Sensory Deprivation and Restored
Perception and the Human Factor
Is There Extrasensory Perception?
Claims of ESP
Premonitions or Pretensions?
Putting ESP to Experimental Test
Sensation & Perception
How do we construct our representations of the
To represent the world, we must detect physical
energy (a stimulus) from the environment and
convert it into neural signals. This is a process
When we select, organize, and interpret our
sensations, the process is called perception.
Analysis of the stimulus begins with the sense
receptors and works up to the level of the brain
Letter “A” is really a black blotch broken down into
features by the brain that we perceive as an “A.”
Information processing guided by higher-level
mental processes as we construct perceptions,
drawing on our experience and expectations.
Our sensory and perceptual processes work
together to help us sort out complex images.
Making Sense of Complexity
“The Forest Has Eyes,” Bev Doolittle
Sensing the World
Senses are nature’s gift that suit an organism’s
A frog feeds on flying insects; a male silkworm
moth is sensitive to female sex-attractant odor; and
we as human beings are sensitive to sound
frequencies that represent the range of human
Exploring the Senses
What stimuli cross our threshold for
A study of the relationship between physical
characteristics of stimuli and our psychological
experience with them.
Absolute Threshold: Minimum stimulation needed
to detect a particular stimulus 50% of the time.
0 5 10 15 20 25
Stimulus Intensity (lumens)
When stimuli are below
one’s absolute threshold for
Two stimuli must differ by a constant minimum
percentage (rather than a constant amount), to be
perceived as different. Weber fraction: k = δI/I.
Stimulus Constant (k)
Diminished sensitivity as a consequence of
Put a band aid on your arm and after awhile
you don’t sense it.
Parts of the eye
1. Cornea: Transparent tissue where light enters
2. Iris: Muscle that expands and contracts to
change the size of the opening (pupil) for light.
3. Lens: Focuses the light rays on the retina.
4. Retina: Contains sensory receptors that process
visual information and sends it to the brain.
structure behind the
pupil that changes shape
to focus images on the
process by which the
eye’s lens changes shape
to help focus near or far
objects on the retina.
Retina: The light-
surface of the eye,
rods and cones in
addition to layers of
cells) that process
Optic Nerve, Blind Spot & Fovea
Optic nerve: Carries neural impulses from the eye to the
brain. Blind Spot: Point where the optic nerve leaves the
eye because there are no receptor cells located there.
Fovea: Central point in the retina around which the eye’s
Test your Blind Spot
Use your textbook. Close your left eye, and fixate
your right eye on the black dot. Move the page
towards your eye and away from your eye. At
some point the car on the right will disappear due
to a blind spot.
Bipolar & Ganglion Cells
Bipolar cells receive messages from
photoreceptors and transmit them to ganglion
cells, which converge to form the optic nerve.
Visual Information Processing
Optic nerves connect to the thalamus in the
middle of the brain, and the thalamus connects to
the visual cortex.
Nerve cells in the visual cortex respond to
specific features, such as edges, angles, and
Specific combinations of temporal lobe activity
occur as people look at shoes, faces, chairs and
Visual Information Processing
Processing of several aspects of the stimulus
simultaneously is called parallel processing. The
brain divides a visual scene into subdivisions such
as color, depth, form, movement, etc.
Trichromatic theory: Young and von Helmholtz
suggested that the eye must contain three receptors
that are sensitive to red, blue and green colors.
Blue Green Red
Genetic disorder in which people are blind to
green or red colors. This supports the
Gaze at the middle of the flag for about 30
Seconds. When it disappears, stare at the dot and report
whether or not you see Britain's flag.
Outer Ear: Collects and sends sounds to the
Middle Ear: Chamber between eardrum and
cochlea containing three tiny bones (hammer,
anvil, stirrup) that concentrate the vibrations
of the eardrum on the cochlea’s oval window.
Inner Ear: Innermost part of the ear,
containing the cochlea, semicircular canals,
and vestibular sacs.
Cochlea: Coiled, bony, fluid-filled tube in the
inner ear that transforms sound vibrations to
Amount of energy
in a wave,
determined by the
to the perceived
Loudness of Sound
The dimension of
determined by the
distance from the
peak of one wave
to the peak of the
Localization of Sounds
Because we have two ears, sounds that reach
one ear faster than the other ear cause us to
localize the sound.
Localization of Sound
1. Intensity differences
2. Time differences
Time differences as small as 1/100,000 of a second
can cause us to localize sound. The head acts as a
“shadow” or partial sound barrier.
