sensation and perception.pptx .....,,,,,,,,,,,,

Sensation
+
Meanings
+
Thinking
+
Memory
= “Perception”
Wundt
Regards:

Sensation, Perception
Sensation is the activation of receptors by stimuli in the
environment.
Sensations are the basic building blocks of perception.
Perception is the process of organizing and attempting to
understand the sensory stimulation we receive.
To activate a particular receptor, a specific type of energy
must be present—light waves for vision, movement of air
molecules for hearing, molecules in a liquid solution for
taste, and so forth

Transduction is the process by which the receptors
change the energy they receive into a form that can be
used by the nervous system.
Adaptation occurs when continued presentation of the
same stimulus results in a loss of sensitivity to that
stimulus.

Sensory Systems
Vision is a process that involves the reception of
electromagnetic waves by visual receptor cells.
This kind of energy travels in waves that vary greatly in
length.
We measure wavelengths, or the length of waves, in
nanometers (nm), which are billionths of a meter.
The only light waves that humans can detect have wavelengths
between approximately 380 and 760 nm.
This limited range of stimuli (the human eye can see only a
small portion of the spectrum) is called the visible spectrum.
Different light wavelengths are associated with different
colors.

Amplitude refers to the strength or intensity
(brightness) of the light.
Saturation refers to the “trueness” or purity of
the colors we perceive.
With radiant light, visible energy is emitted
(released) directly by an object.
With reflected light, by contrast, energy is reflected
by objects

If a surface reflects only one wavelength, the color you
perceive is pure.
The degree of purity decreases as the number of
different, reflected wavelengths increases.
Vision involves a complex chain of events.
Initially, light waves pass through the protective cornea.
In addition to its protective function, the cornea helps
focus the light waves.
After striking the cornea, light waves enter an open area
called the anterior chamber.
Here they pass through the aqueous humor, a clear
watery fluid.
Then the light waves are funneled through the small
opening known as the pupil.

The pupil is surrounded by a colored membrane, the iris,
which changes shape (like the diaphragm of a camera) to
regulate the size of the pupil and therefore the amount of
light taken in.
Next, the light passes through the lens.
The lens, which is supported by two powerful ciliary
muscles, is elastic; it can change shape to focus the visual
image.
Changing the shape of the lens to focus is known as
accommodation.
After passing through the lens, the light waves enter a
second, larger open space called the posterior chamber.
Finally, the light waves strike the retina, the light-
sensitive tissue at the back of the eye that contains the
visual receptors (rods and cones).

The retina is made up of several layers: the three major
layers are the ganglion cell layer, the bipolar cell layer,
and the photoreceptor layer.
After light strikes the surface of the retina, it must travel
through several layers of cells before it activates the
visual receptors, which make up the back layer of the
retina.
Light waves cause the receptors to change their
electrical charge.
If that change is great enough, the bipolar cells fire.
If enough bipolar cells fire, the next layer of cells, the
ganglion cells, fires.

3-13
Layers of Cells in the Retina

The axons of the ganglion cells come together to form the
optic nerve, which carries visual information to higher brain
centers.
At the point where the axons of the ganglion cells come
together and leave the eyeball, there are no receptors.
This area is known as the blind spot.
The optic nerves from each eye join at the optic chiasm,
which is located on the underside of the brain, just in front of
the pituitary gland.
The fibers from the nasal half (closest to the nose) of the
retina cross to the opposite hemisphere; those from the
peripheral (outlying) half of each retina continue to the
hemisphere on the same side of the body.
The next stop is an area in the thalamus, the relay station in
the forebrain.

Ultimately, the visual information is received by the
occipital lobe of the cortex, where higher-level visual
processing begins.
The rods (120 to 125 million per eye) are the most
prevalent visual receptors.
They have a lower threshold and lower acuity
(sharpness of perception) than cones and do not detect
color.
By contrast, the cones (6 to 7 million) are less
prevalent, have a higher threshold and higher acuity,
and are able to detect color.
The rods are slender and cylindrical, whereas the
cones are much broader.
Most of the cones are found in one area, the fovea, an
indented spot in the center of the retina. Both the rods
and cones contain light-sensitive chemicals called
photopigments.

