PSYCH 100 Lecture Notes - Lecture 5: Retina, Action Potential, Hot Tub

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Sensation vs. Perception
I.
Psychophysics
II.
Vision
III.
Audition
IV.
Experiencing events - 2 stages
Stage 1 - Sensation
Converting the physical world into a mental representation
(transduction)
Ex. Variations of light ---> experience of color
Ex. Variations of air pressure ---> experience of sound
Relaying that information to the brain (conduction)
Stage 2 - Perception
Select, organize and interpret these mental representations
Ex. We can recognize the color green
Ex. We can distinguish Bach from Bruno Mars
Psychophysics
The study of the relationship between physical characteristics of stimuli
(energy) and our psychological experience of them
Ex. Light ---> brightness, sound ---> volume, pressure ---> weight,
taste ---> sweetness/bitterness
Absolute thresholds: smallest magnitude of a stimulus that can be reliably
discriminated from NO stimulus at least 50% of the time
Difference threshold: minimum difference between 2 stimuli that a person
can detect at least 50% of the time (JUST noticeable difference)
Signal detection theory: predicts how and when we will detect the presence
of a stimulus amidst background stimulation
Complex decision mechanisms are involved to determine if a stimulus
exists
Based on…
Stimulus strength
Our experiences - expectations, motivation, level of fatigue
Ex. Sounds in my house vs. sounds outside (expected a
murdered vs. it's just background noise)
®
Absolute thresholds and difference thresholds are NOT fixed
Our sensitivity to a stimulus varies based on experiences
§
Factors affecting Absolute and Difference thresholds
Chance variation - noise in the system influences sensitivity
§
Stimulus intensity
Weber's law - the greater the intensity of a stimulus, the larger
the difference must be to detect a difference
Must differ by a constant proportion
®
§
Sensory adaptation - our sensitivity to an unchanging stimulus
diminishes
Ex. First getting into a hot tub vs. getting used to the heat, want it
to be hotter when the temp. hasn't changed
§
Vision
Q: how do we turn light energy (light waves - physical stimulus) into vision
(psychological experience)
2 aspects of light energy (light waves are crucial)
Wavelength (sensation of color)
Distance between peaks of the light wave
Corresponds to our sensation of color
ROYGBIV
Short wavelengths = violets and blues
®
Long wavelength = reds and oranges
®
§
Amplitude (volume)
Intensity of the light wave
Corresponds to our sensation of brightness
Small amplitude - dull color
®
Great amplitude - bright color
®
§
Structure and function
Rods - cells in the periphery of the retina sensitive to light
§
Cones - cells in the center of the retina (Fovea) sensitive to focus and
color perception
§
2 theories of color vision
Trichromatic (Tri) theory (Young-Hemholtz)
Any color can be created by combining red, green, and blue light in
varying combinations
3 cones in the eyes
Cone 1 - sensitive to blue
®
Cone 2 - sensitive to green
®
Cone 3 - sensitive to red
®
Experience of colors results from mixing different levels of
response from these 3 cones
Ex. Color blindness - results from one set of cones not working well
More common in males
®
2 types
Red - green
Blue -yellow
®
§
Opponent Process theory
Opposing retinal processes enable color vision
Neural impulses are antagonistic (a stimulus that elicits a response
from the "red" and depresses a response of the "green")
ON - red, blue, white / OFF - green, yellow, black
Red - green
®
Blue -yellow
®
Black - white
®
§
Audition
Q: How do we turn variations in air pressure (physical stimulus - sound waves)
into our sense of hearing (psychological experience)
2 aspects of sound waves
Frequency (pitch)
The # of complete cycles per unit time (Hertz - cycles per second)
Corresponds to our psychological sensation of pitch
§
Amplitude (volume)
The intensity of the wave
Corresponds to our physical sensation of volume
§
Hearing - perceiving pitch, volume, and location
Perceiving pitch -high vs. low sounds
Place theory - different pitches produce responses on different
places on the basilar membrane
Works well with high-pitched sounds
®
Sound frequencies stimulate the basilar membrane at
specific places which results in perceived pitch
®
Frequency theory - different pitches cause the basilar membrane,
itself, to vibrate at different frequencies
Works well with low-pitched sounds
®
Speed of nerve impulse traveling up the auditory nerve
matches the frequency of a tone and enables us to know the
pitch
®
§
Perceiving volume - loud vs. soft sounds
Not movement of basilar membrane BUT # of stimulated hair cells
§
Perceiving location - where is that sound coming from
Why do we have 2 ears?
