psyc 100 ch. 4 textbook notes

7/30/2019 PSYC 100 Ch. 4 Textbook Notes

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CHAPTER 4: SENSATION AND PERCEPTION- gravity provides cues for peoples judgment concerning the spatial orientation of their bodies

Figure: Ian Howard

- pioneer in sensation/perception research (binocular vision and human spatial orientation)

- used room that tilts sideways and plane that travels in a parabolic manner to experience normal,hypergravity and microgravity environment

- human relies on visual, gravity and body direction

>astronaut is dependent on visual cues

Sensation: Stimulation of the sense organs

Perception: selection, organization and interpretation of sensory inputs (into something meaningful)

A) Psychopyhsics: Basic Concepts and Issues

- study of physical stimulation and how it is translated into psychological experience

- Figure: Gustav Fechner

Thresholds: Looking for Limits

- the dividing point between the energy levels that have do and do not have a detectable ofeffect

- Absolute threshold: Minimum amount of stimulation that an organism can detect

> just noticeable from nothing

> also defined as: stimulus intensity detected 50% of the time

*Under ideal condition, human abilities to detect weak stimuli were greater than previously thought

Weighing the Differences: The Just Noticeable Difference (JND)

- JND: smallest difference in the amount of stimulation that a specific sense can detect (cousin of

absolute threshold)

Figure: Ernst Weber- the size of JND is a constant proportion of the size of the initial stimulus

> constant proportion: Weber fraction (differs for each sensory input)

> e.g: for lifting weight; 1/30.For 300grams object, should be able to detect the different with 310g

>> as stimuli increases in magnitude, JND becomes larger

Psychophysical Scaling

Unit of measurement: JND

- Fechners Law: the magnitude of a sensory experience is proportional to the number of JNDs that the

stimulus causing the experience is above the absolute threshold

- constant increments in stimulus intensity produce smaller and smaller increases in the perceived

magnitude of sensation

Signal-Detection Theory (this theory is describing chaos)

- detection of stimuli involves decision processes as well as sensory processes which are both

influenced by a variety of factors besides stimulus intensity

> your performance depends on the level of noise (the noiser it is, the harder it gets)

Significance: this theory replaces Fechners sharp threshold with the concept ofdetectability


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- measured in terms ofprobability and depends on decision-making processes as well as sensory

processes

Perception without Awareness

- introduces the Subliminal Perception: registration of sensory inputs without conscious awareness

> limen is another word for threshold. Subliminal means below threshold

- area of research: unconscious semantic priming, subliminal affective conditioning, subliminal mere

exposure effects, subliminal visual priming, subliminal psychodynamic activation ignore the obvious and focus on changes

B) Our Sense of Sight: The Visual System

B)i) The Stimulus: Light

- Light: electromagnetic radiation that travels as a wave

- Light varies in: amplitude (height) and wavelength (distance between peaks)

- Amplitude: affects perception of brightness

- Wavelength: Affects perception of colour

> Lights that humans see are mixture of several wavelengths

- Vision is a filter that enables human to sense but a small fraction of the world

The Eye: A Living Optical Instrument

- Purpose of eyes: channel information (light) to the retina and house the neural tissues

Flow of movement:

1) Light enters through cornea (transparent window); upside-down image is formed

2) Lens: transparent eye structure that focuses light on retina

> made of soft tissues that facilitates a process called accommodation

- close object: lens become rounder

- distant object: lens flatten

- farsightedness: can only see far object, close object becomes blurry

> image falls behind retina

- nearsightedness: can only see near object, distant object becomes blurry

- eyeball is too short

- iris: colored ring that surrounds the iris

- pupil: the opening at the centre of the eye, helps regulate amount of light that enter the eyes

> pupil constricts: less light enter, image becomes sharper


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> pupil dilates: more light enter, images become blurry

- saccades: constant eye movement that scans the environment and making brief fixation at various part

if stimuli

> even small reduction in this movement, our vision degrades

> people can track YOU by knowing your saccades

B)ii) The Retina: The Brains Envoy in the Eye

- neural tissue lining the inside back surface of the eye; absorbs light, processes images, sends visual

information to the brain

Visual Receptors: Rods and Cones

- Retina contains two types of receptors: Rods (elongate) and cones (stubbier)