The Visual Pathway

Two theories of color vision have been formulated.
The trichromatic theory proposes that there are three different
types of color receptors.
The opponent-process theory stresses the pairing of color
experiences; activation of one process can inhibit its partner.
Both theories are supported by research findings.
Opponent-process cells may also be responsible for the
production of color afterimages.
A color afterimage is the perception of a color that is not
really present; it occurs after viewing the opposite or
complementary color.
People who suffer deficits in color vision are said to be color
deficient.
Monochromats are unable to see color.
Dichromats lack the ability to see one of the
three primary colors (red, blue, or green).

Audition is the sense of hearing.
Just as we see light waves, we hear sound waves.
A sound wave is essentially moving air.
Like light waves, sound waves have three distinct
characteristics: wavelength (frequency), amplitude
(intensity), and purity (also known as timbre).
Frequency is measured in cycles per second and
expressed in hertz (Hz).
As with light waves, the amplitude, or height, of the
sound wave affects its intensity.
Greater amplitude results in a more intense sound.
The amplitude of sound waves is measured in decibels
(db).

Sound Waves

Decibel levels represent the amount of energy producing
the pressure of the vibrations we perceive as sound; the
greater the pressure, the stronger or more intense the
vibration.
The purity or timbre of a sound wave can be measured, but
we do not experience many pure tones in our lifetimes.
Like the visual receptors, the auditory receptors are
sensitive to a limited range of sound waves.
Basically, we hear sounds with wavelengths between 20
and 20,000 Hz.
Our hearing is more acute at 1,000 Hz; greater intensity
(amplitude) is required if we are to hear tones at lower and
higher frequencies.

The auditory system is divided into three components: the
outer ear, the middle ear, and the inner ear.
The outer ear, especially the pinna, gathers sound waves
and starts them on their way to the auditory receptors.
The sound waves are then funneled down the auditory
canal.
Ultimately they strike the eardrum and cause it to move.
Movement of the eardrum in turn causes the three bones
(hammer, anvil, and stirrup) of the middle ear, collectively
called the ossicles, to vibrate.
The hammer (malleus), which is attached to the eardrum,
strikes the anvil (incus).
The anvil in turn strikes the stirrup (stapes).

The Auditory System

The stirrup is connected to the oval window, which connects
the middle ear to the snail-shaped cochlea of the inner ear.
When the stirrup causes the oval window to vibrate, fluid
located in the cochlea is set in motion.
The motion of the fluid produces vibration in the basilar
membrane.
This vibration in turn causes the organ of Corti, which rests
on it, to rise and fall.
When the organ of Corti moves upward, the hair cells that
project from it brush against the tectorial membrane
located above it.
The hair cells are the auditory receptors where transduction
occurs.
Contact with the tectorial membrane causes them to bend;
when they bend, they depolarize.

Sufficient depolarization of the auditory receptors causes
the neurons that synapse with them to fire.
The axons of these neurons come together before they
leave the cochlea to form the auditory nerve, which
transmits auditory information to higher brain centers.
From the cochlea, the auditory nerve travels to the
medulla, where some fibers cross to the opposite
hemisphere.
The next stop is the thalamus.
Ultimately the information reaches the temporal lobe of
the cortex for processing.

Gustation refers to the sense of taste.
The stimuli for taste are molecules dissolved in a liquid.
Once molecules are in solution, they can come into contact
with the taste receptor cells, which are located in structures
known as taste buds.
Each taste bud contains between 50 and 100 taste
receptors.
The taste buds line the walls of small bumps on the tongue
and throat called papillae.
Individual taste receptor cells do not last forever; with a life
expectancy of only 10 days to 2 weeks, the cells within a
taste bud are continually being replaced.
The number of taste buds increases during childhood to a
maximum of about 10,000.
At approximately age 40 the trend reverses and our sense of
taste declines.

