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Sense
translates info from outside nervous system into neural activity giving nervous system knowledge of the world (initial message, not interpretation)
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operation of sensory systems
- 1. accessory structures
- 2. transduction
- 3. info relayed to thalamus
- 4. thalamus reroutes to appropriate place
- 5. interpretation of stimulus
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accessory structures (ear, lens in eye)
captures and modifies stimulus energy
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transduction
process that transforms physical energy into electrochemical signals (done w/ receptors)
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thalamus
relay station for pain and sense-organ signals
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detection threshold
smallest amount of energy required for person to report a stimulus on half of the trials
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signal detection
assesses persons sensitivity to stimulus and criterion for saying they detect a stimulus
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Weber's law
difference threshold proportional to intensity of the stimulus
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difference threshold
point at which pair of stimuli are recognized as being different half of the time
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coding
translation of physical properties of stimulus into a unique pattern of neural activity (specifically identifies particular physical properties)
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feature detectors
code physical properties of stimuli by responding to very specific features located in a more complex stimulus (responds to a unique code)
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Cornea
transparent bulge on the front of eye (light enters here)
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Pupil
an opening in the iris (light passes through pupil)
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Iris
muscular disk controls amount of light entering eye
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Lens
elastic membrane capsule
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Thin lens
focus on distant objects
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Thicker lens
focus on nearby objects
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Nearsightedness
- difficulty focusing on distant objects
- eyeball is too long and so focuses light rays in front of the retina
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Farsightedness
- difficulty focusing clearly on near objects
- eyeball is too short and so light rays focus behind the retina
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Retina
- multilayered tissue located at rear of eyeball
- contains photoreceptors
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Photoreceptors
- specialized nerve cells
- convert light energy into neural responses
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Rods
black and white receptors - function best in dim light
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Cones
color receptors - function best in bright light
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Optic nerve
carries neural signals to thalamus and then occipital lobe
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color is the result of
light from different mixtures of wavelengths
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Theories of Color Vision
- Trichromatic
- Dual process theory
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Trichromatic (Young-Helmholtz)
any color can be matched by mixing lights of 3 wavelengths: blue, green and red (3 types of color receptors in retina)
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Dual process theory
- color processing occurs in 2 stages
- 1. retina's red/green/blue cones respond in varying degrees to light wavelengths
- 2. ganglion cells combine output of cones into red-green, blue-yellow, and black-white information
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Color deficiency
- Red or green sensitive cones done function properly
- vision is dichromatic instead of trichromatic
- difficut to distinguish red and green
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perception
process of how sensations are interpreted as meaningful experiences (compares w/ previous info)
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3 types of processing
- bottom-up
- feature
- top down
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Bottom up processing
taking individual elements of stimulus and combining into unified whole
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feature detectors
respond to selected, basic features of a stimulus - features recombined to create the perceptual whole
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Top down processing
sensory information is interpreted in light of existing knowledge, ideas, and expectiation (prior experiences)
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Figure-ground
organize stimuli into a foreground figure and a background
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grouping
- tend to perceive objects as groups rather than individual units:
- proximity - nearness
- similarity - likeness
- closure - incomplete figures as complete
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Size and shape constancy
perceived size/shape of objects remain same despite changes retinal image
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linear perspective
parallel lines that are distant appear to converge toward a point on the horizon
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relative size
distant object appears smaller than does same object close up
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How do we perceive objects as 3D when retinal image is 2D
depth cues
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stroboscopic motion
perception of motion from series of "snapshot" images - each slightly different from previous one
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Phi phenomenon
series of lights flas on and off sequentially at alightly different locations - "moving light"
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ability to experience environmental stimuli
sensation
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we receive info from our environment through
vision, hearing, taste, touch, and smell
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specialized nerve cells that detect stimuli in environment and are responsible for transduction
sensory receptors
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sensory receptors for smell
olfactory receptors
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our formed disposition based on our life experiences
perceptual set (schema)
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what influences your perception
what you are expecting
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the ability to attend to the things that are of interest to us by filtering stimuli
selective attention
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