- Rods: big in number, night vision and peripheral vision

> more sensitive to dim light

> density is greatest outside fovea and decreases towards its periphery

- Cones: small in number, daylight vision and color vision

> do not respond well to dim light

> provide better visual acuity: sharpness and precise detail

> concentrated in the centre of retina and decreases towards the periphery

- fovea contains only cone and visual acuity is the greatest here

> to focus, image is adjusted to the fovea

Dark and Light Adaptation

Dark Adaptation: eyes become accustomed to the light in low illumination

> require less light to see

> cones adapt more rapidly than rods

Light Adaptation: eyes become more accustomed to light in high illumination

*Both of these result from chemical change in rods and cones

*cones adapt more rapidly than rods (probably because it is smaller in number)

Information Processing in the Retina

- axons which depart from the eye through optic disk, carry visual information that is encoded into

neural impulses to the brain

- complex information processing goes on in the retina

- receptive field of a visual cell: the retinal area when stimulated affects the firing of that cell

> light in centre of its receptive field: increases the rate of firing of a visual cell

> light outside the centre of receptive filed: decreases the rate of firing of a visual cell

Effect:

- when receptive fields are stimulated, retinal cells send signal towards the brain and laterally

- Lateral Antagonism (Lateral inhibitory): neural activity in a cell opposes activity in surrounding cells

> allows retina to compare the light falling in the specific area against general lighting


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> significance: visual system can compute the relative amount of light at a point instead of reacting to

absolute levels of light

B)iii) Vision and the Brain

- visual input is meaningless until it is processed in the brain

http://www.youtube.com/watch?v=AoUgq8yy0Mo

Visual Pathways to the Brain

- optic chiasm: point where optic nerve from inside half of each eye cross over and then project to the

opposite half of the brain

Rationality: ensure that both hemispheres receive signals

The Flow:

1) Axons from the left halfof each retina carry signals to the left side of the brain and axons from the

right halfof each retina carry signals to the right side of the brain

2) After reaching optic chiasm, optic fiber nerves diverge along the pathways which projects to the

thalamus

> synaption occurs in the lateral geniculate nucleus (LGN); also visual signals are processed here andthen distributed to the occipital lobe

3) second visual pathway leaves optic chiasm proceeds to superior colliculus (an area in the midbrain)

before travelling through the thalamus and proceeds to the occipital lobe

> this 2nd pathway is the coordination of visual input with other sensory input

MAIN VISUAL PATHWAYS:

- magnocellular: processes information regarding brightness

- parvocellular: processes perception of color

-involved in parallel processing (simultaneous extracting different kinds of information from the same

input)

Information Processing in the Visual Cortex

Figures: David Hubel and Torsten Wiesel

- experiment to see what shape turns us on

- Result: primary visual cortex dont respond to dots but more sensitive to lines, edges, more complex

stimuli

Hubel:

- born in Windsor, Ontario

- went to McGill Uni

- interested in nervous system; influence by Wilder Penfield

- discovery: simple cell respond to line with correct width, oriented at the correct angle, located in the

correct position in its receptive field while complex cell respond to any position in their receptive

fields

- Conclusion: feature detectors; neuron that respond selectively to specific features of more complex

stimuli

- After visual input is processed in the primary visual cortex:

1) routed to other cortical areas for additional processing
http://www.youtube.com/watch?v=AoUgq8yy0Mohttp://www.youtube.com/watch?v=AoUgq8yy0Mohttp://www.youtube.com/watch?v=AoUgq8yy0Mo


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2) the signals travel 2 streams: ventral stream (identify the object details) and dorsal stream (process

the location of that object- motion and depth)

3) As signal move farther along the visual processing system, neurons become more specialized and

fussy with what turns them on and stimuli that activate them become more complex

Research Question: Why does the cortex have face detectors?

