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)
What makes up a light wave?
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
Why do we have 2 ears?
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
Why do we study smell and taste together?
 SENSORY INTERACTION: the principle that one
sense may influence another.
Sensation: Olfaction (Chemical Sense)
Cilia
• Receptor cells that collect
molecules of odor.
Olfactory bulbs
• Receives an electrical signal and
generates a “code” that is sent to
the brain for interpretation.
• We can detect over 10,000 odors
and odors have the power to
evoke memories and feelings!
So can we smell a difference between
men & women?
Well….yes and no.
 Pheromones
 Chemicals excreted by humans and other animals that act
as signals to, and elicit certain patterns of, behavior from
members of the same species.

Used by animals to mark off territories and to signal
sexual receptivity.
 Karl Grammer
 Suggested that humans, although not consciously aware of
it, respond to pheromones when it comes to mating.
Sensation: Gustation (Chemical Sense)
We have bumps on our tongue called
papillae.
Taste buds are located on the
papillae.
Sweet, salty, sour, bitter and recently
umami (savory).
Bitterness detectors – critical because
most poisons are bitter.
Sour detectors – detect bad foods.
Built-in salt and sugar needs for
survival
Sensation: Skin (Somesthetic Sense)
 Receptors located in our skin
 Three types of touch
 Pressure
 Pain
 Temperature
 Gate control theory -
Contends that there is an area
in the spinal cord that can act
like a “gate” and either inhibit
pain messages or transmit
them to the brain
Phantom Limb Pain
• Phantom limb pain is a
frequent complication of
amputation.
• Client complains of pain at
the site of the removed
body part, most often
shortly after surgery.
Sensation: Kinesthetic (Somesthetic)
• Tell us where are body
parts are
• Receptors are located
in our
• Muscles
• Joints
• Tendons
Sensation: Vestibular (Somesthetic)
• Tells us where our body is orientated in space
• Our sense of balance
• Located in our semicircular canals in our ears