The sense of touch is a mix of four distinct skin
senses—pressure, warmth, cold, and pain.
Only pressure has identifiable receptors. All other
skin sensations are variations of pressure,
warmth, cold and pain.
Pressure Vibration Vibration
Cold, warmth and pain
Pain tells the body that something has gone
wrong. Usually pain results from damage to the
skin and other tissues. A rare disease exists in
which the afflicted person feels no pain.
Ashley Blocker (right) feels neither pain
nor extreme hot or cold. APPhoto/StephenMorton
Traditionally, taste sensations consisted of sweet,
salty, sour, and bitter tastes. Recently, receptors for
a fifth taste have been discovered called “Umami”.
Sweet Sour Salty Bitter Umami
When one sense affects another sense, sensory
interaction takes place. So, the taste of strawberry
interacts with its smell and its texture on the
tongue to produce flavor.
Like taste, smell is a chemical sense. Odorants
enter the nasal cavity to stimulate 5 million
receptors to sense smell. Unlike taste, there are
many different forms of smell.
Smell and Memories
The brain region for
smell (in red) is closely
connected with the
brain regions involved
with memory (limbic
system). That is why
strong memories are
made through the sense
Body Position and Movement
The sense of our body parts’ position and
movement is called kinesthesis. The vestibular
sense monitors the head (and body’s) position.
Whirling Dervishes Wire Walk
How do we form meaningful perceptions
from sensory information?
We organize it. Gestalt psychologists
showed that a figure formed a “whole”
different than its surroundings.
Depth perception enables us to judge distances.
Gibson and Walk (1960) suggested that human
infants (crawling age) have depth perception. Even
newborn animals show depth perception.
Retinal disparity: Images from the two eyes differ. Try
looking at your two index fingers when pointing them
towards each other half an inch apart and about 5 inches
directly in front of your eyes. You will see a “finger
sausage” as shown in the inset.
Relative Size: If two objects are similar in size, we
perceive the one that casts a smaller retinal image
to be farther away.
Interposition: Objects that occlude (block) other
objects tend to be perceived as closer.
Relative Height: We perceive objects that are higher in our
field of vision to be farther away than those that are lower.
Relative motion: Objects closer to a fixation point
move faster and in opposing direction to those
objects that are farther away from a fixation point,
moving slower and in the same direction.
Perceiving objects as unchanging even as
illumination and retinal images change.
Perceiving familiar objects as having consistent
color even when changing illumination filters
the light reflected by the object.
The distant monster (below, left) and the top red
bar (below, right) appear bigger because of
Both girls in the room are of similar height.
However, we perceive them to be of different
heights as they stand in the two corners of the
Both photos from S. Schwartzenberg/ The Exploratorium
The Ames room is designed to demonstrate the size-
The color and brightness of square A and B are the same.
Immanuel Kant (1724-1804) maintained that
knowledge comes from our inborn ways of
organizing sensory experiences.
John Locke (1632-1704) argued that we learn to
perceive the world through our experiences.
How important is experience in shaping our
Sensory Deprivation & Restored
After cataract surgery,
blind adults were able
to regain sight. These
differentiate figure and
yet they had difficulty
distinguishing a circle
and a triangle
(Von Senden, 1932).
After blind adults
regained sight, they were
able to recognize distinct
features, but were unable
to recognize faces.
Normal observers also
show difficulty in facial
recognition when the
lower half of the pictures
without exposure to
horizontal lines later
Blakemore & Cooper (1970)
Visual ability to adjust
to an artificially
displaced visual field,
e.g., prism glasses.
A mental predisposition to perceive one thing
and not another. What you see in the center
picture is influenced by flanking pictures.
(a) Loch ness monster or a tree trunk;
(b) Flying saucers or
Other examples of perceptual set.
Is the “magician cabinet” on the floor or hanging from the
Context can radically alter perception.
To an East African, the woman sitting is balancing a metal
box on her head, while the family is sitting under a tree.
Context instilled by culture also alters
Is perception innate or acquired?
Is There Extrasensory Perception?
Perception without sensory input is called
extrasensory perception (ESP). A large percentage
of scientists do not believe in ESP.
Claims of ESP
1. Telepathy: Mind-to-mind communication. One
person sending thoughts and the other
2. Clairvoyance: Perception of remote events,
such as sensing a friend’s house on fire.
3. Precognition: Perceiving future events, such as
a political leader’s death.
The power of “mind over matter” such as
levitating a table/influencing a role of the die.