1. As the intensity of the brightness of a light is increased, the sizes of the
action potentials of the neurons involved:
a. increase
b. decrease
c. stay the same
d. first increase, then decrease
3. A blind experimental design should be sufficient to eliminate:
a. placebo effects
b. experimenter effects
c. self-selection
d. non-random selection
13. Which area of the brain acts as a relay station, directing most
incoming sensory information to a proper region of the cerebral cortex?
a. sensory cortex
b. medulla
c. cerebellum
d. thalamus
14. Which of the following is NOT an example of genetic drift:
a. A species of bird must change its location once a new predator arrives. The
climate of the new location is warmer than the previous, and in several generations,
the species sheds its formerly thick layer of feathers.
b. Evolutionary bottleneck
c. The group of individuals that colonized an area near the Arctic circle just happened
to have higher rates of schizophrenia. Therefore, the current population has a higher
rate of schizophrenia.
d. All of these are examples of genetic drift.
21. A study in a scientific journal has revealed that there is a significant
difference between the IQs of males and females. Which of the following
statements about the p-value must be true?
a. The p-value should be very high in order to obtain significance.
b. The p-value should be very low in order to obtain significance.
c. The p-value must be exactly 5% in order to obtain significance.
d. The p-value can be anything; it doesn’t have anything to do with significance.
28. Which of the following brain areas, when damaged, would most likely lead
to the cessation of breathing?
a. parietal lobe
b. primary motor cortex
c. thalamus
d. brainstem
7. Sheldon uses positive reinforcement to make Penny behave in a favorable
way. He gives her a piece of chocolate following a desired behavior. If,
instead, he chose to use negative reinforcement, which of the following
actions would he take?
a. Relieve her of her daily chores when she behaves well.
b. Spray her with a bottle of water every time she misbehaves.
c. Take away her Wi-Fi privileges every time she misbehaves.
d. Buy her a gift card to her favorite store when she behaves well.
Reinforcement and Punishment
Positive
(Introducing
something)
Negative
(Removing
something)
Manipulation
Goal
INCREASES TARGET
BEHAVIOR
DECREASES TARGET
BEHAVIOR
Positive Reinforcement
(Lever Press  Food
pellet)
Positive Punishment
(Lever Press  Shock)
+ Add something good
+ Add something bad
Negative Reinforcement
(Lever Press  Shock off)
Negative Punishment
(Lever Press  removes
food)
- Take away something bad
- Take away something good
7. Sheldon uses positive reinforcement to make Penny behave in a favorable
way. He gives her a piece of chocolate following a desired behavior. If,
instead, he chose to use negative reinforcement, which of the following
actions would he take?
a. Relieve her of her daily chores when she behaves well.
b. Spray her with a bottle of water every time she misbehaves.
c. Take away her Wi-Fi privileges every time she misbehaves.
d. Buy her a gift card to her favorite store when she behaves well.
19. Which of the following is NOT true about the theory of evolution?
a. Humans and monkeys share common ancestry.
b. Evolution describes the origin and development of life.
c. Natural selection ensures that one living species is never more evolved than
another.
d. Evolution is not a moral force.
Psychophysics & The
Psychology of Vision
Chapter 8
Psychophysical Thresholds
Absolute Threshold

PSYCHOPHYSICS: Relationship
between physical
characteristics of stimuli and
the sensory experience that
the stimuli produce

ABSOLUTE THRESHOLD: the
faintest stimulus of a given
sensation that an individual
can detect
Difference Threshold
 DIFFERENCE THRESHOLD: the
minimal difference that must
exist between two otherwise
similar stimuli for an individual to
detect them as different (jnd)
Psychophysics
Psychophysical function – measuring sensation.
Ratio scale: Absolute Threshold (A.L.) represents
sensory zero. Difference Threshold (ΔI) represents
sensory step (just-noticeable-difference – j.n.d.).
IB
IT
IT + I B
Psychophysics: Classical Methods
Adjustment. Limits (ascending; descending). Constant Stimuli.
Constant Stimuli:
Fixed set of stimuli (6 –
10), above & below
expected threshold;
presented in random
order. Set repeated
several times to obtain
“% Yes” for each
stimulus. Threshold
derived by interpolation.
Psychophysics: Variability
Noise
Noise
Noise
(Apparatus)
(Spontaneous firing rates.
Genetic variation)
(Criterion.
Response bias.)
