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