Left vs. right (ear on each side helps us know direction of
sound), up vs. down (one ear is lightly higher than the
other), front vs. behind (ears are equidistant from front and
back of head, cannot distinguish between front and back if
sound is directed aimed at back or front, we turn our heads
to determine front vs. behind)
®
What's up with your own voice?
Air coming out of your mouth (external sound) + bone
conduction (internal sound)
®
§
Perception
Organization and interpretation
There is NOT a 1:1 correspondence between our perceptual
representation of the world and the physical reality of the world
WHY?
Physical information is ambiguous
Ex. Seeing your roommate across the pond - looks
small
They are far away, not 3 inches tall - things look
smaller further away
}
Ex. "What's wrong, honey?" "Nothing!"
Learn how to interpret ambiguity
}
®
We take available info and interpret it based on what we know
about our world
§
Perceptual illusions
Illusion - case where the rules that we use to interpret the world (which
are usually true) are NOT TRUE and lead us to mis-interpretation
When the rules we apply to visual stimulus DOES NOT work
§
Examples of illusions
Vertical vs. horizontal lines
Context effects
Provides us with ways to interpret 2 things differently
®
Experience effects
Muller Lyer
®
Ponzo
®
§
Why so many visual illusions?
Visual capture - vision dominates
Ex. Stare at phone when listening to voicemail
®
§
Gestalt psychology - perceptual rules
§Tried to specify the "rules of perception" for how we distinguish
coherent, separate objects
German word for "form" or "whole"
§We work hard to perceive coherence in our environment
The world composed of discrete, separate objects
Perceive certain elemental forms and combine them together to
create complex whole scenes
§Rules
1. Figure-ground
a) Perceive object as distinct from its surroundings
i) Ex. The plane (figure) is separate from the sky
2. Grouping rules
a) Proximity -group nearby objects together
b) Similarity - group figures that are similar
c) Continuity -perceive continuous patterns
d) Connectedness - spots, lines, and areas are seen as united
when connected
i) We opt for most simplistic interpretation - simplicity
e) Closure - fill in gaps
i) Illusion of contours
ii) Sometimes local features assist with the perception of
global features BUT sometimes global features assist
with local features
3. Perceptual constancy
a) Able to perceive an object as unchanging even though the
stimuli we receive from it change
b) Once we lock onto a particular interpretation of stimulus,
we tend to stick with that perception
i) Size constancy
ii) Shape constancy
iii) When constancy rules fail us (exceptions)
One. Neckar cube
Two. Patterns with multiple interpretations
4. Perceptual set
a) Expectations are a big determinant of how we perceive a
scene
b) To BELIEVE is to SEE
c) examples
i) Stereotypes - babies (boy vs. girl - baby boy waves his
arms around = fighter, baby girls waves = dancer)
ii) Coast example - coast, coast, coast, coast, what do you
put into a toaster?
Depth perception
§How do we perceive depth? (how to turn 2D into 3D)
2 main sources of info
®Binocular cues
Rely on fact that we have 2 eyes (2 eyes work together
to form one visual field)
Each eye produces slightly different image because
the eyes are in different locations
Our brain imposes structure on the environment
(Gestalt rules)
Averages the 2 images from our 2 eyes
Brain informs/provides structure for perception
Examples
}Retinal disparity
Each of our eyes sees the world from a
slightly different angle
Images from the 2 eyes differ
The larger the difference (disparity)
between 2 images the retinas receive, the
closer the object is to our eyes
}Convergence
The closer something is, the larger the
angle formed by the 2 eyes
2 eyes move inward for near objects,
move outward for farther objects
®Monocular cues
Can be perceived with 1 eye only
Brain makes use of information that exists in the
environment
Examples
}Interposition
If A blocks B, then A must be closer
}Relative size
If 2 items are similar in appearance, then
the one that looks smaller is farther away
}Clarity
Clearer is closer
}Texture gradient
Coarse is close, smoother is farther away
}Relative height
Things higher in our field of vision are
perceived as further away
}Relative motion - motion parallax
Things further away move more slowly
(ex. Look out the window on a train)
}Linear perspective
Parallel lines converge in the distance
}Relative brightness - light and shadow
Closer things are brighter
If A casts a shadow on B, then A is in front
of B
Perceptual adaptation
§Humans are quite consistent
Fall prey to the same illusion errors
§Humans are highly adaptive to changing environments
If some fundamental change in the environment occurs, we can
adapt quickly
Extra sensory perception (ESP)
§Skills
Telepathy - reading another's mind
Clairvoyance - perceiving remote events (look into past)
Pre-recognition - perceiving future events
§Are ESP phenomenon reliable?
