Download chapter 5: sensation and reality

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CHAPTER 5:
SENSATION AND REALITY
I.
General Properties of Sensory Systems
A. Vocabulary
1. data reduction system – any system that selects, analyzes, or condenses
information; selects, analyzes, and filters information until only important
details remain; boils down floods of information into a stream of useful
data.
2. transducer – a device that converts energy from one system into energy in
another.
3. sensory analysis – separation of sensory information into important
elements (part of selects).
4. perceptual features – basic elements of a stimulus, such as lines, shapes,
edges, or colors (part of selects).
5. feature detector – a sensory system highly attuned to a specific stimulus
pattern (frog needs moving stimuli) (part of analysis).
6. sensory coding – codes used by the sense organs to transmit information to
the brain (part of the coding)
7. phosphenes – visual sensations caused by mechanical stimulation of the
retina; (caused by pressure).
8. sensory localization – principle that the type of sensation experienced is
related to the area of the brain activated; some brain areas receive visual
information, others auditory information, etc.
9. sensation – immediate response in the brain caused by excitation of a
sensory organ.
10. perception – when the brain organizes sensations into meaningful patterns.
II.
Psychophysics: study of the relationship between physical stimuli and the
sensations they evoke in a human observer.
A. Vocabulary
1. absolute threshold – the absolute minimum amount of physical energy
necessary to produce a sensation.
B. Difference Thresholds – a change in stimulus intensity that is detectable to an
observer.
1. JND – Just Noticeable Difference: any noticeable difference in a stimulus.
2. Weber’s law: the JND is a constant proportion of the original stimulus
intensity. Ex. In taste, need about 1/5 more, i.e., 5 tsp. sugar, need to add
1 more to notice the difference.
C. Perceptual Defense and Subliminal Perception
1. perceptual defense- resistance to perceiving threatening or disturbing
stimuli; MeGinnies, 1949 research of “clean’” vs. “dirty” words.
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2. subliminal perception – perception of a stimulus below the threshold for
conscious recognition; normal limen (threshold or limit for awareness);
found some emotional impact in a study of positive vs. negative images
flashed too briefly to be recognized; however, it altered the impressions
students formed of a target person.
3. Subliminal persuasion – studies found only weak impact; little evidence
that subliminal messages can persuade/greatly influences our behavior.
III.
Vision
A. Vocabulary
1. visible spectrum – part of the electromagnetic spectrum to which the eyes
are sensitive.
2. hue – classification of colors into basic categories of red, orange, yellow,
green, blue, indigo, and violent.
3. saturation – the degree of a color’s purity.
4. brightness – the intensity of lights or colors.
B. Structure of the Eye
1. lens – structure in the eye that focuses light rays; makes “fine-tuning”
2. retina – the light-sensitive layer of cells at the back of the eye.
3. cornea – transparent membrane covering the front of the eye; bends light
inward, i.e., focusing.
4. accommodation – changes in the shape of the lens of the eye via tiny
muscles.
C. Visual Problems
1. hyperopia – difficulty focusing nearby objects (farsightedness); eye too
short.
2. myopia – difficulty focusing distant objects (nearsightedness); eye too
long.
3. astigmatism – defects in the cornea, lens, or eye that cause some areas of
vision to be out of focus.
4. presbyopia – farsightedness caused by aging.
D. Light Control
1. iris – circular muscle that controls the amount of light entering the eye.
2. pupil – the opening at the front of the eye through which light passes.
3. cones – visual receptors for colors and daylight visual acuity.
4. rods – visual receptors for dim light that produce only black and white
sensations.
5. blind spot – an area of the retina lacking visual receptors.
E. How the Brain Sees the World – the brain seems to first analyze information
into lines, angles, shading, movement, and other basic features, then other
brain areas combines these features into meaningful visual experiences.
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F. Visual Acuity – sharpness of visual perception.
1. fovea – an area at the center of the retina containing only cones.
G. Peripheral Vision – vision at the edges of the visual field; rods are quite
sensitive to movement; important for sports, driving, etc.
1. tunnel vision – vision restricted to the center of the visual field.
IV.
Color Vision
A. Color Theories
1. cones most sensitive to yellowish green and appear brightness.
2. rods most sensitive to blue-green
3. trichromatic theory – theory of color vision based on three cone types: red,
green, and blue; others are based on combination of these three; and black
and white sensations are produced by rods. But why not reddish green
light or yellowish blue? Or the primary colors themselves?
4. opponent-process theory – theory of color vision based on three coding
systems (red or green, yellow or blue, black or white); states that vision
analyzes colors into “either-or” messages.
5. Right?? - belief that the trichromatic theory operates within the eye (what
happens in the eye) and the opponent-process theory occurs as the
information is being sent to the occipital lobe, (how colors are analyzed)
in the optic pathway.
6. afterimage – visual sensation that persists after a stimulus is removed.
7. visual pigments – light-sensitive chemicals found in the rod and cones;
three types of cones fire nerve impulses at different rates to produce
various color sensations.
8. simultaneous color contrast – changes in perceived hue that occur when a
colored stimulus is displayed on backgrounds of various colors; color
experiences are actively constructed in the brain vs. simply receiving
prepackaged color messages.
B. Color Blindness and Color Weakness
1. color blindness – a total inability to perceive colors; either lacks cones or
the cones don’t function properly; rare.
2. color weakness – an inability to distinguish some colors; about 8% of
males & about 1% of females.
3. Ishihara test – a test for color blindness and color weakness.
V.
Dark Adaptation – increased retinal sensitivity to light.