- Probably: adaptive significance over the course of evolution

- natural selection may have wired some brains of species to quickly respond to face

Identify: face perception exists since from infancy

- Visual agnosia: inability to identify object

- Visual prosopagnosis: inability to recognize familiar faces (but can recognize voice better)

- neurons in the ventral stream pathway that are involved in recognizing faces can learn from experience

Multiple Methods in Vision Research (McCollough Effect)

- after-image phenomenon that differs from other color after-image effects because it is contingent on

both colour and pattern/form

Figure: Peter Dodwell use patient that suffers from visual agnosia

Find out more: Mc Collough Effect

B)iv) Viewing the World in Color

The Stimulus for Color

- perceived color is a function of the dominant wavelength

- longest wavelength: red, shortest: violet

*color is a psycho interpretation and NOT a physical property of light

- wavelength: closely related to hue, amplitude to brightness and purity to saturation

Two kinds of color mixture:

- Subtracting: removing some wavelengths of the light leaving less light than original (object darker)

- Additive: imposing some wavelength of the light adding more light to the original

*pigment absorbs most wavelength

Trichromatic Theory of Color Vision

Figure: 1st

- Thomas Young, 2nd

Herman von Helmholtz (modified) in 1852

- Theory states that: human eyes have 3 receptors with differing sensitivities to different light

wavelengths (red, green and blue)

> based on this model: people can perceive all colours of rainbow because the eyes does its owncolor

mixing

- Color-blindedness: defect in the ability to distinguish color

> most people are dichromats: able to deal with 2 color channels

Opponent Process Theory of Colour Vision

- Complementary: pairs of colors that produce grey tone when mixed together

> after staring at a strong colour and then stare at white background, youll see an afterimage

> afterimage: a visual image that persists after a stimulus is removed


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> color of afterimage complements the color originally stared

Research Question: If colors are reduced to 3 channels, why are four color names required to describe

the full range of possible colors?

Figure: Ewald Hering (Opponent Process Theorist)

- states that : color perception depends on receptors that make antagonistic responses to three pairs of

colors.

- red vs green, yellow vs blue, black vs white

- also explain some aspects ofcolor-blindedness

- grapheme-color synethesia: individuals perceive digit or letter but somehow associate it with colors

- e.g: when you see number 7, you think of blue (unintentionally)

Reconciling Theories of Color Vision

- it takes both theories (trichromatic theory color of vision and opponent process theory color of

vision) to explain color vision

Figure: George Wald- demonstrates that eyes have 3 types of cones with each being sensitive to different type of band of

wavelengths

- 3 colors are predicted by trichromatic theory (red, green, blue)

Research discovery: Cells in the retina, the LGN and visual cortex respond in the opposite ways to red

vs green, blue vs yellow

Effects of Color on Behavior

Figure: Andrew Elliot

- colors can have automatic unconscious effects on behavior (improve or impair)

- hypothesis: exposure to the red color has a negative impact on performance

B)v) Perceiving Forms, Patterns and Objects

- reversible figure: drawings that are compatible with two interpretations that can shift back and forth

> same visual input can result in radically different perceptions

> peoples experience of the world is subjective

- perceptual set: a readiness to accept stimulus in a particular way (perception is readily built)

- form perception: depends on what people focus on

- inattentional blindness: failure to see fully visible objects or events in a visual display

> when asked to focus on something, the tendency to overlook details is high

- inattentional blindness attributed to perceptual set whereby people tend to focus their attention on

specific details/feature of a scene

> the likelihood of inattentional blindness increases when people work on task that require a great deal

of attention or that create a heavy perceptual load

- same phenomenon: auditory parallel

Feature Analysis: Assembling Forms

Feature Analysis: process of detecting specific visual inputs and assemble them into a more complex

form


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> e.g: line, edge, corners arranged into triangles, squares etc

> assumes that form perception involves bottom-up processing (individual elements to the whole)

- perceptions are usually created using top-down processing (from the whole to individual elements)

> subject contour phenomenon: perception of contour where none actually exists

- Conclusion: bottom-up and top-down perception have their own niches in form perception

Looking at the Whole Picture: Gestalt Principles

- Gestalt psychology: influential school of thought emerged from Germany during first half 20th century

