection theory
• Sensitivity
• Bias

47
Intermediate Vision

• Perceptual organization
• Figure
• Ground

48
Figure-Ground

• We organize the world so some parts of a
  stimulus appear to stand out (figure) in front of
  other parts (ground)

49
Gestalt Principles

• The whole is greater than the sum of its parts.
• A group of sensory elements forms something new
  that is greater than itself

• Good Continuation
• Closure
• Simplicity

• Figure-Ground
• Similarity
• Proximity

50
Similarity

• We group things that are similar in color, shape,
  etc. into single units and see them as belonging
  together
• Note in the following example how similarity
  alters our perception of the stimulus as rows vs.
  columns of circles

51
Similarity
Repeat
52
Proximity

• We perceive as a unit things that are closer
  together relative to other things
• Note the tendency to see the next example as a
  set of columns first, then a set of rows, despite
  the fact the horizontal distance between circles
  doesn't change

53
Proximity
Repeat
54
Good Continuation

• We group things together if they appear to form a
  continuous pattern
• Example lines are continued through if they
  cross other lines
• In the next example, we see the stimulus as a
  wavy line crossing a straight line, although
  numerous other interpretations are possible.

55
Good Continuation
Repeat
56
Closure

• We tend to complete figures with gaps in them,
  by ignoring the gaps and mentally filling in what
  we believe should be there

57
Good Continuation
Repeat
58
Simplicity

• We tend to impose the simplest, best-fitting
  interpretation on any stimulus.
• In the following picture, we tend to see
  overlapping simple geometric figures rather than
  complex polygons.

59
Good Continuation
Repeat
60
(No Transcript)
61
(No Transcript)
62
Depth Perception

• Cues can be monocular or binocular
• Some appear to be innate, whereas others appear
  to be learned

63
Binocular Cues

• Convergence -- the lenses of your eyes move
  closer together when things are close, farther
  apart when things are farther away

64
Convergence
Repeat
65
Binocular Cues

• Binocular Disparity --
• Each eye gets a different picture of the world
• The greater the difference between the pictures,
  the closer the object

66
Monocular Cues

• Linear Perspective --
• parallel lines converge into the distance
• Relative Size --
• bigger things appear to be closer
• Texture Gradient --
• textures become finer as things become more
  distant.

67
Monocular Cues

• Shading --
• Shadowing distinguishes bulges from indentations
• Largely a learned cue
• Motion Parallax --
• Objects closer than our fixation point move
  opposite to our direction of motion.
• Objects farther away move in the same direction
  as us.

68
Monocular Cues

• Overlap or Interposition --
• Closer objects overlap objects that are farther
  away

69
Monocular Cues
Linear Perspective
Relative Size
Overlap
70
Visual Illusions

• Reveal information about the visual system
• Sometimes derive from perspective cues

71
(No Transcript)
72
(No Transcript)
73
The Bending Lines Illusion
Repeat
74
(No Transcript)
75
Illusions
Repeat
76
Depth Cues
77
Ambiguous Images

• Have 2 interpretations, can be switched at will
• Demonstrate the existence of top-down processing

78
The Schroeder Staircase
79
Impossible Images

• Changing perspective gradually in a large picture
  can create impossible figures (as in some Escher
  prints).
• If the figure is large enough, you cannot
  perceive it all at once, so the change in
  perspective is not readily apparent.
• Contrast the relative ambiguity of the large and
  small figures on the next slide.

80
2 Tongs/ 3 Tongs
81
Another Impossible Figure
82
(No Transcript)
83
Late Vision

• Knowing more than you can see
• Informed perception
• Perceptual expectancies

84
(No Transcript)
85
(No Transcript)