Myers Ch 6
Sensation and Perception
o Differences
Sensation is sensory receptors
What is transmitted to the brain
Bottom-up
o Starts at the sensory receptors and works up to higher
levels of processing
Perception
How input is organized and interpreted
Top-down
o Constructs perceptions from the sensory input by drawing
on experiences/expectations
Perceptual set
o Assumptions that affect what we sense
o Predisposition to react a certain way
o Expectation
What we think we are going to sense
Sometimes having background information makes
us perceive something a certain way
Like Loch Ness monster photo, when if you didn’t
know the story, you’d most likely see a tree limb
o Context
Related to culture
Our experiences shape our perception
Ex: someone holding a gun is more likely to assume
someone else also has a gun, even if its just a
phone/wallet
o Motivation/emotion
Being a certain emotion influences perception
Can make us more or less likely to do something
Ex: angry people are more likely to see actions as
violent or objects as weapons
Ex: a hill looks steeper to someone either sad or
carrying something heavy
o Illusions
Help us understand normal perceptual processes
Illustrate principles of human perception
Ex: looking at a photo of a woman who is angry on
the left and scared on the right and neutral in the
middle, your perception of the middle photo
changes based on which emotion you saw first
, Ex: a photo of a woman at three angles, you will
see her as either older or younger depending on
which angle you see first
Sensory Adaptation
o Diminished sensitivity due to constant stimulation
o Ex: nose blind
o We only sense a limited range of stimuli in the world
o Our mind interprets stimuli to create a model of the world
Useful, maybe not accurate
o Transduction
Conversion of one form of energy into another
Transforming senses into neural impulses
o Thresholds
Absolute threshold
Minimum stimulus energy to detect a stimulus 50% of the time
Difference threshold
Minimum difference detected between two stimuli 50% of the
time
Increases with the size of stimulus
o Ex: easier to detect a small change within a small stimulus,
like music being quiet is easier to tell when the volume is
turned up slightly than loud music being turned up slightly
Just noticeable difference (jnd)
o Ex: differences in people’s voices
Weber’s Law
o To be perceived as different, two stimuli must differ by a
constant minimum %
Subliminal perception
Below one’s absolute threshold for conscious awareness
Weak stimulus that still affects you but youre unaware of
Vision
o Visual Processing Stream
Light as stimulus input
Electromagnetic energy perceived as colors
Wavelength: distance from one wave peak to the next
o Determines hue: the color we see
o Intensity: the amount of energy in light waves
Influences brightness
Optic nerve projects to thalamus
Thalamus projects to primary visual cortex in occipital lobe
Retinotopic organization
o In the cortex
o Mapping of visual input from retina to neurons
Sensation and Perception
o Differences
Sensation is sensory receptors
What is transmitted to the brain
Bottom-up
o Starts at the sensory receptors and works up to higher
levels of processing
Perception
How input is organized and interpreted
Top-down
o Constructs perceptions from the sensory input by drawing
on experiences/expectations
Perceptual set
o Assumptions that affect what we sense
o Predisposition to react a certain way
o Expectation
What we think we are going to sense
Sometimes having background information makes
us perceive something a certain way
Like Loch Ness monster photo, when if you didn’t
know the story, you’d most likely see a tree limb
o Context
Related to culture
Our experiences shape our perception
Ex: someone holding a gun is more likely to assume
someone else also has a gun, even if its just a
phone/wallet
o Motivation/emotion
Being a certain emotion influences perception
Can make us more or less likely to do something
Ex: angry people are more likely to see actions as
violent or objects as weapons
Ex: a hill looks steeper to someone either sad or
carrying something heavy
o Illusions
Help us understand normal perceptual processes
Illustrate principles of human perception
Ex: looking at a photo of a woman who is angry on
the left and scared on the right and neutral in the
middle, your perception of the middle photo
changes based on which emotion you saw first
, Ex: a photo of a woman at three angles, you will
see her as either older or younger depending on
which angle you see first
Sensory Adaptation
o Diminished sensitivity due to constant stimulation
o Ex: nose blind
o We only sense a limited range of stimuli in the world
o Our mind interprets stimuli to create a model of the world
Useful, maybe not accurate
o Transduction
Conversion of one form of energy into another
Transforming senses into neural impulses
o Thresholds
Absolute threshold
Minimum stimulus energy to detect a stimulus 50% of the time
Difference threshold
Minimum difference detected between two stimuli 50% of the
time
Increases with the size of stimulus
o Ex: easier to detect a small change within a small stimulus,
like music being quiet is easier to tell when the volume is
turned up slightly than loud music being turned up slightly
Just noticeable difference (jnd)
o Ex: differences in people’s voices
Weber’s Law
o To be perceived as different, two stimuli must differ by a
constant minimum %
Subliminal perception
Below one’s absolute threshold for conscious awareness
Weak stimulus that still affects you but youre unaware of
Vision
o Visual Processing Stream
Light as stimulus input
Electromagnetic energy perceived as colors
Wavelength: distance from one wave peak to the next
o Determines hue: the color we see
o Intensity: the amount of energy in light waves
Influences brightness
Optic nerve projects to thalamus
Thalamus projects to primary visual cortex in occipital lobe
Retinotopic organization
o In the cortex
o Mapping of visual input from retina to neurons