> Gestalt means form or shape

> prove that: the whole can be greater than the sum of its parts

> no longer active but still influences the study of perception

Example: Phi phenomenon

- illusion of movement created by visual stimuli in rapid succession (seeing smooth motion on: TV)

Gestalt Principles (describes how visual system organizes a scene into a discrete form)

1) Figure and ground

- figure: the thing being looked at

> have more substance and shape, appear closer and seem to stand out in front of the ground

- ground: background against which it stands

2) Proximity

- Things that are closer to one another seem to belong together

3) Closure

- Group elements to create a sense of closure or completeness

4) Similarity

- people tend to group stimuli that are similar

5) Simplicity

- law of Pragnanz (good)

- people tend to group elements that combine into a good figure

- people tend to organize forms in the simplestway possible

6) Continuity

- people tend to follow whatever direction they have been led

Formulating Perceptual Hypotheses

- Understanding problems requires distinguishing between two kinds of stimuli: distal and proximal

- Distal stimuli: stimuli that lie in the distance (in the world, outside the body)

- Proximal stimuli: the stimulus energies that impinge directly on sensory receptors

> images formed by patterns of light falling on retinas

> there are great differences between objects you perceive and the stimulus energies that represent

them


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> distorted, two-dimensional versions of actual, three-dimensional counterpart

- people bridge the gap between distal and proximal stimuli by constantly making and testing

hypotheses about whats out there in the real world (attempting to figure the real shape)

- Perceptual hypothesis is an inference about which distal stimuli could be responsible for the proximal

stimuli sensed

- Ambiguity exists because there isnt enough information to force the perceptual senses to accept the

hypothesis or one of them

Find: proximal and distal stimuli

B)vi) Perceiving Depth or Distance

- Dept perception: interpretation ofvisual cues of how near and far an object is

Binocular Cues

- clues about distance based on the differing views of the two eyes

- principal binocular: based on retinal disparity; object projects images to slightly different locations onthe right and left retinas, so the right and left eyes see slightly different views of the object

- the close an objects gets, the bigger the disparity between the images seen by each eye

- convergence : sensing the eyes coverging toward each other as the focus on the object gets closer

Monocular Cues

- clues about distance based on the perception on one of the eye

- cues about depth from: motion parallax and pictorial depth cues

- motion parallax: images of objects at different distances moving across the retina at different rates

- pictorial depth cues: clues about distance in a flat picture

i) Linear perspective: lights converge in the distanceii) Texture gradient: provides information about depth

iii) Interposition: objects come in between

iv) Relative size: a cue because closer object appears larger

v) Height in plane perspective: distant object appears higher in a picture

vi) Light and shadow

Research:

- Peoples motivational states can skew estimation of distance

- We perceive desirable object closer

Perceptual Constancies in Vision

- stable perception in the face of continually changing sensory input

Function: provide an accurate rendition of distal stimuli based on distorted, ever-changing proximal

stimuli

The Power of Misleading Cues: Optical Cues

- Factors that help perceive world accurately: Gestalt Principle, depth cues, perceptual constancies

- Optical illusion: Inexplicable discrepancies between appearance of a visual stimulus and physical

reality


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- Muller-Lyer

- Impossible figure: objects that can be expressed on 2D but not in 3D

> geometrically inconsistent

Vision for Perception and Vision for Action

Two functions of vision:

1) Vision of Perception (Ventral Stream)

- create an internal representation or model of the external world

> subject of the most research

2) Vision for action (Dorsal stream)

- not concerned with perceiving objects individually but with related process of controlling actions that

are directed to those objects

C) Our Sense of Hearing: The Auditory System

- Distal Stimulus: Sounds heard

- Proximal Stimulus: The sound waves reaching the ears

C)i) The Stimulus: Sound

- Vibration of molecules that travel through a medium at fraction of the speed of the light

- Characterized by: wavelength, amplitude, purity

C)ii) Human Hearing Capacities

- Wavelength: measured in terms of frequency which cycles per second (Hertz)

> the higher the frequency, the higher the pitch

> Human range: 20Hz-20000Hz

Amplitude: measured in decibles

- the higher the amplitude, the louder it is- sound above 85 decibels is dangerous to auditory system

