Chapter 5: Sensation & Perception Flashcards
Transduction
process by which sensory stimuli are converte to neural signals
Sensation
stimulation of sense organs; absorption of energy by sensory organs
Perception
selection, organization, and interpretation of sensory information;
organization and translation of sensory information into something meaningful
Physical property of light and related perception
wavelength/frequency
hue (colour)
Physical property of light and related perception
Amplitude
brightness
Physical property of light and related perception
purity
saturation
Timbre
purity of sound;
pure tone that has only one frequency and one amplitude
Blindspot
nerves run from retina to brain converge in one spot where no receptor cells are present; image falling on this spot cannot be seen
Receptor cells
- in the retina’s innermost layer
- sensitive to light
- rods > cones
Fovea
tiny spot in the center of the retina that only contains cones; rods outnumber cones in the periphery of the retina
Cones
colour vision
daylight vision
visual acuity
3 pigments
receptor cells
Rods
peripheral vision
night vision
one pigment
receptor cells
Processing of visual information in the brain
Where: thalamus, occipital lobe, parietal lobe, temporal lobe
What: perception of brightness, orientation, form, colour, motion, & depth
Processing visual information in the retina
Where: receptive field of ganglion cell
What: perception of light/dark contrast or simple geometric shapes
Center-surround antagonism
property of the receptive field of a ganglion cell
Feature of the center of receptive field
excitatory; rate of firing a nerve impulse increases when light falls on the center
Feature of the surrounding of receptive field
inhibitory; rate of firing nerve impulse decreases when light falls on the surrounding area
Information processing in the brain
Thalamus
perception of brightness
Information processing in the brain
Primary visual cortext in occipital lobe
perception of orientation
Information processing in the brain
Inferior temporal lobe
perception of form and colour
Information processing in the brain
Parietal lobe
perception of motion and depth
Damage to the occipital lobe will result in a condition called:
blindsight
Steps
Cat experiment by Hubel and Wiesel
- cat was shown a line in various orientation
- microelectrode was placed in cat’s primary visual cortex
- APs from individual neurons were recorded by oscilloscope
Findings
Cat experiment by Hubel and Wiesel
- vertical line elicited rapid firing rate;
- horizontal line elicited no response (firing rate at baseline measure);
- tilted line elicited moderate firing rate
Conclusion
Cat experiment by Hubel and Wiesel
- neurons are highly specialized; they respond to very specific stimuli
Ventral Stream
- leads to temporal lobe
- processes details of “what” objects are out there - the “what” pathway
after visual information is processed in the primary visual cortex it is sent to two other cortical areas for further processing
Agnosia
- individual suffers from agnosia when the ventral stream is damaged
- there are multiple forms: visual-form agnosia, colour agnosia, face agnosia
know DF
Visual-form agnosia
inability to recognize visual forms or familiar objects
Colour agnosia
inability to recognize colours
face agnosia
inability to recognize faces
Dorsal stream
- leads to parietal lobe
- processes the details of “where” objects are n “how” to interact with them - the “where” or “how” pathway
- vision for action pathway
- when damaged, individual cannot guide bodily movements based on visual information
know LM, RV, DF
after visual information is processed in the primary visual cortex it is sent to two other cortical areas for further processing
Color
psychological representation of a mixture of lights in different wavelengths
Subtractive colour mixing
stars with light (white)
colored filters between viewer and light source subtract wavelengths from the light, giving it colour
subtractive = mixing pigments
middle is black
Additive color mixing
starts without light (black)
light sources of various wavelengths combine to form colors
additive = mixing lights
middle is white
Trichromatic theory of colour vision
Weakness?
- human eye has three types of receptors with differing sensitivities to different light wavelengths
- light of diff wavelengths stimulates three diff types of cone receptors in diff ways
- ratio of activity of these 3 receptors creates our impression of different colors
fails to explain complementary afterimage
Opponent process theory of color vision
color perception depends on receptors that make antagonistic responses to three pairs of colors
- opponent-process cells are inhibited by a color and have a burst of activity when it is removed
Color Blindness
someone who is born with only one or two cone receptors
- person unable to create colors depending on the type of receptor missing
- most common deficiency is red or green
- two receptors missing = no color
Psychophysics
study of how physcial stimuli are related or translated into psychological experience
- relationship can be modelled by Weber’s law and Fechner’s law
Absolute Treshold
min amount of stimulation that an organism can detect
- intensity level at which probability of detection is 50%
- researchers found that there is no single stimulus intensity at which subject jumps from no detection to completely accurate detection (unlike neurons)
- change of detecting stimulus increases gradually as stimulus intensity is increased
Signal Detection Theory
detection of stimulus depends on:
1. intensity
2. psychological state of the individual or context of the situation
two processes are involved:
1. sensory process
2. decision making process
3 types of responses to decision outcomes for preceiver’s response vs. stimulus
1. unbiased responses
hit rate = correct rejection rate (95%); miss rate = false alarm rate (5%)
2. biased responses: YEA sayers
high hit rate & high false alarm rate
3. biased responses: NAY sayers
high correct rejection rate and high miss rate
Just Noticeable Difference (JND)
smallest difference in the amount of stimulation that a specific sense can detect
Weber’s Law
size of JND is a constant proportion of the size of initial stimulus
△I/I = K
- constant increments in stimulus intensity prouce smaller and smaller increases in precieve magnitude of sensation
Fechner’s Law
subjective senstation is proportional to the log of intensity of stimulus
S = k log R
implication: psychological reality correlates with a physical reality - psychophysical parallelism
Psycho = Physical
k = constant
S = senstation (measured in JND)
R = Reiz (stimulus)
Factors that affect the outcome of perception
clarity of stimulus
context
way of presentation
viewing percpective
background knowledge of viewer
focus of attention
schema
etc.
Bottom-up processing
perception based on the physical features of the stimulus
Data-driven processing
Top-down processing
interpretation of sensory information based on knowledge, expectations, and past experience
concept-driven processing
Two systems of thoughts
Structuralism
breaks down whole into its parts
method: introspection
Two systems of thoughts
Gestalt Psychology
whole is more than the sum of its parts
- integrating elementary components to form a whole - opposite of structuralism
- a form of top-down/conceptually driven processing
Principle of Closure
people may complete figures that actually have gaps in them
Principle of Continuity
people tend to connect points that result in a straight or gently curve lines that create smooth patterns
Principle of Similarity
people tend to group items that are similar in color, shape, brightness, etc. to form a unit
Principle of Proximity
things that are close to one another seem to belon together
- they form a unit
Principle of figure-ground
figure is more “thing-like” and more memorable than the ground
