Psych 120
General Psychology
Christopher Gade
Office: 1030A
Office hours: MW 4:30-5:30
Email: gadecj@gmail.com
Class MW 1:30-4:30 Room 2240
Sensation and Perception



Sensation: the conversion of energy from
the environment into a pattern of
responses by that nervous system.
Perception: the interpretation of that
information.
In order to understand our perception of
information, we first need to understand
how we are sensing that information.
Why Study Vision First?
1.
2.
3.
Vision is the most widely studied topic in
neurobiology and cognitive psychology.
Vision is critical to the human being’s
experience. In fact, approximately 25% of our
cognitive resources are reserved for that sense
alone.
We know a lot more about the eye than any
other sense organ, and we are significantly
closer to understanding vision that we are to
understanding any other sensation.
What Exactly Do We See?


Light is composed of pulses of electromagnetic
energy that vary in both wavelength and
amplitude.
The wavelength (i.e. frequency) of the light
pulse is what determines the hue (color) of the
light wave.
• Humans are able to see light on a range
of 400 to 700 nanometers (nm). Other
animals have sensitivity at different
wavelength ranges.
What Exactly Do We See (cont.)?

The amplitude of
the
electromagnetic
wave is what
determines the
intensity
(brightness) of
the light.
The Structure of the Eye

The Pupil: a small adjustable opening in
the eye, through which light enters.
The Structure of the Eye

The Iris: a colored adjustable muscle on the
surface of the eye that is responsible for
controlling the amount of light that enters the
eye through the pupil.
The Structure of the Eye

The Cornea: A rigid, protective surface on
the outer surface of the eye that focuses
light toward the fovea.
The Structure of the Eye

The Lens: A clear, flexible structure located
behind the cornea that can vary in thickness (to
help us focus on information at different
depths), and focuses the incoming light rays into
an image on the back of our eyes.
Interesting Fact

The lens of our eyes actually flips the image
that we are viewing. Our brains have to
eventually take that flipped information and
transform it in order for it to make sense.
The Structure of the Eye

The Vitreous Humor: a clear jelly-like
substance that light passes through on
its way to the retina.
The Structure of the Eye

The Retina: The multilayered tissue
located on the back of the eye that is
responsible for the transference of light
rays into neural information.
The Structure of the Eye

The Fovea: the central area of the
retina that is highly adapted for
detailed vision.
The Structure of the Eye

Rods and Cones: Specialized visual receptors
located along the retina. These neurons
transfer the sensory information into neural
impulses that are sent along the optic nerve.
Rods and Cones (cont.)
-Rods: receptors that are adapted for vision in dim
light. Their primary purpose is to detect motion.
-Cones: receptors adapted for color vision, daytime
vision, and detailed vision. The fovea contains only
cones.
-Rod and Cone Example
The Structure of the Eye

The Optic Nerve: a collection of cells that
is responsible for carrying the information
processed by your eye to the brain.
The Path of Vision (After the Eye)
Visual Sensation
Color:
•
wavelength and amplitude characteristics of emr correspond to
different colors and brightness of light (and sound…).
Color Sensation
The Young-Helmholtz/trichromatic theory.
•
•
Proposes that our receptors respond to three primary colors: blue,
green and red.
“Color vision depends on the relative rate of response by the three
types of cones.”, I.e. the combination of different levels of firing in
each type of cone gives rise to the broad spectrum of colors
perceived.
Visual Sensation
Color:
•
•
What about yellow, white, and black?
What about negative afterimages?
The Opponent Process Theory:
•
We sense color not in terms of
separate categories but rather in a
system of paired opposites: red
vs. green, blue vs. yellow and
black vs. white.
“ON”
red
green
blue
yellow
black
white
“OFF”
green
red
yellow
blue
white
black
The Interpretation of Colors and Patterns

The Brightness Contrast
• Method of determining the colors of objects (going beyond
just the frequency of the electromagnetic waves).
• The brightness of surrounding objects influences our
perception of the color and brightness of an object.
Visual Sensation
The Retinex Theory:
•
The Cerebral Cortex also plays a role in how we experience
color, I.e. color constancy, by comparing different patterns
of light from different areas of the retina.
Perception and Gestalt Psychology



Knowing the visual
system is great if
we want to know
about the basics of
vision.
But what about
interpretation?
How do we make
sense of
ambiguous stimuli?
Gestalt and
perception
psychology address
this problem.
Gestalt Psychology (cont.)