C)iii) Sensory Processing in the Ear

3 sections in human ear: external ear, middle ear, internal ear

External Ear:

- consists of pinna and sound-collecting cone

- depends on the vibration of air molecule

Middle Ear

- consists of ossicles (hammer, anvil, stirrup)

- depends of the vibration of movable bone

Inner Ear

- depends on the waves in a fluid

- consists of cochlea: fluid-filled coiled tunnel that contains reception for hearing

The Flow

1) Sound wave collected by pinna


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2) Then directed along auditory canal (ear canal) to the eardrum

3)Eardrum will vibrate and the vibration will be transferred by ossicles (hammer, anvil and stirrup- they

amplify tiny changes in air pressure)

4) Sounds enter cochlea through the oval window

5) Waves in the fluid of the inner ear stimulate the hair cells

6) Hair cell converts the physical stimulation into neural impulses that are sent to brain

C)iv) Auditory Perception: Theories of Hearing

- About: How sound waves are physiologically translated into perception of pitch, loudness and timbre

>Examine based on the theory of pitch perception (place theory and frequency theory)

Timbre: sound of same note with same pitch played on different instrument. The difference is the

timbre

Place Theory

-Figure: Hermann von Helmholtz

- Specific sound frequencies vibrate specific portion in basilar membrane

> perception of pitch corresponds to the vibration of different portion, or places along the basillar

membrane> this theory holds that specific hair cells at various locations respond independently

> different hair cells are vibrated by different frequencies

Frequency Theory

- perception of pitch depends on the rate of frequency received at which the entire basilar membrane

vibrates

> the whole membrane vibrates in response to sound

Reconciling Place and Frequency Theories

- both theories complement each other

- Flaw in place theory: hair cells dont vibrate independently, but together- True in place theory: wave peaks at particular place depending on the sound frequency

- Low pitch: translated according to place coding

- High pitch: translated according to frequency coding

- Complex pitch: both

C)v) Auditory Localization: Perceiving Sources of Sound

Auditory Localization: Process of locating the source of the sound in space

- Depends mainly on intensity (loudness) and the time at which the sound reaches the ear

- Shadow: partial sound barrier

Music and Its Effects

Figure: neurologist; Oliver Sacks

- Propose that: there is a special connection between music and brain

> musicians areas in brain are larger in the auditory, visuospatial and motor areas of the cerebellum

Figure: Dabiel Levitin

- music is crucial as part of the natural selection process (this is a feature embedded in us naturally)


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Recent research by: Isabelle Peretz and Robert Zatorre

- music training can induce functional and morphological changes in the brain

Additional: William Thompson from UoT

- music training and lessons may facilitate our sensitivity to human emotions reflected in speech

prosody

- speech prosody: musical aspect of speech; intonation (melody) and stress and timing (rhythm)

D) Our Chemical Sense: Taste and Smell

D)i) Taste: The Gustatory System

- a bunch of tastes cells found in the taste bunds that line the trenches around tiny bumps on the tongue

> chemical substance is absorbed through salive and then neural impulses are generated before sending

to thalamus and then cortex (at the frontal lobe)

> have short lives of 10 days and constantly replaced

> new cells are born at the edge of the taste bud before migrating to the centre to die

- four primary tastes: bitter, sweet, sour and salty

- 5th: umami savory taste of glutamate (cheese and meat)> have been indentified to trigger a specific receptors on the tongue

- sensitivity to primary tastes are distributed unevenly but difference in sensitivity are subtle

- perception of taste: depends on complex patterns of neural activity initiated by taste receptors

-innate taste preference varies according to the body nutritional needs and it is learned

- extensive social influence: affects taste preference greatly and varies with different cultures

- nontasters: insensitivity to PTC and PROP

> have 1 quarter per centimeter square as the supertasters

- supertasters: have specialized taste receptors not found in the nontasters

> more sensitive to bitter and sweet substance

- Eating habit: not fond of sweet foods, consume less high-fat foods, react negatively to alcohol and

dont smoke BUT, they respond negatively to vegetable

> supertasters tend to have better health habits than nontasters because of their strong reaction

towards taste

> women are more likely to be supertasters < natural selection process (breastfeed baby)

