Introductory Psychology:
Sensation
AP PSYCHOLOGY: UNIT V
Sensation
 Vision, hearing, smell, taste, touch, pain &
body position

Similarities?
Transduce stimulus energy into neural impulses
 More sensitive to change than to constant stimulation
 Provide us with information regarding our environment


Differences?
Each requires a different form of stimulus energy
 Each sends information to a different region of the brain
for processing

Sensation:
Vision
PART ONE
Vision: The Stimulus Input
 The Stimulus Input
 Light energy (electromagnetic energy)

Two physical characteristics help to determine our
sensory experience of light
 Wavelength
• The distance from one peak to another
• Determines HUE (color)

Amplitude
• Height of each wave’s peak
• Determines INTENSITY (brightness)
Shorter wavelength – bluish colors
Longer wavelength – reddish colors
Great amplitude – bright colors
Small amplitude – dull colors
Vision: The Structure of the Eye
 Cornea
 Location/Structure


The clear bulge on the
front of the eyeball
Function
Protects the eye
 Bends light towards a
central focal point in
order to provide focus

Vision: The Structure of the Eye
 Pupil/Iris
 Location/Structure
Adjustable opening in the
center of the eye
 Surrounded by the iris (small
ring of muscle tissue; color)


Function

Controls the amount of light that is able to enter the eye
 In bright conditions the iris expands, making the pupil
smaller
 In dark conditions the iris contracts, making the pupil
larger
Vision: The Structure of the Eye
 Lens
 Location/Structure


A transparent structure
that is located behind the
pupil
Function

Focuses image on the back
of the eye (retina)
 Accommodation
• The process by which the eye’s lens changes shape to help
focus near or far objects on the retina
Vision: The Structure of the Eye
 Lens Problems
 Nearsightedness
Also known as myopia
 Eyeball may be too long
 Image focused in front of
the retina


Farsightedness
Also known as hyperopia
 Eyeball may be too short
 Image focused behind the
retina

Vision: The Structure of the Eye
 Retina
 Location/Structure


A multilayered, light-sensitive surface located at the back
of the eyeball
Function
Contains cells that convert light energy into nerve
impulses
 Includes three layers of cells
 Receptor cells (photoreceptors – cones & rods)
 Bipolar cells
 Ganglion cells

Vision: The Structure of the Eye
Cones
Rods
Number
6 million
120 million
Location
(in the retina)
Center
(fovea)
Edge
(periphery)
Color sensitive
Yes
No
Sensitivity in dim light?
Low
High
Ability to detect sharp
detail (acuity)?
High
Low
Photoreceptor Cells
Vision: The Structure of the Eye
 Bipolar Cells
 Receives message from the photoreceptors

Transmits message to the ganglion cells, which
are then considered “activated”
 Ganglion Cells
 The axons of the ganglion cells converge to form the
optic nerve
Light energy  Rods & Cones  Bipolar cells  Ganglion cells
Vision: The Structure of the Eye
 Optic Nerve
 Location/Structure


Nerve located at the back
of the eyeball
Function
Sends visual information
to the thalamus and then
to the occipital lobes
 Where the optic nerve leaves the eye, there are no rods or
cones, creating a blind spot

Vision: Visual Processing
 Feature Detectors
 Located in the visual cortex
 Nerve cells in the brain that respond to specific
features
Shape
 Angle
 Movement

Vision: Visual Processing
 Parallel Processing
 The processing of several aspects of a stimulus
simultaneously

The brain divides a visual scene into color, depth, form
and movement
Visual Information Processing
Feature Detection + Parallel Processing
•Color
•Motion
•Form
•Depth
All processed separately
but simultaneously
Vision: Color Vision
 Young-Helmholtz Trichromatic Theory
 (Hermann von Helmholtz & Thomas Young)
The theory that the retina contains three different color
receptors – red, green and blue
 When stimulated in combination, these receptors can
produce the perception of any color


Color Blindness?