Gestalt psychology is
a field that focuses on
our ability to perceive
overall patterns.
“The whole is
different (and often
greater) than the sum
of its parts”.
Our perception is
based on our
attempts to create
semblance out of the
mess of stimuli that
we are presented
with.
Tricks to Determining
Distance/Depth

Binocular Cues (two eyes)
• Retinal disparity: the
position of an object is
determined by the
different signals received
by the two eyes.
• Convergence: the
distance of an object is
determined by the
amount of eye
movement required to
focus on an object.
Monocular Cues (two eyes are not required)



Object size (relative
size): nearer objects
look bigger.
Accommodation: Our
brains can detect how
much the lens of the
eye needed to shift in
order to focus on an
object.
Detail (relative clarity):
more detail signifies a
closer object.
Visual Illusions



So we interpret stimuli in our world
to make sense of it… great. Is there
any situations where this comes at a
cost?
Most of the time, this translation of
information is very useful for our
interaction with the real world.
But sometimes, there are situations
that trick the mind.
The Muller-Lyer Illusion
Depth Perception Illusions
The Ponso Illusion
The
Moon
Illusion
The Ames Room
The Other Senses:
Hearing
The properties of sound and
the basics of the ear.
Listening Exercise

Put your books, pens, pencils,
phones, and all other items down.

Close your eyes.

Listen!

What is it that you’re hearing?
Life Without Hearing



What are some of the things that we
would miss out on if we couldn’t
hear?
What are some of the things that we
would miss out on if we couldn’t see?
Which would you rather lose, hearing
or vision? Why?
Is Hearing Physical or Perceptual?



Physical Definition of
Sound: A change in
pressure of the air or
other physical medium.
Perceptual Definition of
Sound: An experience of
“sound waves” by the ear
or other perceptual
medium.
Sound Properties
• Sound Wave: A sudden
change in MOLECULE
pressure
• Boat Example
More Properties of Sound

Amplitude:
The
concentration
of the air
pressure.
Determines
the
“loudness” of
the sound.
• Decibel =
20log(p/po)
(po= pressure
medium for
air, it = 20)
More Properties of Sound

Frequency: The
rate of sound
wave
occurrences.
Determines the
“pitch” of the
sound.
• Sound
frequency
is measured by
Hertz (Hz). 1
Hz =1 cycle per
second.
The
Equal
Loudness
Curve
and
Audibility
Curve
What’s the
loudness
button on
your stereo
doing?
The Ear, Our Sound Wave Detector
The Inner Ear
The Other Senses: Touch
Reviewing the Timing Exercise

Looking back at how
long it took for us to
complete two tasks.
• Toe bumping
• Hand touching

The toe bumps took
longer because of
the path that
neurons need to
take is longer for
this communication.


Epidermis &
Dermis
Mechanoreceptors
• Merkel’s disks
(receptors)

Touch
• Meissner’s
corpuscles

Sense of grip
• Ruffini’s endings
(cylinders)

stretch
• Pacinian
corpuscles

vibration
The Skin
More on the Somatosensory Area

Area specificity
• The homunculus
and region focus
• The relationship
between cell
focus and brain
area coverage

The effects of
learning and
experience on
these areas
(reading by
touch, music,
video games)
Anatomy of Touch on the Brain
The Other Senses: Taste and
Smell?

Ugh, there’s no way we’ll have time
for this. Please make sure to read
about these two senses and how the
body detects molecules in these
ways. Its really interesting, but we
just don’t have time for it…