1. As the intensity of the brightness of a light is increased, the sizes of the action potentials of the neurons involved:a. increaseb. decreasec. stay the samed. first increase, then decrease

3. A blind experimental design should be sufficient to eliminate:a. placebo effectsb. experimenter effectsc. self-selectiond. 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 cortexb. medullac. cerebellumd. 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 bottleneckc. 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 lobeb. primary motor cortexc. thalamusd. 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

INCREASES TARGET BEHAVIOR

DECREASES TARGET BEHAVIOR

Positive Reinforcement(Lever Press Food pellet)

+ Add something good

Positive Punishment(Lever Press Shock)

+ Add something bad

Negative Reinforcement(Lever Press Shock off)

- Take away something bad

Negative Punishment(Lever Press removes food)

- Take away something good

Goal

Manip

ula

tion

Neg

ati

ve

(Rem

ovin

g s

om

eth

ing

)

Posit

ive

(In

trod

ucin

g s

om

eth

ing

)

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.).

ITIT + IB

IB

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

Stimulus Neural Response Sensation

Behavior Yes, No

Noise(Apparatus)

Noise(Spontaneous firing rates.

Genetic variation)

Noise(Criterion.

Response bias.)

Psychophysics: Psychophysical “Laws”

“Typical” Weber experiment:IB IB+IT ΔI ΔI/I k

10 11 1 1/10 = 0.120 22 2 2/20 = 0.150 55 5 5/50 = 0.1

Ernst Weber1795-1878

Weber Constants:

Brightness ~ 1/80 = 1.25%Loudness ~ 1/80 = 1.25%Saltiness ~ 1/5 = 20%

Weber’s Lawjnd = kI

Psychophysics: Fechner’s “Law” (logarithmic law of sensory magnitude)

Gustav Fechner1801-1887

Psychophysics: Stevens’ “Law” (power law of sensory magnitude)

•Stevens’ Power Law

S = c M 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

Forced-choice Preferential Looking

Habituation/Dishabituation

Forced-choice Preferential Looking

50

60

70

80

90

100

0 5 10 15

Intensity Increment from Surround

Tes

ter'

s P

erce

nt C

orr

ect

Data

Psychometric function

Threshold

Functional Organization of the Eye

Transduction Occurs in the Retina

Sensory Receptors

CONES: permit sharply focused color vision Fovea ~6 million

RODS: permit vision in dim light Everywhere else ~120 million

Transduction

RHODOPSIN: the photochemical in rods that undergo structural changes in response to light Rod opsin and retinal

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 Sensitivity (or ability to see

in dim light)

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

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 cellEncodes 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 Feature-Integration 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

PROXIMITY•Stimulus elements that are close to each other are perceived as belonging to the same object

SIMILARITY•We tend to see stimulus elements that physically resemble each other as parts of the same object

CLOSURE•We tend to see forms as completely enclosed by a border and to ignore gaps in the border

Gestalt Principles of Perceptual Grouping

GOOD CONTINUATION•When lines intersect, we tend to group the line segments in such a way as to form continuous lines with minimal change in direction

COMMON MOVEMENT•When stimulus elements move in the same direction and speed, we tend to see them as part of the same object

GOOD FORM•The perceptual system strives to produce percepts that are elegant—simple, uncluttered, regular and predictable

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-by-Components Theory

Our visual system organizes the stimulus information into a set of basic, three-dimensional 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 Perspective4. Texture Gradient

5. Position Relative to the Horizon6. 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