Published psychics - 1 in 243 are correct
Police investigations - 1 in 100 are correct
People's dreams - no better than chance, impossible to verify
Why do we believe?
Vivid experiences are powerful
Unaware of origin of our thoughts
Chance occurrences
Illusion of personal control
It's sort of fun
§
§NONE of this proves that ESP does NOT exist
Sensation and Perception
Tuesday, October 2, 2018
11:21 AM
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 8 pages and 3 million more documents.

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Sensation vs. PerceptionI.
PsychophysicsII.
VisionIII.
AuditionIV.
Experiencing events - 2 stages
Stage 1 - Sensation
Converting the physical world into a mental representation
(transduction)
Ex. Variations of light ---> experience of color
Ex. Variations of air pressure ---> experience of sound
§
Relaying that information to the brain (conduction)
§
Stage 2 - Perception
Select, organize and interpret these mental representations
Ex. We can recognize the color green
Ex. We can distinguish Bach from Bruno Mars
§
Psychophysics
The study of the relationship between physical characteristics of stimuli
(energy) and our psychological experience of them
Ex. Light ---> brightness, sound ---> volume, pressure ---> weight,
taste ---> sweetness/bitterness
§
Absolute thresholds: smallest magnitude of a stimulus that can be reliably
discriminated from NO stimulus at least 50% of the time
Difference threshold: minimum difference between 2 stimuli that a person
can detect at least 50% of the time (JUST noticeable difference)
Signal detection theory: predicts how and when we will detect the presence
of a stimulus amidst background stimulation
Complex decision mechanisms are involved to determine if a stimulus
exists
§
Based on…
Stimulus strength
Our experiences - expectations, motivation, level of fatigue
Ex. Sounds in my house vs. sounds outside (expected a
murdered vs. it's just background noise)
®
§
Absolute thresholds and difference thresholds are NOT fixed
Our sensitivity to a stimulus varies based on experiences
Factors affecting Absolute and Difference thresholds
Chance variation - noise in the system influences sensitivity
Stimulus intensity
Weber's law - the greater the intensity of a stimulus, the larger
the difference must be to detect a difference
Must differ by a constant proportion
®
Sensory adaptation - our sensitivity to an unchanging stimulus
diminishes
Ex. First getting into a hot tub vs. getting used to the heat, want it
to be hotter when the temp. hasn't changed
Vision
Q: how do we turn light energy (light waves - physical stimulus) into vision
(psychological experience)
2 aspects of light energy (light waves are crucial)
Wavelength (sensation of color)
Distance between peaks of the light wave
Corresponds to our sensation of color
ROYGBIV
Short wavelengths = violets and blues
®
Long wavelength = reds and oranges
®
Amplitude (volume)
Intensity of the light wave
Corresponds to our sensation of brightness
Small amplitude - dull color
®
Great amplitude - bright color
®
Structure and function
Rods - cells in the periphery of the retina sensitive to light
Cones - cells in the center of the retina (Fovea) sensitive to focus and
color perception
2 theories of color vision
Trichromatic (Tri) theory (Young-Hemholtz)
Any color can be created by combining red, green, and blue light in
varying combinations
3 cones in the eyes
Cone 1 - sensitive to blue
®
Cone 2 - sensitive to green
®
Cone 3 - sensitive to red
®
Experience of colors results from mixing different levels of
response from these 3 cones
Ex. Color blindness - results from one set of cones not working well
More common in males
®
2 types
Red - green
Blue -yellow
®
Opponent Process theory
Opposing retinal processes enable color vision
Neural impulses are antagonistic (a stimulus that elicits a response
from the "red" and depresses a response of the "green")
ON - red, blue, white / OFF - green, yellow, black
Red - green
®
Blue -yellow
®
Black - white
®
§
Audition
Q: How do we turn variations in air pressure (physical stimulus - sound waves)
