Sensory and Perception
Chapter 3
Exploring Psychology
Helen Keller had been blind and deaf since she was
two years old. For the next four years, Helen was “wild
and unruly.” Then when she was six, Anne Sullivan, a
teacher, entered her life. Using the sense of touch as
the link between their two worlds, Anne tried again and
again, by spelling words into Helen’s hand, to make
Helen grasp the connections between words and the
things they stood for. The breakthrough came one day
as Anne spelled the word water into Helen’s hand as
water from a spout poured over it. “I stood still, my whole
attention fixed upon the motions of her fingers,” Helen
remembered. “Suddenly I felt…a thrill of returning thought;
and somehow the mystery of language was revealed to
me.” adapted from ABC’s of the Human Mind, Reader’s Digest, 1990.
Helen Makes a Breakthrough
4:16
The Questions
• What senses were unavailable to Helen
Keller?
• How did she learn to compensate?
An Eskimo or Native American?
What’s Up?
• In the next few seconds, something
peculiar will start hap pening to the
material youa rereading. Iti soft ennotre
alieze howcom plext heproces sof rea ding
is.
Can You Read This???
• Aoccdrnig to a rscheearch at Cmabrigde
Uinervtisy, it deosn’t mttaer in what oredr
the ltteers in a word are, the olny iprmoetnt
tihng is that the frist and lsat ltteer be at
the rghit pclae. The rset can be a toatl
mses and you can still raed it wouthit
porbelm. This is bcuseae the huamn mnid
deos not raed ervey lteter by istlef, but the
word as a wlohe.
What is sensation?
• What occurs when a stimulus activates a
receptor.
• Stimuli - any change in the environment to
which an organism respond.
• Stimulus  Response
What is a perception?
• Combined sensations with past experiences.
• How we, as INDIVIDUALS, interpret out
sensations.
• Organization of sensory information into
meaningful experiences.
Who is this a picture of?
Psychophysics
• The study of the relationships between
sensory experiences and the physical
stimuli that caused them.
– How much energy is required for someone to hear a
sound or see a light?
– How much of a scent must be in a room before one
can smell it?
Absolute Threshold
• The point where something becomes
noticeable to our senses.
• The absolute threshold is therefore the
point at which a stimuli goes from
undetectable to detectable to our senses.
• A person can detect the stimulus 50% of
the time.
The Absolute Thresholds…
• Vision – a candle flame 30 miles away on
a clear night.
• Hearing – hearing a watch ticking 20 feet
away.
• Taste – tasting 1 teaspoon of sugar
dissolved in 2 gallons of water.
• Smell – smelling 1 drop of perfume in a 3room house.
• Touch – feeling a bee’s wing falling a
distance of 1 centimeter onto your cheek.
Sensory Adaptation/
Difference Threshold
• Allows us to notice differences in sensations and
react to the challenges of different or changing
stimuli.
• Our senses adjust to the overall level of
stimulation.
• The difference threshold is the amount of
change needed for us to recognize that a
change has occurred.
• More stimulation, less sensitive.
• Less stimulation, more sensitive.
This difference is not absolute, however…
• Imagine holding a five pound weight and one
pound was added. Most of us would notice this
difference. But what if we were holding a fifty
pound weight? Would we notice if another
pound were added? The reason many of us
would not is because the change required to
detect a difference has to represent a
percentage. In the first scenario, one pound
would increase the weight by 20%, in the
second, that same weight would add only an
additional 2%. This theory, named after its
original observer, is referred to as Weber's Law.
Weber’s Law
• What is Weber’s Law?
– States that for any change (▲s) in a stimulus
to be detected, a constant proportion of that
stimulus (s) must be added or subtracted.
INTERFERENCE
“The Stroop Effect”
Red
Yellow
Green
Blue
Red
http://faculty.washington.edu/chudler/words.html
The Five Senses
Or NOT
The Sense Song
1:28
Senses
•
•
•
•
•
•
Seeing
Hearing
Smelling
Tasting
Touching
Internal
– Vestibular
– Kinesthetic
The Sixth Senses
• Vestibular
– Three semicircular canals located in the inner
ear that provide a sense of balance.
