PSY100H1 Lecture Notes - Two-Streams Hypothesis, Contrast Effect, Additive Color
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Published on 30 Jan 2013
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Sensation- involves detection of external stimuli, responses to those stimuli, transmission of responses to the
brain
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Sensation about going to world to the brain
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Transduction- process by which sensory receptors pass impulses to connecting neurons when they receive
stimulation
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Stimuli need to be translated into chemical or electrical signals to be understood
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Information route: thalamus-> cortex
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Perception- involves the processing, organization, and interpretation of sensory signals in the brain, which results
in an internal representation of the stimuli- and conscious experience of it
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Everything experienced in brain
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World is entirely constructed by you
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Context is important
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Change is important
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Important:
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Absolute threshold- the minimum intensity of stimulation that must occur before you experience a sensation
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Difference threshold- just noticeable difference between two stimuli (minimum amount of change)
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As intensity increases, larger difference threshold
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Signal Detection Theory- Determining whether you notice a faint stimulus or not requires you to make a
judgement based on ambiguous information
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Hit- stimulus on, response yes
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Miss- stimulus on, response no
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False alarm- stimulus off, response yes
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Correct rejection- stimulus off, response no
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Response bias- person's tendency to report detecting a signal in an ambiguous trial
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Sensory adaptation- if stimulus is constant, humans stop responding to it (decreasing sensitivity to constant
stimuli)
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Stimuli for taste- chemical substances from food dissolved in saliva
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Taste receptors- (in taste buds) send signals to brain -> produces experience of taste
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Sweet
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Salty
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Sour
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Bitter
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Umami (savory)
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Taste experience composed of:
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Smell and texture also important- TASTE EXPERIENCE OCCURS IN BRAIN!
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Stimuli for smell- chemical substances from outside the body that dissolve in fluid on mucous membranes in nose
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Olfactory epithelium0 thin layer of tissue embedded with smell receptors transmits info to olfactory bulb (brain
center for smell)
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Good at discrimination, but not at naming specific odors
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Temperature receptors
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Haptic receptors- for pressure
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2 types of pain receptors
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Somatosensory cortex-- responds to sensory information
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Nerve signals -> thalamus -> primary stomasensory cortex in parietal lobe
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Phantom limb pain- experience occurs in brain, so people may still experienced pain
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2 kinds of pain receptors:
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Fat myelinated fibers- sharp, immediate pain (protection)
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Slow, nonmyelinated fibers- dull steady pain (recuperation)
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Pain is a perceptual experience
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Gate control theory of pain- For pain to be experienced, pain receptors must be activated; neural gate in spinal
cord must signals through to the brain
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Distractions, larger haptic nerve fibers, can close neural gate
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Touch
Have blind spots, usually goes unnoticed
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Accommodation- muscles change shape of lens, flattening an focus on objects
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Photoreceptors- converts energy from light particles (photons) into chemical reaction that produces electrical
signal
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Dorsal stream- specialized for spatial perception, spatial relations
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Ventral stream- specialized for perception and recognition
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Object agnosia- when ventral stream is damaged, patient cannot recognize what an object is
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Every neuron has particular receptive field- particular type of stimulus for which that neuron preferentially
responds
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Receptive fields more complex higher in the visual system
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Lateral inhibition- visual process in which adjacent photoreceptors tend to inhibit one another
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Contours/ edges important to be able to see
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Thought to also be responsible for simultaneous contrast illusion
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S(short wavelengths)- blue
M(medium wavelengths)- green
L(Long wavelengths)- red
Cones:
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Perception of color determined by ratio of activity among three receptors
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Additive color mixing
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Subtractive color mixing
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Color Perception
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Proximity- the closer two figures are, most likely to grouping themselves together
Similarity- tend to group things together depending on how similar they are
Good continuation- tend to interpret intersecting lines as continuous rather than as changing direction
radically
Closure- tend to complete figures that have gaps
Illusory contours- tend to perceive contours, even when they do not exist
Gestalt principles of perceptual organization
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CONTEXT!
Object Perception
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Vision
Ch.5 Sensation vs. Perception
January-28-13
6:15 PM
PSY100H1 Page 1