into our sense of hearing (psychological experience)
2 aspects of sound waves
Frequency (pitch)
The # of complete cycles per unit time (Hertz - cycles per second)
Corresponds to our psychological sensation of pitch
§
Amplitude (volume)
The intensity of the wave
Corresponds to our physical sensation of volume
§
Hearing - perceiving pitch, volume, and location
Perceiving pitch -high vs. low sounds
Place theory - different pitches produce responses on different
places on the basilar membrane
Works well with high-pitched sounds
®
Sound frequencies stimulate the basilar membrane at
specific places which results in perceived pitch
®
Frequency theory - different pitches cause the basilar membrane,
itself, to vibrate at different frequencies
Works well with low-pitched sounds
®
Speed of nerve impulse traveling up the auditory nerve
matches the frequency of a tone and enables us to know the
pitch
®
§
Perceiving volume - loud vs. soft sounds
Not movement of basilar membrane BUT # of stimulated hair cells
§
Perceiving location - where is that sound coming from
Why do we have 2 ears?
Left vs. right (ear on each side helps us know direction of
sound), up vs. down (one ear is lightly higher than the
other), front vs. behind (ears are equidistant from front and
back of head, cannot distinguish between front and back if
sound is directed aimed at back or front, we turn our heads
to determine front vs. behind)
®
What's up with your own voice?
Air coming out of your mouth (external sound) + bone
conduction (internal sound)
®
§
Perception
Organization and interpretation
There is NOT a 1:1 correspondence between our perceptual
representation of the world and the physical reality of the world
WHY?
Physical information is ambiguous
Ex. Seeing your roommate across the pond - looks
small
They are far away, not 3 inches tall - things look
smaller further away
}
Ex. "What's wrong, honey?" "Nothing!"
Learn how to interpret ambiguity
}
®
We take available info and interpret it based on what we know
about our world
§
Perceptual illusions
Illusion - case where the rules that we use to interpret the world (which
are usually true) are NOT TRUE and lead us to mis-interpretation
When the rules we apply to visual stimulus DOES NOT work
§
Examples of illusions
Vertical vs. horizontal lines
Context effects
Provides us with ways to interpret 2 things differently
®
Experience effects
Muller Lyer
®
Ponzo
®
§
Why so many visual illusions?
Visual capture - vision dominates
Ex. Stare at phone when listening to voicemail
®
§
Gestalt psychology - perceptual rules
§Tried to specify the "rules of perception" for how we distinguish
coherent, separate objects
German word for "form" or "whole"
§We work hard to perceive coherence in our environment
The world composed of discrete, separate objects
Perceive certain elemental forms and combine them together to
create complex whole scenes
§Rules
1. Figure-ground
a) Perceive object as distinct from its surroundings
i) Ex. The plane (figure) is separate from the sky
2. Grouping rules
a) Proximity -group nearby objects together
b) Similarity - group figures that are similar
c) Continuity -perceive continuous patterns
d) Connectedness - spots, lines, and areas are seen as united
when connected
i) We opt for most simplistic interpretation - simplicity
e) Closure - fill in gaps
i) Illusion of contours
ii) Sometimes local features assist with the perception of
global features BUT sometimes global features assist
with local features
3. Perceptual constancy
a) Able to perceive an object as unchanging even though the
stimuli we receive from it change
b) Once we lock onto a particular interpretation of stimulus,
we tend to stick with that perception
i) Size constancy
ii) Shape constancy
iii) When constancy rules fail us (exceptions)
One. Neckar cube
Two. Patterns with multiple interpretations
4. Perceptual set
a) Expectations are a big determinant of how we perceive a
scene
b) To BELIEVE is to SEE
c) examples
i) Stereotypes - babies (boy vs. girl - baby boy waves his
arms around = fighter, baby girls waves = dancer)
ii) Coast example - coast, coast, coast, coast, what do you
put into a toaster?
