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SENSATION & PERCEPTION
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Do Now:
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Could you live without any one of your senses?
BASIC PRINCIPLES
Sensation: sensory receptors & nervous system
receive and represent information from the
environment
 Perception: process of organizing and
interpreting sensory info
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Recognize meaningful objects and events
PROCESSING
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Bottom-Up Processing
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Sensory receptors to
brain’s integration of
sensory info
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Top-Down Processing
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Constructs perceptions
from the sensory from
sensory input by
drawing on experience
and expectations
TRANSDUCTION
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Sensory System
Receives stimuli
 Transforms it into neural stimulation
 Delivers info to brain
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This process of changing one form of energy into something
your brain can use is transduction
What are some of the strengths and weaknesses of
this system?
THRESHOLD
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Right now we are being hit with tons of different waves (xrays, radio waves, uv and infrared light, sound waves). Why
don’t we notice these?
Absolute Threshold
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The least amount of stimulation needed to detect a stimulus
50% of the time
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i.e. Hearing tests
Signal Detection Theory
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Predicts when we will detect weak signals (hits/false alarms)
Tests sensations but also our expectations
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Subliminal: stimuli you detect less than 50% of the time
Prime: activation of an association and thereby predisposing
you to form a memory or response
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Often unconscious of this
Image test
BREAK TIME!
You’re driving a bus with 12 passengers.
 At your first stop, 6 passengers get off.
 At the second stop, 3 get off.
 At the third stop, 2 more get off but 3 new people
get on.
 What color are the bus driver’s eyes?
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Can we be controlled by subliminal messages?
DIFFERENCE THRESHOLDS
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To function we need:
Low enough absolute thresholds so we can see, hear,
taste, feel, and smell important stimuli
 Need to know the small differences among stimuli
 Difference Threshold:
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The just noticeable difference
 Minimum dif. a person can detect between any two stimuli
half the time
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Weber’s Law:
 For the average person to perceive a difference, 2 stimuli
must differ by a constant proportion.
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Ex. Two lights must differ in intensity by 8%
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Sensory Adaptation
Decrease in sensitivity as a result of constant
stimulation
 We perceive the world not exactly as it is, but as it is
useful for us to perceive it.
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What are some examples?
 How do TV editors do this? YouTube videos use this to their
advantage?
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Perceptual Set
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A set of mental tendencies and assumptions that
impact what we perceive (top-down)
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What determines this? Schemas
 Schemas are experiences that form concepts that help us
organize and interpret unfamiliar information
 How do we know what pronoun to use for a newborn?
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Context Effects
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A stimulus might trigger different perceptions
because of our different mental sets but…
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…also because of the context
 Eel is on the wagon or eel is on the orange
Emotion & Motivation
Sad music
 Water bottle seems closer when thirsty
 If you’re tired when walking the destination seems further
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VISION
LIGHT ENERGY
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Only see a small portion
of all rays
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Other organisms see
different spectrums
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Wavelength
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Hue
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Distance from one peak
to next
Color we experience
Determined by
wavelength
Intensity
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Amount of energy
Amplitude
Brightness
THE EYE
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Pupil
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Iris
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Small adjustable opening
Light passes through
Controls pupil
Colored muscle
Light/ Emotions
Lens
Focuses on incoming light into
an image
 Accommodation: adjusts
curvature
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Retina
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Multilayered image on eye’s
inner surface
THE RETINA (CON’T)
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Receives info as upside down
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Sends neural impulses – brain perceives this images as
right side up
2 types of cells
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Rods
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Retinal cells detect black, white, gray
Use at night and for peripheral vision
Share bipolar cells
Cones
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Retinal cells near center
Color, fine detail, daylight (fovea- point of central focus on
retina)
Each has one bipolar cell
Bipolar cells send to ganglion cells: form optic nerve
 Carry info to brain (thalamus to distribute)
 Where optic nerve leaves eye there are no cells: blind spot
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Brain fills in the hole
VISUAL INFORMATION PROCESSING
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Retina begins processing info
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Frog’s eye: see “fly like” movement
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fight/flight response
Feature Detection
Respond to specific features
 Cortical areas respond to details
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What if this area was damaged?
 Brain’s face processing is different than object perception
 Cells are specialized: movement, gaze, posture, etc.
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Parallel Processing
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Doing many things at once
Divide a scene
 Facial recognition
 Blind sight: say they see nothing but guess correctly
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COLOR VISION
2.
Item rejects color we perceive them
Color is mental construction
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Young Helmholtz Thrichromatic Theory
1.
3 types of color receptors (red-green-blue)
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Sensitive to one color
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Ex. Yellow stimulates red and green receptors
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Deficiency: lack receptors
Opponent Processing Theory
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Red-green, yellow-blue, white-black
Allows color vision to happen
Receptor turns on with red and off with green
VISUAL ORGANIZATION
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Gestalt: organization of sensations in a “whole”
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Filter info and make meaning
Form Perception
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Figure and ground
Grouping
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Order and form to stimuli
Proximity (close), Continuity (smooth), Closure (fill in gaps)
Depth Perception
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Estimate object’s distance
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Binocular cues
 Two eyes to judge distance
 Retinal Disparity: difference between two images; closer
object is determined
Monocular cues
 Depth cues available to each eye
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Motion perception
Phi Phenomenon: Lights can recreate this
PERCEPTUAL CONSTANCY
Top-down
 Perceive objects as unchanging, even if illumination
and retinal image change
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Color and Brightness Constancy
 Shape and Size Constancy
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VISUAL INTERPRETATION
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Perceptual adaptation
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Will adapt given new visual input
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e.g. glasses
HEARING (AUDITION)
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Sound waves:
amplitude = loudness
 frequency = pitch
 measure in decibels
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The Ear
Outer ear – eardrum (vibrates)
 Middle ear – hammer, anvil, stirrup
 Inner ear – cochlea (oval window): vibrates and fills
with fludid
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Bends hair cells(auditory nerve) sends to auditory cortex
HEARING DAMAGE
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Sorineural Hearing Loss
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nerve deafness
Conduction Hearing Loss
rare
 damage to mechanical system
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Treatment
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Cochlear implant
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Restores hearing with nerve damage
TOUCH
Crucial to development (needed as an infant)
 Paiin
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Nocireceptors: dects harmful temp, pressure, chemicals
 Gate-Control Theory
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Spinal cord either blocks or allows pain to pass to the brain
 What holistic approaches help to inhibit pain?
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Physical Phenomena
Endorphins
 Phantom limb sensations
 Psych influences
 Social-cultural influences
 Controlling pain
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TASTE
Sweet
 Salty
 Sour
 Bitter
 Umami
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Sensory interaction
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One sense influences another
SMELL
Women have better sense of smell
 What types of factors might contribute to having
a worse sense of smell?
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Associate smell with memories
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Learned Associations
BODY POSITION & MOVEMENT