Olfaction

Olfaction refers to the sense of smell.
Odors are produced by molecules in the air.
More than 2 million Americans have a significant loss in the
ability to smell.
This condition, called anosmia, can result from genetic
defects, aging, viruses, allergies, or certain prescription
drugs.
The most common cause, however, is head trauma, which can
shear off axons that run from the olfactory nerves to the
brain.
The nose does not contain the olfactory receptors; its function
is to collect and filter the air we breathe.
The olfactory receptors are located in an area of tissue of
about 2.5 cm (1 in.) square in each nasal cavity.
We have about 10 million olfactory receptors, each of which
has 6 to 12 hair-like projections called cilia.

Like taste receptors, olfactory receptors are continually
dying and being replaced.
The life span of an olfactory receptor is about 5 to 8 weeks.
There may be as many as 1,000 different types of olfactory
receptor sites.
Although researchers do not know a great deal about how
they work, the olfactory receptors appear to operate under
the same type of lock-and-key/pattern recognition principle
as the taste receptors.
The olfactory nerve takes a somewhat different route to the
brain from the other senses.
The first step is a synapse in the olfactory bulb, which is
located near the optic chiasm on the underside of the brain.
From there, some of the olfactory nerve fibers go to the
amygdala.
From the amygdala, the olfactory nerve travels to the
thalamus and hypothalamus and then on to the cerebral
cortex for higher-level processing.

3-29
Sensory Systems
Cutaneous senses refers
to a system of receptors
located in the skin that
provides information
about touch, pressure,
pain, and temperature.

The kinesthetic sense is a system of receptors located in the
muscles and joints that provides information about the
location of the extremities.
Sense receptors located in the joints and muscles send
information to the brain concerning muscle tension and joint
position.
The brain combines this information with other sensory
input, such as vision and audition, to help you determine the
location of your limbs.
The wide variety of skin receptors for touch or pressure are
called mechanoreceptors; the receptors for temperature are
called thermoreceptors.
The general term for receptors that respond to painful
stimuli is nocio receptors.

The process by which sensory
information is actively organized and
interpreted by the brain
The process of selecting,
organizing, and interpreting raw
sensory data
into useful
mental
representations of the world.
PERCEPTION

sensation and perception.pptx .....,,,,,,,,,,,,

Perception
We do not perceive everything in our environment; our
motives greatly influence our perceptions.
Similarly, certain stimuli are more likely than others to
attract our attention.
In dichotic listening experiments, a different message is
presented to each of a participant’s ears, and the participant
is asked to recall both messages.
Dichotic listening tasks are designed to study divided
attention, the ability to attend to more than one message or
type of information at the same time.
Research in this area has uncovered some intriguing
information about human perception.
For example, we hear (and understand) much more than the
information of which we are consciously aware as illustrated
by the “cocktail-party phenomenon.”

In addition to needs, motives, and prejudices, certain aspects
of stimuli determine which ones get our attention.
For example, people generally pay more attention to stimuli
that are larger, louder, or more colorful than others.
When something happens unexpectedly, our attention is
attracted very quickly.
When contrast and surprise combine, our attention is
commanded even more quickly.
The ability to discriminate among shapes and figures is
known as pattern perception.
The feature analysis theory states that we perceive the
elements of an object and then combine them to produce our
perception of the object (bottom-up processing).
Research suggests that, at least in some instances, we use a
top-down approach in which the whole object is recognized
before its component parts are identified.

Perceptual Process
“ WE DON’T SEE THINGS AS THEY ARE,
WE SEE THINGS AS WE ARE ”
According to Udai Pareek, “perception can be defined as the
process of receiving, selecting, organizing, interpreting,
checking and reacting to sensory stimuli or data”.

Perceptual Process
Stimuli
Selection
Organization
Interpretation
Action

1. Receiving Stimuli
The perception process starts with the reception
of stimuli. The stimuli are received from the
various sources.
Through the five organs, we see things/objects,
hear sounds, smell, taste and touch things. In this
way, the reception of stimuli is a physiological
aspect of perception process.
Stimuli may be external to us (such as sound
waves) and inside us (such as energy generation
by muscles).

2. Selection of Stimuli
People, in their everyday life, They cannot assimilate all what
they observe or receive from the environment at a time.
• Hence, they select some stimuli for further processing to
attach meaning to them while the rest are screened out.
• Selection of stimuli is not made at random, but depending
on the two types of factors, namely external factors and
internal factors.
• While external factors relate to stimuli such as intensity of
stimuli, its size, movement, repetition, etc.
• internal ones relate to the perceiver such as his/her age,
learning, interest, etc.
• Normally people selectivity perceive objects or things which
they are indifferent. • This is also called ‘selective perception’.