A. Vocabulary
1. rhodopsin – the light-sensitive pigment in the rods, when stuck by light
visual pigments bleach/break down chemically and need to recombine to
restore light sensitivity; night vision is due mainly to an increase in
rhodopsin in the rods at night; takes about 30/35 minutes to completely
adapt.
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2. retinal – part of the chemical compound that makes up rhodopsin
(retinene).
2. night blindness – blindness under conditions of low illumination.
VI.
Hearing – if you throw a stone into a quiet pond, a circle of waves will spread in
all directions, sound travels the same ways as a series of invisible waves of
compression (peaks) and rarefaction (valleys) in the air.
A. Vocabulary
1. pitch – higher or lower tones; related to the frequency of sound waves.
2. loudness – intensity of a sound; determined by the amplitude of sound
waves.
B. Mechanisms of Hearing – how are sounds converted to nerve impulses?
1. pinna – visible external part of the ear; acts like a funnel to concentrate
sounds.
2. typanic membrane – the eardrum; its motion causes the auditory ossicles
to vibrate.
3. auditory ossicles – 3 small bones that link the eardrum to the cochlea; they
are the malleus, incus, and stapes.
4. oval window – membrane on the cochlea connected to the 3rd auditory
ossicle (stapes).
5. cochlea – snail-shaped organ that makes up the inner ear.
6. Organ of Corti – center part of the cochlea, containing hair cells, canals,
and membranes.
7. hair cells – receptor cells within the cochlea that transduce vibrations into
nerve impulses.
8. stereocilia – bristle-like structures on hair cells.
9. The Process: as the stapes moves the oval window, the round window
bulges outward, allowing waves to ripple through fluid in the cochlea.
The waves move membranes near the hair cells, causing cilia/bristles on
the tips of the cells to bend. The hair cells then generate nerve impulses
carried to the brain.
10. frequency theory – holds that tones up to 4,000 hertz are converted to
nerve impulses that match the frequency of each tone.
11. place theory – theory that higher and lower tones excite specific areas of
the cochlea.
C. Deafness
1. conduction deafness – poor transfer of sounds from the eardrum to the
inner ear.
2. nerve deafness – deafness caused by damage to the hair cells or auditory
nerve; hearing aids don’t work because auditory messages are blocked
from reaching the brain.
3. cochlear implant – bypass hair cells and stimulate the auditory nerves
directly.
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4. stimulation deafness – damage caused by exposing the hair cells to
excessively loud sounds.
5. temporary threshold shift – temporary, partial loss of hearing
6. tinnitus – ringing/buzzing sensation in the ears.
VII.
Smell and Taste – the two chemical senses; respond to chemical molecules.
A. Sense of Smell – Olfaction
1. anosmia – loss or impairment of the sense of smell.
2. lock and key theory – holds that odors are related to the shapes of
chemical molecules.
3. pheromone – an airborne chemical signal.
4. vomeronasal – a sensory organ sensitive to pheromones in animals.
5. olfactory bulb
B. Taste
1. taste bud – receptor organ for taste; located on the top side of the tongue,
especially around the edges; based upon lock-and-key matches between
molecules and intricately shaped receptors.
VIII.
Somesthetic Senses – sensations produced by the skin, muscles, joints, viscera,
and organs of balance.
A. Skin senses – the senses of touch, pressure, pain and cold.
1. skin receptors – sensory organs for touch, pressure, pain, cold, and
warmth.
B. Pain
2. phantom limb – the illusory sensation that a limb still exists after it is lost
through accident or amputation.
3. visceral pain – pain originating in the internal organs.
4. referred pain – pain that is felt in one part of the body but comes from
another.
5. somatic pain – pain from the skin, muscles, joints, and tendons; from large
nerve fibers and act as the body’s warning system.
6. warning system – pain based on large nerve fibers; warns that bodily
damage may be occurring.
7. reminding system – pain based on small nerve fibers; reminds the brain
that the body has been injured.
C. Dynamic touch – touch experienced when the body is in motion; a
combination of sensations from skin receptors, muscles, and joints; makes it
possible for us to use a wide range of tools, utensils and objects as if they
were extensions of our bodies.
D. Kinesthetic senses – senses of body movement and positioning; muscles and
joints that detect body position and movement.
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E. Vestibular senses – senses of balance, position in space, and acceleration;
receptors in the inner ear for balance, gravity, and acceleration.
1. otolith organs – vestibular structures sensitive to movement, acceleration,
and gravity; stimulates hair-like receptor cells.
2. semicircular canals – fluid-filled canals containing the sensory organs for
balance.
3. crista – floating structure that responds to fluid movement within the
semicircular canals; head motion causes the bending of the crista
stimulates hair cells and signals head rotation.
4. ampulla – enlarged area in a semicircular canal containing the crista.
5. sensory conflict theory – explains motion sickness as the result of a
mismatch between information from vision, the vestibular system, and
kinesthesia.
IX.
Adaptation, Attention, and Gating
A. Sensory Adaptation – decrease in sensory response to an unchanging stimulus;
olfactory receptors adapt that fastest.
B. Physiological nystagmus – involuntary tremor of the eye; too small to be seen,
the movements shift visual images from one receptor cell to another (prevents
sensory adaptation).
C. Selective Attention – voluntarily focusing on a specific sensory input.
D. Sensory Gating – alteration of sensory messages in the spinal cord; refers to
facilitating or blocking sensory messages in the spinal cord.
1. gate control theory – proposes that pain messages pass through neural
“gates” in the spinal cord; can “close” the gate by sending a pain message
and other pain messages may not be able to pass through.
2. acupuncture – Chinese medical art of relieving pain and illness by
inserting thin needles into the body.
3. beta-endorphin – a natural, painkilling brain chemical similar to morphine.