Depth perception
§How do we perceive depth? (how to turn 2D into 3D)
2 main sources of info
®Binocular cues
Rely on fact that we have 2 eyes (2 eyes work together
to form one visual field)
Each eye produces slightly different image because
the eyes are in different locations
Our brain imposes structure on the environment
(Gestalt rules)
Averages the 2 images from our 2 eyes
Brain informs/provides structure for perception
Examples
}Retinal disparity
Each of our eyes sees the world from a
slightly different angle
Images from the 2 eyes differ
The larger the difference (disparity)
between 2 images the retinas receive, the
closer the object is to our eyes
}Convergence
The closer something is, the larger the
angle formed by the 2 eyes
2 eyes move inward for near objects,
move outward for farther objects
®Monocular cues
Can be perceived with 1 eye only
Brain makes use of information that exists in the
environment
Examples
}Interposition
If A blocks B, then A must be closer
}Relative size
If 2 items are similar in appearance, then
the one that looks smaller is farther away
}Clarity
Clearer is closer
}Texture gradient
Coarse is close, smoother is farther away
}Relative height
Things higher in our field of vision are
perceived as further away
}Relative motion - motion parallax
Things further away move more slowly
(ex. Look out the window on a train)
}Linear perspective
Parallel lines converge in the distance
}Relative brightness - light and shadow
Closer things are brighter
If A casts a shadow on B, then A is in front
of B
Perceptual adaptation
§Humans are quite consistent
Fall prey to the same illusion errors
§Humans are highly adaptive to changing environments
If some fundamental change in the environment occurs, we can
adapt quickly
Extra sensory perception (ESP)
§Skills
Telepathy - reading another's mind
Clairvoyance - perceiving remote events (look into past)
Pre-recognition - perceiving future events
§Are ESP phenomenon reliable?
Published psychics - 1 in 243 are correct
Police investigations - 1 in 100 are correct
People's dreams - no better than chance, impossible to verify
Why do we believe?
Vivid experiences are powerful
Unaware of origin of our thoughts
Chance occurrences
Illusion of personal control
It's sort of fun
§
§NONE of this proves that ESP does NOT exist
Sensation and Perception
Tuesday, October 2, 2018 11:21 AM
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 8 pages and 3 million more documents.

Already have an account? Log in
Sensation vs. PerceptionI.
PsychophysicsII.
VisionIII.
AuditionIV.
Experiencing events - 2 stages
Stage 1 - Sensation
Converting the physical world into a mental representation
(transduction)
Ex. Variations of light ---> experience of color
Ex. Variations of air pressure ---> experience of sound
§
Relaying that information to the brain (conduction)
§
Stage 2 - Perception
Select, organize and interpret these mental representations
Ex. We can recognize the color green
Ex. We can distinguish Bach from Bruno Mars
§
Psychophysics
The study of the relationship between physical characteristics of stimuli
(energy) and our psychological experience of them
Ex. Light ---> brightness, sound ---> volume, pressure ---> weight,
taste ---> sweetness/bitterness
§
Absolute thresholds: smallest magnitude of a stimulus that can be reliably
discriminated from NO stimulus at least 50% of the time
Difference threshold: minimum difference between 2 stimuli that a person
can detect at least 50% of the time (JUST noticeable difference)
Signal detection theory: predicts how and when we will detect the presence
of a stimulus amidst background stimulation
Complex decision mechanisms are involved to determine if a stimulus
exists
§
Based on…
Stimulus strength
Our experiences - expectations, motivation, level of fatigue
Ex. Sounds in my house vs. sounds outside (expected a
murdered vs. it's just background noise)
®
§
Absolute thresholds and difference thresholds are NOT fixed
Our sensitivity to a stimulus varies based on experiences
§
Factors affecting Absolute and Difference thresholds
Chance variation - noise in the system influences sensitivity
§
Stimulus intensity
Weber's law - the greater the intensity of a stimulus, the larger
the difference must be to detect a difference
