sensation chapter 5. sensation sensation our senses receive information from our world perception...
TRANSCRIPT
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Sensation
Chapter 5
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Sensation
SensationOur senses receive information from our world
PerceptionHow we take this information and organize/interpret it
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Sensation
Bottom-Up Processing analysis that begins with the sense
receptors and works up to the brain’s integration of sensory information
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Sensation- Thresholds Our awareness of faint sensations: Absolute Threshold
minimum stimulation needed to detect a particular stimulus 50% of the time
Ex: test hearing with various sounds of different pitches; point where ½ the time you hear a pitch and ½ the time you don’t
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Sensation- Thresholds Sensation also depends on other
factors: Signal Detection Theory
predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise)
detection depends partly on person’s experience expectations motivation level of fatigue
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Sensation- Thresholds
Subliminal (“below threshold”)
When stimuli are below one’s absolute threshold for conscious awareness
May influence but not have enduring, powerful effects Ex: positive/negative pictures; instructor’s
scowl
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Sensation- Thresholds
Need to be able to detect among different sensations
Difference Threshold minimum difference between two stimuli required for
detection 50% of the time
Weber’s Law-to perceive difference, two stimuli must differ by a constant minimum percentage (not constant/same amount)
light intensity- 8% weight- 2% tone frequency- 0.3%
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Sensation - Adaptation
Sensory adaptation- diminished sensitivity as a consequence of constant stimulation As length of exposure increases, nerve
cells fire less often Ex: pool, wristwatch
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Vision
Transduction conversion of one form of energy
to another in sensation, transforming of
stimulus energies into neural impulses
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Vision
Hue dimension of color determined by
wavelength of light Intensity
amount of energy in a wave determined by amplitude brightness loudness
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Vision- Physical Properties of Waves
Short wavelength=high frequency(bluish colors, high-pitched sounds)
Long wavelength=low frequency(reddish colors, low-pitched sounds)
Great amplitude(bright colors, loud sounds)
Small amplitude(dull colors, soft sounds)
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Vision
Pupil- adjustable opening in the center of the eye
Iris- a ring of muscle that forms the colored portion of the eye around the pupil and controls the size of the pupil opening
Lens- transparent structure behind pupil that changes shape to focus images on the retina
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Vision
Accommodation- the process by which the eye’s lens changes shape to help focus near or far objects on the retina
Retina- the light-sensitive inner surface of the eye, containing receptor rods and cones plus layers of neurons that begin the processing of visual information
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Vision
Acuity- the sharpness of vision Nearsightedness- condition in which
nearby objects are seen more clearly than distant objects because distant objects in front of retina
Farsightedness- condition in which faraway objects are seen more clearly than near objects because the image of near objects is focused behind retina
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Retina’s Reaction to Light- Receptors
Rods peripheral retina detect black, white and gray twilight or low light
Cones near center of retina fine detail and color vision daylight or well-lit conditions
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Retina’s Reaction to Light
Optic nerve- nerve that carries neural impulses from the eye to the brain
Blind Spot- point at which the optic nerve leaves the eye, creating a “blind spot” because there are no receptor cells located there
Fovea- central point in the retina, around which the eye’s cones cluster
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Vision- Receptors
Receptors in the Human Eye
Cones Rods
Number
Location in retina
Sensitivity in dim light
Color sensitive? Yes
Low
Center
6 million
No
High
Periphery
120 million
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Visual Information Processing
Feature Detectors nerve cells in the
brain that respond to specific features
shape angle movement
Stimulus
Cell’s responses
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Visual Information Processing
Parallel Processing simultaneous processing of several
aspects of a problem simultaneously
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Visual Information Processing
Trichromatic (three color) Theory Young and Helmholtz three different retinal color receptors
red green blue
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Visual Information Processing
Opponent-Process Theory- opposing retinal processes enable color vision
“ON” “OFF”red greengreen red blue yellow yellow blue black whitewhite black
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Color-Deficient Vision
People who suffer red-green blindness have trouble perceiving the number within the design
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Audition-Hearing Loudness
strength of sound waves (height)
Pitch a tone’s highness or lowness depends on Frequency
Frequency the number of complete wavelengths that
pass a point in a given time
Wavelength the distance from the peak of one wave to
the peak of the next
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Waves
Short wavelength=high frequencyhigh-pitched sounds)
Long wavelength=low frequencylow-pitched sounds)
Great amplitude(loud sounds)
Small amplitude(soft sounds)
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Audition- The Ear Outer Ear
Ear appendage, Auditory Canal Middle Ear
chamber between eardrum and cochlea containing three tiny bones (hammer, anvil, stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window
Inner Ear innermost part of the ear, contining the
cochlea, semicurcular canals, and vestibular sacs
Cochlea coiled, bony, fluid-filled tube in the inner ear
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How We Detect Pitch
Place Theory (high) the theory that links the pitch we hear with
the place where the cochlea’s membrane is stimulated
Frequency Theory (low) the theory that the rate of nerve impulses
traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch
200 waves p.s. / 200 nerve impulses p.s.
Combination (intermediate)
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How We Locate Sounds
Compare responses of 2 ears: Intensity
Arrival time
We then compute the location
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Audition
Conduction Hearing Loss hearing loss caused by damage to the
eardrum, bones of middle ear that conduct sound waves to the cochlea
Hearing Aid Nerve Hearing Loss
hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerve
Cochlear Implant
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Touch
Skin Sensations pressure
only skin sensation with identifiable receptors
warmth cold pain
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Pain Gate-Control Theory
theory that the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brain
“gate” opened by the activity of pain signals traveling up small nerve fibers
“gate” closed by activity in larger fibers or by information coming from the brain
Ex: distract from pain: needle/surgery patients
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Taste Taste Sensations
sweet sour salty Bitter Umami (Japanese) – meaty taste (glutamate)
Taste Adaptation Fatigue of receptors sensitive to certain
tastes Sensory Interaction
the principle that one sense may influence another as when the smell/sight of food influences its taste
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Smell
Molecules in air
•go into nasal cavity
•reach receptor cells
•send messages to olfactory bulb
•cortex/temporal lobe
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Body Position and Movement
Kinesthesis the system for sensing the position and
movement of individual body parts Know current/changing positions of body parts
Vestibular Sense the sense of body movement and position Monitors head’s movement & position including the sense of balance
When twirl around & stop, fluid in ear does not reach neutral state