• Kinesthetic
– The sense that provides information about the
position and movement of individual body
parts.
The Eyes
• Light = Stimulus for sense of sight.
– Light enters the eye through the cornea.
– Passes through the pupils (contracts).
– Moves through a lens and focuses on the retina
(lining of the eye containing the receptor cells)
– Fovea is the part of the eye that focuses images.
• Color Deficiency
– Being color blind.
• Binocular Fusion
Color Vision
• Trichromats
– people with normal color vision.
• Monochromats
– most severe type of colorblindness (less
common)
• Dichromats
– blind to either red-green or blue-yellow
shades of light and dark (more common).
Sight
3:47
Hearing
• Auditory nerve
– Loudness – determined by the amplitude of
the sound wave.
– Pitch – determined by the frequency of the
sound wave (vibration).
Deafness
• Types:
– Conduction
• Occurs when anything hinders physical motion
through the outer or middle ear or when the bones
of the middle ear become rigid and cannot carry
sound.
• Usually a hearing aid will help.
– Sensorineural
• Occurs from damage to the cochela, the hair cells,
or the auditory neurons.
• A cochlear implant will be needed to hear sound.
Hearing
The Olfactory Nerve
Smell
1:27
What Makes Up Taste?
•
•
•
•
Sour
Salty
Bitter
Sweet
• Flavor = taste, smell and tactile
sensations.
Taste
1:19
The Skin Senses
• Four kinds of information:
– Pressure
– Warmth
– Cold
– Pain
• Gate control theory of pain
– Lessen some pain by shifting the attention away from the pain
impulses.
Touch
2:06
Senses are Sensational
0:58
Perception
Trying to Catch a Fly
• The frog’s bug detector shows the rigidity of reflexive
behavior. If you sever the frog’s optic nerve, it will grow
back together, and the bug detector will still work fine. If
you sever the optic nerve and then rotate the frog’s eye
180 degrees, the nerve will still heal and reestablish all
the old connections; however, this time the results will
not be so good. The bug detector does not know that
everything has been rotated, so it miscomputes a bug’s
location. If the bug is high, the frog shoots its tongue
low. If the bug is to the right, the tongue goes to the left.
The frog never learns to compensate for the changed
situation.
from A Second Way of Knowing: The Riddle of Human Perception by
Edmund Blair Bolles, 1991
The Question
• Where does perception occur: in the
sensory organ, in the nerve, or in the
brain?
Perception
• The brain receives information from the
senses and organizes and interprets it into
meaningful experiences – unconsciously.
• Each whole that is organized by the brain
Gestalt
is called a _________
Principles that people use in
organizing such patterns:
• Proximity
– When we see a number of similar objects, we tend to perceive
them as groups or sets of those that are close to each other.
• Continuity
– We tend to see continuous patterns, not disrupted ones.
• Similarity
– When similar and dissimilar objects are mingled, we see the
similar objects as groups.
• Simplicity
– We see the simplest shapes possible.
• Closure
– When we see a familiar pattern or shape with some missing
parts, we fill in the gaps.
Figure-Ground Perception
• The ability to discriminate properly
between a figure and its background.
Perceptual Inference
• Filling in the gaps.
Subliminal Perception
• Subliminal perception occurs whenever
stimuli presented below the threshold of
awareness are found to influence
thoughts, feelings, or actions.
Food Network
Depth Perception
• Monocular Depth Cues
– Used to perceive distance and depth.
– Can be perceived with only one eye.
• Binocular Depth Cues
– Depends upon the movement of both eyes.
Constancy
• The tendency to perceive certain objects
in the same way regardless of changing
angle, distance, or lighting.
Illusions
• Perceptions that misrepresent physical
stimuli.
• They are created when perceptual cues
are distorted so that our brains cannot
correctly interpret space, size, and depth
cues.
Extrasensory Perception
• An ability to gain information by some means
other than the ordinary senses.
• Four Types:
– Clairvoyance
• perceiving objects of information without sensory input.
– Telepathy
• involves reading someone else’s mind or transferring one’s
thoughts
– Psychokinesis
• involves moving objects through purely mental effort
– Precognition
• the ability to foretell events.
More Than Meets the Eyes
18:48