Must differ by a constant proportion
®
§
Sensory adaptation - our sensitivity to an unchanging stimulus
diminishes
Ex. First getting into a hot tub vs. getting used to the heat, want it
to be hotter when the temp. hasn't changed
§
Vision
Q: how do we turn light energy (light waves - physical stimulus) into vision
(psychological experience)
2 aspects of light energy (light waves are crucial)
Wavelength (sensation of color)
Distance between peaks of the light wave
Corresponds to our sensation of color
ROYGBIV
Short wavelengths = violets and blues
®
Long wavelength = reds and oranges
®
§
Amplitude (volume)
Intensity of the light wave
Corresponds to our sensation of brightness
Small amplitude - dull color
®
Great amplitude - bright color
®
§
Structure and function
Rods - cells in the periphery of the retina sensitive to light
§
Cones - cells in the center of the retina (Fovea) sensitive to focus and
color perception
§
2 theories of color vision
Trichromatic (Tri) theory (Young-Hemholtz)
Any color can be created by combining red, green, and blue light in
varying combinations
3 cones in the eyes
Cone 1 - sensitive to blue
®
Cone 2 - sensitive to green
®
Cone 3 - sensitive to red
®
Experience of colors results from mixing different levels of
response from these 3 cones
Ex. Color blindness - results from one set of cones not working well
More common in males
®
2 types
Red - green
Blue -yellow
®
§
Opponent Process theory
Opposing retinal processes enable color vision
Neural impulses are antagonistic (a stimulus that elicits a response
from the "red" and depresses a response of the "green")
ON - red, blue, white / OFF - green, yellow, black
Red - green
®
Blue -yellow
®
Black - white
®
Audition
Q: How do we turn variations in air pressure (physical stimulus - sound waves)
into our sense of hearing (psychological experience)
2 aspects of sound waves
Frequency (pitch)
The # of complete cycles per unit time (Hertz - cycles per second)
Corresponds to our psychological sensation of pitch
Amplitude (volume)
The intensity of the wave
Corresponds to our physical sensation of volume
Hearing - perceiving pitch, volume, and location
Perceiving pitch -high vs. low sounds
Place theory - different pitches produce responses on different
places on the basilar membrane
Works well with high-pitched sounds
®
Sound frequencies stimulate the basilar membrane at
specific places which results in perceived pitch
®
Frequency theory - different pitches cause the basilar membrane,
itself, to vibrate at different frequencies
Works well with low-pitched sounds
®
Speed of nerve impulse traveling up the auditory nerve
matches the frequency of a tone and enables us to know the
pitch
®
Perceiving volume - loud vs. soft sounds
Not movement of basilar membrane BUT # of stimulated hair cells
§
Perceiving location - where is that sound coming from
Why do we have 2 ears?
Left vs. right (ear on each side helps us know direction of
sound), up vs. down (one ear is lightly higher than the
other), front vs. behind (ears are equidistant from front and
back of head, cannot distinguish between front and back if
sound is directed aimed at back or front, we turn our heads
to determine front vs. behind)
®
What's up with your own voice?
Air coming out of your mouth (external sound) + bone
conduction (internal sound)
®
§
Perception
Organization and interpretation
There is NOT a 1:1 correspondence between our perceptual
representation of the world and the physical reality of the world
WHY?
Physical information is ambiguous
Ex. Seeing your roommate across the pond - looks
small
They are far away, not 3 inches tall - things look
smaller further away
}
Ex. "What's wrong, honey?" "Nothing!"
Learn how to interpret ambiguity
}
®
We take available info and interpret it based on what we know
about our world
§
Perceptual illusions
Illusion - case where the rules that we use to interpret the world (which
are usually true) are NOT TRUE and lead us to mis-interpretation
When the rules we apply to visual stimulus DOES NOT work
§
Examples of illusions
Vertical vs. horizontal lines
Context effects
Provides us with ways to interpret 2 things differently
®
Experience effects
Muller Lyer
®
Ponzo
®
§
Why so many visual illusions?