3. Organisation of Stimuli
Having selected stimuli or data, these need to be organized
in some form so as to assign some meaning to them.
• Thus, organizing the bits of information into a meaningful
whole is called “organization”.
• There are three ways by which the selected data i.e., inputs
are organized.
These are:
a) Grouping • It is based on the similarity or proximity of
various stimuli perceived.
• The tendency to group stimuli. i.e., people or things
appearing similar in certain ways has been a common means
of organizing the perception.

b) Closure • When people face with incomplete
information, they tend to fill the gap themselves to make
it more meaningful.
• They may do it on the basis of their experience, guess,
or past data.
c) Simplification • When people find themselves
overloaded with information, they try to simplify it to
make it more meaningful and understandable.

4. Interpretation
The data collected and organized remain meaningless for
the perceiver till these are assigned meanings.
• Assigning meanings to data is called ‘interpretation’
• Halo Effect “ An effect whereby the perception of positive
qualities in one thing or part gives rise to the perception of
similar qualities in related things or in the whole.
• An example of the halo effect would be judging a good-
looking person as more intelligent. The term is commonly
used in human resources recruitment.
• It refers to the risk that an interviewer will notice a positive
trait in an interviewee and, as a result, will overlook their
negative traits.

• Attribution • Explaining human behavior in terms of cause
and effect is called ‘Attribution’.
• However, attributing casual explanation to a particular
human behavior sometimes tends to distort perception. •
Stereotyping • When individuals are judged on the basis of
the characteristics of the group to which they belong, this is
called ‘Stereotyping’. • e.g. ‘older workers cannot learn new
skills’• ‘Japanese are nationalistic’
• Situation • The situation or context in which we observe or
see things also influence our perception about them.
• Perceiver • The factors residing in the perceiver himself/her
self do also operate to shape and sometimes distort his/her
perception. • The perceiver attitude, motives, interests, past
experience, and expectations are among the more relevant
personal factors/characteristics that affect perception.

5. Action
• Action is the last phase in the perceptual
process.
• The action may be positive or negative
depending upon favorable perception held by the
perceiver

 Subjective factor.
 Objective factor.
 Social factor.
Factorof
perception:

Subjective factor are related to the perceiver's own
internal state
or
self. There are stated as
the psychological state.
Some subjective are:
 Fitness.
 Interest.
 Past experience and Knowledge.
 Mantel Capacity.
Subjective
Factor:

Objective factor are found in the physical
environment know as stimuli. There stimuli are so strong
that an individual is attracted to attend to them and
perceive them.
Objective
factor:

Social factor are related to need and interest of the
group in society to which an individual belongs. Men is a
social animal. He cant live alone
 Social value.
 Attitudes.
 Stereotype.
 Suggestion.
Social
Factor:

There are five kinds of perception
These are:
 Form Perception.
 Perception of Movement.
 Depth perception.
 Time Perception.
Kindsof
Perception:

Perception depends on sensory information's. On
the base of these information, different forms and
patterns are perceived.
According to wood worth, perceptual organization
is based on two thinks:
 Figure
 Ground
Form
Perception:

The Gestalt psychologists demonstrated that we actively
organize our perceptual world into meaningful groups or
wholes.
Figure–ground relation is the organization of perceptual
elements into a figure (the focus of attention) and a
background.
Several conditions promote the grouping of perceptual
elements are called Gestalt principle.
With proximity, items that are close to each other are
perceived as a group.
According to the Gestalt principle of similarity, items that
are alike are grouped together: XXXOOO, is perceived as
three Xs and three Os.

The Gestalt principle of good continuation says that we
perceive continuous, flowing lines more easily than choppy
or broken lines.
The Gestalt principle of closure says that organizing our
perceptions into complete objects is easier than perceiving
each part separately.
Apparent motion is the illusion of movement in a
stationary object.
Perceptual hypotheses are inferences about the nature of
stimuli received from the environment.
Perceptual illusions are misperceptions or interpretations
of stimuli that do not correspond to the sensations received.