Dichromatic Color Vision
 Individuals lack one of three receptors; usually the red
or green receptor
Vision: Color Vision
 Opponent-Process Theory of Color
 (Ewald Hering)


The theory that opposing retinal processes enable color
vision
 Red-Green
 Yellow-Blue
 Black-White
Light that stimulates one half of the pair inhibits the
other half

For example, some cells are stimulated by green and
inhibited by red, while others are stimulated by red and
inhibited by green
Sensation:
Hearing
PART TWO
Hearing: The Stimulus Input
 The Stimulus Input
 Sound energy

Two physical characteristics help to determine our
sensory experience of sound
 Wavelength/Frequency
• The distance from one peak to another
• Determines PITCH

Amplitude
• Height of each wave’s peak
• Determines LOUDNESS
Shorter wavelength – high-pitch
Longer wavelength – low-pitch
Great amplitude – loud sounds
Small amplitude – soft sounds
Hearing: The Structure of the Ear
 Outer Ear
 Relevant Structures


Pinna
Function

Channels sound waves
through the auditory canal to
the eardrum (tympanic
membrane)
Hearing: The Structure of the Ear
 Middle Ear
 Relevant Structures
(Eardrum)
 Hammer, Anvil, Stirrup


Function
Transmits the vibrations of
the eardrum through a
piston made of 3 tiny bones
 Hammer, anvil, stirrup
 These bones then transmit
the message to the cochlea

Hearing: The Structure of the Ear
 Inner Ear
 Relevant Structures
Cochlea
 Basilar Membrane


Function
The incoming vibrations cause movement in the
cochlea’s oval window, which then creates motion in the
cochlea’s fluid
 This motion causes movement in the basilar membrane
and its hair cells
 Eventually, the hair cells trigger an impulse in adjacent
nerve fibers; converge to form the auditory nerve

Hearing: The Structure of the Ear
Hearing: Pitch Perception
 Place Theory
 In hearing, the theory
that links the pitch we
hear with the place where
the cochlea’s membrane
is stimulated


We hear different pitches
because different sound waves trigger activity at
different places along the cochlea’s basilar membrane
Best explains our perception of high-pitched sounds
Hearing: Pitch Perception
 Frequency Theory
 In hearing, the theory
that the rate of nerve
impulses traveling up
the auditory nerve matches
the frequency of a tone, thus enabling us to sense its
pitch
 Best explains our perception of low-pitched sounds
Hearing: Sound Localization
Hearing: Hearing Problems
 Conduction Hearing Loss
 Caused by damage to the mechanical system that
conducts sound waves to the cochlea
 Sound vibrations cannot be passed from the eardrum
to the cochlea

Example
 Punctured eardrum
 Sensorineural Hearing Loss
 Caused by damage to the cochlea’s receptor cells or to
the auditory nerves

Also called nerve deafness
NERVE
DEAFNESS
CONDUCTION
DEAFNESS
Sensation:
The Other Senses
PART THREE
Sensation: Olfaction (Chemical Sense)
TO DISCUSS
• General structure
• Chemical sense
• Gender differences
• Connection to
limbic system
Sensation: Gustation (Chemical Sense)
TO DISCUSS
• Crudest sense
• General structure
• Chemical sense
• Average adult?
• Lifespan?
• Supertasters
• Gender differences
Instructions: Jelly Belly Activity
 In partners, you will take turns eating Jelly
Bellies…

Instructions for the EATER
The eating partner MUST keep his or her eyes closed
 The eating partner MUST keep his or her nose plugged
for the first few “chews”
 After 4-5 good chews, the eating partner should release
his or her nose


Instructions for the NON-EATER

The non-eating partner should provide the eating partner
with a Jelly Belly & silently note its flavor
Sensation: Skin (Somesthetic Sense)
TO DISCUSS
• General structure
• Pressure?
• Other sensations?
• Sensation of pain
• Gate Control Theory
• Fast v. Slow Fibers
Sensation: Kinesthetic (Somesthetic)
TO DISCUSS
• General structure
• Position & motion
sensors
Sensation: Vestibular (Somesthetic)
TO DISCUSS
• General structure
• Semicircular canals
• Otolith organs
• Planes of movement