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Chapter 4

PSY 101LEC Chapter Notes - Chapter 4: Color Vision, Peripheral Vision, Sensory Neuron


Department
Psychology
Course Code
PSY 101LEC
Professor
Wendy Quinton
Chapter
4

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Chapter
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4
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Sensation
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and
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Perception
Sensation: stimulation of sense organs
                       involves the the absorption of energy (light or sound waves)
Process: 1) Sensory receptors detect stimuli
                 2) Sensory stimuli are transduced into electrical impulses
                 3) Electrical impulses move along the neural pathways to brain.
                 4) Impulses are decoded into information
Perception: selection, organization, interpretation of sensory input
                         involves categorizing and translating
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Visual agnosia---inability recognize object through sight
Vision---physical stimulus: light (electromagnetic radiation)
Physical
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properties
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of
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light
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------
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Related
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perception
Wavelength                                      Hue (color)
Amplitude                                        Brightness
Purity                                                Saturation (color richness)
Visual system
Light → Cornea (transparent outer layer; allows light come in) → Pupil (regulate amount of
light)→ Lens (accommodation:adjust its curvature to alter visual focus) → Retina (light-sensitive,
with an upside down reflected image)
Importance
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of
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Retina:
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absorbs light, processes image, sends visual information to the brain
                                           where the visual receptors are located to detect light
● Rods: night vision & peripheral vision
● Cones: daylight vision & color vision
Blind
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spot:
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can not see the image that falls on optic disk
Visual problems
● Nearsightedness: close objects clear + distant objects  blurry
                                      focus of light from distant objects falls a little short of the retina
                                      causes--- the cornea or lens bends light too much; eyeball is too long.
● Farsightedness: distant objects clear + close  objects blurry
                                   the focus of light from close objects falls behind the retina
                                   causes---eyeball is too short
● Cataract: clouded lens (the older)
Visual adaptation
dark adaptation---sensitive to light in low illumination
light adaptation---sensitive to light in high illumination
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Connection with brain
Neural signals → Bipolar & Ganglion Cells (integrate,compress signals)→ Optic Nerve (axons
that connect eyes and brain)→ Optic Disk (hole for axons to depart) → Optic Chiasm (point where
axons from half of each eye project opposite half of brain)→ Thalamus (lateral geniculate nucleus)
→Primary Visual Cortex (in occipital lobe)→ Other Cortical Areas (where pathway-dorsal
stream + what pathway-ventral stream)
Color perception
Color mixture    Subtractive color---removing some wavelengths of light, leaving less light
                               Additive color---putting more light in the mixture than any one light
Trichromatic theory: eye has three groups of receptors sensitive to wavelengths associated with
red, green, and blue
Opponent process theory: receptors make antagonistic responses to three pairs of colors
Visual perception---influenced by expectation
A perceptual set—a readiness to perceive a stimulus in a particular way
△The same visual input can result in radically different perception.  (subjective)
Inattentional blindness: focus on a specific feature of the scene instead of the whole
Form perception: recognition of objects
It involves---feature analysis (assembly a more complex form based on specific elements)
Top-down processing
Bottom-up processing
A progression from the whole to elements
A progression from individual elements to the whole
Gestalt principles: whole is greater than sum of parts (unified whole)
“form” “shape”----Ex. Phi Phenomenon:  illusion of movement in rapid succession
● Figure and Ground: “figure”---object           “ground”---background
                                           divide visual displays into figure and ground (perceptional switch)
● Proximity---close elements group together
● Closure---supply missing elements to close or complete a familiar figure.
● Similarity---similar elements group together
● Simplicity---organize elements in the simplest way
● Continuity---  see elements in ways that produce smooth continuation.
Perceptual hypothesis: inference about what form could be responsible for a pattern of sensory
stimulation
Perceptual constancy: tendency to experience a stable perception in the face of continually
changing sensory input
Depth perception---visual cues that indicate how near or far away objects are
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