 Law of Proximity or Nearness.
 Law of Similarity.
 Law of Good from or figure.
LawOfPerceptual
Organizations:

Proximity means nearness. According to this law,
the things situated nearer to each other; form a figure or
a pattern and are perceived as a whole figure. This
proximity may be in space and time. If different words are
set nearer to each other, they form an organization.
Consequently, we perceive them in a moment. As it is
evident from the following figure
LawsofNearnessor
proximity:

Our brain see objects near each other as groups.
Lawsof
proximity:

Law of similarity or likeness is the perceptual tendency to
group together similar elements. If different objects are similar in
shape, we classify them in a group; and perceive accordingly as
shown in fig:
Lawofsimilarityor
Likeness:

In the law of good form, the stimuli having stimuli
having similar ship are grouped together. This
group[ may b of five types
 Good Continuation
 Symmetry
 Closure
 Common Direction
 Inclusiveness
LawofGood
Form:

The perceptual tendency to see all the parts of a
figure in “one whole” is the whole good
called
picture of the grouping
continuation. It make
a organization.
Good
Continuation:

A symmetrical figure makes a
perceptual organization and perceived sooner.
In the following figures we perceived circles, areas
and lines as a single unit when uniformed and linked.
Symmetry
:

It is our perceptual tendency to fill the gaps or
closure fills the gaps in perceptual organization to help us
to perceive it as a whole complete form, for example the
following incomplete circle
Closure
:

When the stimuli are presented in a straight line or
a semi-circle form, their grouping in the perceptual
organization is classified in two groups because of their
common direction, for example
Common
Direction:

Sometimes all the stimuli are include to form a
pattern.
Due to this inclusiveness in the following lines of
similar pattern.
Inclusiveness
:

Movement or Motionis perceived by
following the progressive change of an object’s
position in space with time.
It has two types
 Real Movement:
 Apparent Movement:
Perceptionof
Movement:

Real
Movement:
The perception of the actual movement of objects
as “real motion/movement
in the world is termed
“perception”.
Apparent
Movement:
It is movement perceived in the absence of
physical movement of an image across the retina. This
can be produced by a rapid succession of motionless
stimuli that minimize the changes that occur in real
movement.

The ability to view the world in three
dimensions
and to perceive distance is known as depth perception.
“This ability helps to perceive three dimensional space
and to accurately judge distance”
Depth
Perception:

Depth perception
Two main types of cues, binocular and monocular, are
used to create our perception of depth.
Binocular cues require the integrated use of both eyes,
whereas monocular cues are effectively processed using
information from only one eye.
Two binocular cues are adjustments of the eye muscles
(a weak/non precise cue) and binocular disparity.

If you open and close one eye and then the other, it is obvious
that you do not see exactly the same thing with each eye.
The closer the object, the greater the difference between what
the two eyes see.
This difference occurs because each eye sees from a different
angle, a phenomenon known as binocular disparity.
When the images from both eyes merge in the brain, a sense
of depth is created.
Monocular cues of depth include
interposition (near objects partially obscure more distant
objects),
texture gradient (the texture of a surface becomes smoother
with increasing distance),
linear perspective (parallel lines appear to converge as they
recede into the distance), and
relative brightness (brighter objects appear closer than
duller-appearing ones).

We perceive time in, seconds, minutes, and hours
which pass into days weeks months and in years and even
in centuries. Time is perceived in terms of Past, Present,
and Future Perception of time is less in children than
elders Several factors influence time perception: Subjective
(age, activity, motivation, intelligence) Objective:
Time
Perception:

Three types of constancy are explained briefly
here:
 Size Constancy
 Shape Constancy
 Color Constancy
T
ypeofPerceptual
Constancy:

Size constancy is the tendency to perceive objects
in a consistent manner despite the changing sensations
that are received by our senses. visual constancy plays an
important role in helping us adapt to our environment
successfully.
Size constancy is the tendency to perceive the
size of an object as constant despite changes in its retinal
image.
Size
Constancy:

When we know that the object is a certain
shape ,we tend to perceive it as the same shape,
regardless of the viewing angle. We have learned
to make corrections in our perception dependent
on the angle from which we observe
Shape constancy means that your perception of
the shape of an object as viewed from different angles
does not change even though the image projected on
your retina does so.
Shape
Constancy:

Color Constancy:
Colors of objects tend to remain constant in
perception when we know their true color. Visual
objects also appear constant in their degree of
whiteness, grayness and blackness.