Perception of flavor

- Flavor: combination of smell, taste and tactile sensation of food in ones mouth

> odours make great contribution in flavor perception

> when odours are absent the ability to detect the taste of food declines noticeably

- these differences in taste sensitivity influences people eating habit

D)ii) Smell: The Olfactory System

- Physical stimuli are chemical substances that dissolved in fluid (mucus) in the nose

> receptors are called olfactory cilia- hairlike structure that is located at the upper nasal

> short life span (30-60 days) and constantly replaced


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- Olfactory receptors have axons that synapse with cells in the olfactory bulb before sending it directly

to the cortex (the only system that doesnt go through thalamus to send information)

-Figures: Linda Buck and Richard Axel

> discovered a gene set consisting of 1000 different genes that affect the operation of our olfactory

receptor cells

> olfactory receptor cells are highly specialized and can detect a limited amount of odor

- sensory adaptation: perceived smell will fade about 4 minutes

> human can distinguish between 10 000 smells but cant name it

-Pheromones: chemical messages, typically imperceptible, that can be sent by one organism and

received by another member of the same species

- Figures: Karlson and Luscher

> they are specific-specific, composed of a single chemical and had specific effect on the organism that

receive them

> better establish in insects

E) Our Sense of Touch: Sensory Systems in the Skin

E)i) Feeling Pressure

- Cells in the nervous system that respond to touch are sensitive to specific patches of skin

> equivalent function to the receptive fields in vision

- if a stimulus is applied continuosly on the same area, the perception of pressure will gradually fade

The Flow

1) the nerve fibers that carry incoming information about tactile stimulation are routed through the

spinal cord to the brainstem2) fibres from each side of the body cross over to the opposite side of the btain

3) the tactile pathway then projects through the thalamus and onto the somatosensory cortex on the

brains parietal lobe

E)ii) Feeling Pain

- crucial for survival

- said as the major factor in the lost of productivity

E)iii) Pathways to the Brain

The Flow:

1) pain messages are transmitted to the brain via two types of pathways that pass through different

parts of thalamus

> fast pathway- registers localized pain and delivers to the cortex within a fraction of a second, usually a

sharp pain, unmyelinated by A-delta fibers

> slow pathway- lags a second or two, usually delivers less-localized, longer-lasting, aching or burning

pain, mediated by unmyelinated neurons dalled C fibers

E)iv) Puzzles in Pain Perception

- perception of pain are greatly influenced by mood, personality, perceptions etc


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- the placebo effect play around with psycho

Figures: Melzack and Wall

- culture does not affect the process of pain perception so much as the willingness to tolerate each type

of pain

Research QuestionsL How does the CNS block incoming pain signals?

- Gate-control theory: incoming pains must pass through a gate in the spinal cord that can be closed,

thus blocking ascending pain signals

> this gate is just a pattern of neural activities that inhibits incoming pain signals

- Melzack: McGill Pain Questionnaire (important in research on pain)

-examined the puzzle of phantom-limb pain

> suggests: endorphine play an important role in the modulation of pain

> other discovery: descending neural pathway that mediates the suppression of pain

> originate from PAG

> neural activities is probably initiated by the endorphine acting on PAG neuron

> These circuit synapses in the spinal cords, where they appear to release more endorphins, thusinhibiting the pain

- in contrast, activation by electrical stimulation can cause analgesic effect

- Newsest discovery: glial cells may contribute the modulation of pain

> 2 types: astrocytes and microglia (role in chronic pain)

> significance: development of new drugs for treating chronic pain

F) Our Other Senses

F)i) The Kinesthetics System

- monitor the position of the various parts of the body

F)ii) The Vestibular System

- respond to the gravity keeps human informed of bodys location in space

> provide the sense of balance, equilibrium, compensating forchanges in the bodys position

- share space in the inner ear with the auditory system

- semicircular canal: make up the largest part of vesti system

psyc 100 ch. 4 textbook notes

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