Stimulus
Neural
Response
Sensation
Behavior
Yes, No
Psychophysics: Psychophysical “Laws”
Weber’s Law
jnd = kI
“Typical” Weber experiment:
IB IB+IT ΔI ΔI/I
k
10
20
50
11
22
55
1 1/10 = 0.1
2 2/20 = 0.1
5 5/50 = 0.1
Weber Constants:
Brightness ~ 1/80 = 1.25%
Loudness ~ 1/80 = 1.25%
Saltiness ~ 1/5 = 20%
Ernst Weber
1795-1878
Psychophysics: Fechner’s “Law”
(logarithmic law of sensory magnitude)
Gustav Fechner
1801-1887
Psychophysics: Stevens’ “Law”
(power law of sensory magnitude)
• Stevens’ Power Law
S=cM
p
 S is the magnitude of the
sensory experience, c is
a proportionality
constant, M is the
magnitude of the
physical stimulus and p is
the constant power
Psychophysics: Infants
Habituation/Dishabituation
Forced-choice Preferential Looking
Forced-choice Preferential Looking
100
Tester's Percent Correct
Data
Psychometric function
90
80
70
60
Threshold
50
0
5
10
Intensity Increment from Surround
15
Functional Organization of the
Eye
Transduction Occurs in the Retina
Sensory Receptors
Transduction
 CONES: permit sharply
focused color vision
 RHODOPSIN: the
photochemical in rods that
undergo structural changes
in response to light
 Rod opsin and retinal
 Fovea
 ~6 million
 RODS: permit vision in dim
light
 Everywhere else
 ~120 million
 The breakdown of rhodopsin
creates an electrical charge
that initiates an action
potential on the neurons of
the OPTIC NERVE
Differences Between Cone and
Rod Vision
 Cone vision = PHOTOPIC vision
 Color perception and high
acuity
 Rod vision = SCOTOPIC vision
 DARK ADAPTATION: the
increased visual sensitivity that
occurs when the eyes are
exposed for a period of time to
dimmer light than was present
before the adaptation period
 Sensitivity (or ability to see in
dim light)
 LIGHT ADAPTATION: the
decreased visual sensitivity that
occurs when the eyes are
exposed for a period of time to
brighter light than was present
before the adaptation period
The Electromagnetic Spectrum
Types of Color Mixing
 SUBTRACTIVE-COLOR MIXING:
the mixing of pigments
whereby each pigment
absorbs a different set of
wavelengths of light that
would otherwise be reflected
to the eye
 ADDITIVE-COLOR MIXING: the
mixing of colored lights by
superimposing them to reflect
off the same surface
 Three-primaries law
Two Classic Theories of Color Vision
The Trichromatic
Theory
•
Theory proposed by Young
and Helmholtz to explain the
three-primaries law of color
vision; it holds that the human
ability to perceive color is
mediated by three different
types of receptors, each of
which is most sensitive to a
different range of
wavelengths
•
3 cone types: red, green and
blue
Differences in Cone
Wavelengths
Two Classic Theories of Color
Vision
The Opponent-Process Theory
• Theory proposed by Hering to explain the law of
complementarity; it holds that units (neurons) that
mediate the perception of color are excited by
one range of wavelengths and inhibited by
another (complementary) range of wavelengths
540nm
640nm
+G – R cell
Encodes the
presence of green
(the absence of red).
Color Blindness
Protanopia
Deuteranopia
Tritanopia
Enhancement
of Contours
 CONTOURS: sudden
changes in brightness or
color that separate objects
from their background
Treisman’s Two-Stage FeatureIntegration Theory of Perception
1. Detection of Features
•
PARALLEL PROCESSING: the
early steps in the analysis of
sensory information that act
simultaneously on all of the
stimulus elements that are
available at any given
moment
✖
2. Integration of Features
•
SERIAL PROCESSING: steps in
the process of sensory
information that operate
sequentially on the
available sensory
information
∨
Support for Treisman’s Theory
O
Gestalt Principles of Perceptual
Grouping
Gestalt Principles of Perceptual
Grouping
Figure and Ground
 FIGURE: that which calls
your attention
 GROUND: the background
 REVERSIBLE FIGURE: a visual
stimulus in which any given
part is seen sometimes as
the figure and other times
as the ground
The Whole Can Affect the Perception
of the Parts
Illusory Contours
Illusory Lightness
Differences
Biederman’s Recognition-byComponents Theory
 Our visual system organizes
the stimulus information
into a set of basic, threedimensional components
(GEONS), and then uses
the arrangement of those
components to recognize
the object
The Man Who Mistook His Wife For
A Hat
• VISUAL AGNOSIA: condition caused by
damage to specific portions of the
occipital and temporal lobes of the
cortex, in which people cannot make
sense of what they see
• VISUAL FORM AGNOSIA: a type of
agnosia in which people can identify
some elements of what they see but
cannot perceive an object’s shape
• VISUAL OBJECT AGNOSIA: a type of
agnosia in which people can identify
and draw the shapes of objects but
cannot identify the objects
Two Pathways of Visual
Processing in the Brain
 The “what” pathway
 Occipital lobe  temporal
lobe
 Disrupts recognition of
object
 Can manipulate the object
 The “where and how” pathway
 Occipital lobe  parietal
lobe
 Can recognize the object
but interaction with the
object is disrupted
Cues for
Depth
Perception
 BINOCULAR DISPARITY: cue
for depth perception that
stems from the separate
views the eyes have of any
given object or visual scene
 The farther away the
object is, the more similar
are the two views of it
 The degree of disparity
between the two eyes’
views can serve as a cue to
judge an object’s distance
from the eyes
Monocular Cues for Depth
• MOTION PARALLAX: cue
for depth perception that
stems from the changed
view one has of a scene or
object when one’s head
moves sideways to the
scene or object
1.
Occlusion
2.
Relative image size for
familiar objects
Monocular Cues for Depth
3. Linear Perspective
4. Texture Gradient
5. Position Relative to the Horizon
6. Differential Lighting of Surfaces
The Role of Depth Cues in Size
Perception
Size Constancy
The Ames Room
Unconscious Depth Processing as
a Basis for Size Illusions
The Ponzo Illusion
The Müller-Lyer Illusion