Something that looks or seems different from what
it is something that is false or not real but that seems to
be true or real.
Illusion
:

 Physical causes.
 Habit & Familiarity.
 Expectancy & Mental Set.
 Momentary State of Mind or Mood.
 Incomplete analysis of the collective impression.
 Apperception.
 Suggestion.
 Arrangement of stimuli.
Causesof
Illusion:

There are two type of illusion:
 Illusion Of motion.
 The Illusion Of forms.
T
ypeof
Illusion:

When a stationary stimulus is perceive as moving,
it is named as illusion of motion or movement.
IllusionOf
motion.

 The Illusion of Phi-phenomenon.
 The Illusion of Stroboscope.
 The Illusion of Gama phenomenon.
 The Illusion of Delta motion.
 The Illusion of Auto-Kinetic.
 The Illusion of Induced movement.
 The Illusion of negative after image of
movement.
T
ypesofIllusionof
motion:

Form perception is attained in relation to the
figure and ground according to the law of perception
Organization. As the figure is smaller then the ground
according to perceptual.
TheIllusionof
form:

The illusion of distance occurs when the parallel
lines seem to bend in different directions.
TheIllusionof
distance:

Psychologists have fail to understand this illusion. It
seem that the curving line behind the spiral have become the
cause of this illusion. The illusion is also known as the false
spiral, or by its original name, the twisted cord illusion.
Spiralcircle
illusion:

The parallel lines seem to bend to each other
instead of looking straight. The reason of this Illusion is
the smaller diagonal lines cutting the parallel line.
TheZollner
Illusion:

If two parallel line are dissected by another
straight line separately, a large straight line seem cutting
the parallel line instead of two partial line.
ThePoggindorf’
s
Illusion:

The Herring illusion can also be induced by a
background of optic flow. It is two horizontal line are
cure by the line of different direction, will not look
parallel. The distance between the two lines looks greater
where the lines assemble from different direction as is
found in fig
Herring’
s
Illusion:

TheIllusionofsize:
A near object is near usually perceived larger and
farther object is perceived smaller but in the moon
illusion, moon is perceived larger on horizon where the
earth and sky seem to meet.

Paranormal Phenomena
Extrasensory perception (ESP) refers to behaviors or
experiences that cannot be explained by information
received from the senses.
The term ESP is reserved for paranormal phenomena
that do not involve the senses.
The most frequently mentioned examples of ESP are
clairvoyance, telepathy, and precognition.

Clairvoyance is the claimed ability to “see” information from
objects or events without direct contact with the senses.
Telepathy is the claimed ability to perceive the thoughts or
emotions of others without the use of recognized senses.
Precognition is knowledge of a future event or circumstance
obtained by paranormal means.
Psychokinesis (once known as telekinesis) is the claimed power of
the mind to influence matter directly.
Because psychokinesis does not involve perception, some
researchers do not consider it an example of ESP.
The term parapsychology is often used to refer to “the study of
paranormal phenomena, which are considered to be well outside
the bounds of established science.”

The claims offered by supporters of ESP are sometimes presented
in ways that make designing a definitive test difficult, if not
impossible.
Most scientists agree that allegedly paranormal phenomena can be
explained without resort to non-normal evidence.
Many people have psychic experiences, or at least experiences
they interpret as such.
Psychologists suggest that paranormal experiences are an
inevitable consequence of the way we perceive and remember
information.
We can be fooled by our experiences in much the same way we are
fooled by the visual illusions described earlier.

Although the methods of studying paranormal phenomena have
improved, “the goal of a conclusively convincing demonstration or
a repeatable experiment has not been achieved.”
Should we therefore dismiss even the possibility of paranormal
phenomena?
Before we do, let’s consider an important history lesson: some
phenomena that in the past were considered to be paranormal,
impossible, or even fraudulent have since been verified to be real.

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