Visual capture - vision dominates
Ex. Stare at phone when listening to voicemail
®
§
Gestalt psychology - perceptual rules
§Tried to specify the "rules of perception" for how we distinguish
coherent, separate objects
German word for "form" or "whole"
§We work hard to perceive coherence in our environment
The world composed of discrete, separate objects
Perceive certain elemental forms and combine them together to
create complex whole scenes
§Rules
1. Figure-ground
a) Perceive object as distinct from its surroundings
i) Ex. The plane (figure) is separate from the sky
2. Grouping rules
a) Proximity -group nearby objects together
b) Similarity - group figures that are similar
c) Continuity -perceive continuous patterns
d) Connectedness - spots, lines, and areas are seen as united
when connected
i) We opt for most simplistic interpretation - simplicity
e) Closure - fill in gaps
i) Illusion of contours
ii) Sometimes local features assist with the perception of
global features BUT sometimes global features assist
with local features
3. Perceptual constancy
a) Able to perceive an object as unchanging even though the
stimuli we receive from it change
b) Once we lock onto a particular interpretation of stimulus,
we tend to stick with that perception
i) Size constancy
ii) Shape constancy
iii) When constancy rules fail us (exceptions)
One. Neckar cube
Two. Patterns with multiple interpretations
4. Perceptual set
a) Expectations are a big determinant of how we perceive a
scene
b) To BELIEVE is to SEE
c) examples
i) Stereotypes - babies (boy vs. girl - baby boy waves his
arms around = fighter, baby girls waves = dancer)
ii) Coast example - coast, coast, coast, coast, what do you
put into a toaster?
Depth perception
§How do we perceive depth? (how to turn 2D into 3D)
2 main sources of info
®Binocular cues
Rely on fact that we have 2 eyes (2 eyes work together
to form one visual field)
Each eye produces slightly different image because
the eyes are in different locations
Our brain imposes structure on the environment
(Gestalt rules)
Averages the 2 images from our 2 eyes
Brain informs/provides structure for perception
Examples
}Retinal disparity
Each of our eyes sees the world from a
slightly different angle
Images from the 2 eyes differ
The larger the difference (disparity)
between 2 images the retinas receive, the
closer the object is to our eyes
}Convergence
The closer something is, the larger the
angle formed by the 2 eyes
2 eyes move inward for near objects,
move outward for farther objects
®Monocular cues
Can be perceived with 1 eye only
Brain makes use of information that exists in the
environment
Examples
}Interposition
If A blocks B, then A must be closer
}Relative size
If 2 items are similar in appearance, then
the one that looks smaller is farther away
}Clarity
Clearer is closer
}Texture gradient
Coarse is close, smoother is farther away
}Relative height
Things higher in our field of vision are
perceived as further away
}Relative motion - motion parallax
Things further away move more slowly
(ex. Look out the window on a train)
}Linear perspective
Parallel lines converge in the distance
}Relative brightness - light and shadow
Closer things are brighter
If A casts a shadow on B, then A is in front
of B
Perceptual adaptation
§Humans are quite consistent
Fall prey to the same illusion errors
§Humans are highly adaptive to changing environments
If some fundamental change in the environment occurs, we can
adapt quickly
Extra sensory perception (ESP)
§Skills
Telepathy - reading another's mind
Clairvoyance - perceiving remote events (look into past)
Pre-recognition - perceiving future events
§Are ESP phenomenon reliable?
Published psychics - 1 in 243 are correct
Police investigations - 1 in 100 are correct
People's dreams - no better than chance, impossible to verify
Why do we believe?
Vivid experiences are powerful
Unaware of origin of our thoughts
Chance occurrences
Illusion of personal control
It's sort of fun
§
§NONE of this proves that ESP does NOT exist
Sensation and Perception
Tuesday, October 2, 2018 11:21 AM
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Document Summary

Converting the physical world into a mental representation (transduction) Variations of air pressure ---> experience of sound. The study of the relationship between physical characteristics of stimuli (energy) and our psychological experience of them. Light ---> brightness, sound ---> volume, pressure ---> weight, taste ---> sweetness/bitterness. Absolute thresholds: smallest magnitude of a stimulus that can be reliably discriminated from no stimulus at least 50% of the time. Difference threshold: minimum difference between 2 stimuli that a person can detect at least 50% of the time (just noticeable difference) Signal detection theory: predicts how and when we will detect the presence of a stimulus amidst background stimulation. Complex decision mechanisms are involved to determine if a stimulus exists. Our experiences - expectations, motivation, level of fatigue. Sounds in my house vs. sounds outside (expected a murdered vs. it"s just background noise) Absolute thresholds and difference thresholds are not fixed. Our sensitivity to a stimulus varies based on experiences.

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