CHAPTER 4
SENSORY AND PERCEPTUAL MECHANISM
THE EXTERNAL SENSES
The intellect of man will be, according to Aristotle, a “tablet upon which
nothing is written,” if the external senses remain inactive or in a state of potency.
No knowledge is possible without external sensory experience. In the beginning of
knowledge, the senses have to be stimulated to function to provide the raw
materials, so to say, for the operations of man’s intellect. We have rejected the
theory of innate ideas of Descartes for what he states is not confirmed by our
immediate experiences. The importance of understanding the initial phase in
human cognition cannot be overstressed for the perfection of our intellect in one
way or another depends upon the certitude of knowledge we obtain through our
senses.
The Sense of Sight
This sense is very high in cognitive value because much of our knowledge
of objective sensible realities comes to us through the medium of this sense. The
organ used by the faculty is the eye. The human eye is a complicated organ with
many parts. The specific area used for seeing is the retina. In the retina are
structures called rods and cones which are regarded as the proper organ for seeing.
The optic nerve is the sensory nerve transmitting the stimulus or impression to the
center of the brain located in the occipital lobe at the back of the head. The proper
sensible for the sense of sight is colored surface. Color (refracted light) and light
are closely related. The light coming from the sun is white. It has no color but if it
would be allowed to pass through a prism, the edges of the latter deflect the ray
and separate it into different colors. Thus, we see red, blue, yellow, orange, green
and violet. White and black are frequently not considered specific colors. White is
the presence of all colors and black is the absence of all colors. It is said that of all
the external senses, the sense of sight is the noblest for it receives its proper
sensible in a more immaterial way than any of the other senses. When it acquires
the impression of color, its organ does not become colored.
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The Sense of Hearing
This sense is also high in cognitive value. The organ for the sense is the ear.
The ear is divided into the outer part which collects the sound waves, the middle
ear where the small bones, the incus, malleus, and stapes are found, and the inner
ear where the cochlea and the semicircular canals are found. Between the outer
and the middle ear is stretched the tympanum or ear drum which sends the
vibrations to the small bones which in turn send them to the cochlea. The specific
organ for the sense of hearing is the organ of Corti found in the cochlea. The
auditory nerve, also located in the cochlea, sends sonorous impressions to the
center of the brain, specifically the temporal lobe. Gases, liquids, and solids can
carry sound which is the proper sensible for the sense of hearing. Through the
sense of hearing, we can know the pitch, the timbre, and the intensity of sound. We
can likewise detect the difference between discordant and melodious sounds, and
articulate and inarticulate sounds.
The Sense of Touch
The sense is the most extensive of all the external senses because it
embraces several powers which are the sense of contact (passive touch), sense of
pressure (active touch), sense of temperature, sense of resistance to pressure
(kinesthetic sense), sense of pain and organic sense. Aristotle called the sense of
touch the somesthetic sense. The organ for this sense is the group of nerves and
corpuscles found under the skin. These nerves and corpuscles are instrumental in
the production of tactile nerves that carry the stimuli to the cerebral cortex where
the center for the sense of touch is located. The cerebral cortex is composed of
layers of gray matter covering the entire upper and lower surface of the cerebrum.
Through the sense of touch, we come to know texture, pressure, and temperature.
The Sense of Smell
The sense of smell uses as its organ the olfactory cells in the nasal
chambers located in the nose. These cells make it possible for us to acquire
impressions of odor from sensible realities. The olfactory nerve transmits the
stimulus to the center, said to be located at the base of the brain. Man’s sense of
smell cannot equal that of certain brutes, such as the hound for instance. As an
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instrument of knowledge, this sense ranks low in cognitive value because of the
following reasons:
(1)Sensations of smell and sensations of taste are often confused with each
other. When a person has a cold, he lacks the appetite to eat because
food seems to have an insipid flavor. This is because the person cannot
smell the food. After all, his nasal mucous membrane is congested. It is
a common experience that the mere odor of food whets the appetite and
starts the craving for the food.
(2)When the stimulus is presented continuously for a certain period, the
faculty has its sensibility dulled and recovery of the power of sensibility
is very slow. If we hold a close to our nose a perfumed handkerchief for
a long time, we will observe that at the beginning, the sensation is very
pleasant. We smell the fragrance of the object. But as minutes pass the
initial reaction disappears and the stimulus ceases to be as effective as it
was at the beginning. If the object is removed and a new odor is
substituted, we may not be able to detect the latter because of the slow
recuperative power of the faculty.
The Sense of Taste
The organ for this sense is the tongue. On the surface of the tongue are the
taste buds which are responsible for our acquisition of gustatory impressions. The
gustatory nerve carries the stimulus to the base of the brain. The proper sensible
for this faculty is flavor, but to be able to excite the organ of taste, the substance
placed in the mouth must be sapid or soluble. Without solubility, no substances
can be tasted. The sense of taste is low in cognitive value because just like the
sense of smell, its sensibility can be easily dulled and it does not recover the power
immediately. If we put a piece of ice on the tongue and retain it, for, say, three or
four minutes, the tongue feels numb and even though something bitter or pungent
would be placed on it, we would not be able to sense it. Mothers giving their
children purgative frequently resort to this method to conceal the unpleasant flavor
of the medicine. Aside from the fact that the recuperative power is low, sensations
of taste are oftentimes confused with sensations of smell. However, it is already
well-developed at birth for a newly-born child can suck and, as Kelly says, “can
distinguish between sweet and sour or bitter substances.”
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Reliability of the Senses
Strictly speaking, the external senses cannot deceive us regarding their
proper senses; otherwise, they would act contrary to their nature. But we may be
puzzled by the errors we commit upon seeing objects and not being accurate in our
observation of them. We may start doubting the validity of impressions we receive
through sensory media. To uphold the truth of the statement that our external
senses cannot deceive us regarding their proper objects; we have to explain briefly
what error is and how it can intrude in our sensory experiences. Error is properly
found in a judgment, not in sense cognition as such. Therefore, it has to be
ascribed to the intellect concluding insufficient or unsatisfactory evidence. In a
way, it can be said that indirectly, the senses contribute to faulty reasoning because
of the inadequacy of sensory data. This inadequacy is caused probably, by
defective sense organs, by lack of clearness in the presentation of the object, by a
too fertile imagination or by inability to attend to the matter being observed or
faulty interpretation leading to inaccuracies in sensing proper sensible such as
mistaking the back-firing of a car for a pistol shot or confounding the varying hues
of colors with one another.
SENSATION AND PERCEPTION
The Difference between the Sensation and Perception
Through the external senses, we experience sensations. Sensation is an
animal function because it is sensitive but it should not be confused with
perception. Both of them are aspects of sense cognition or the process of acquiring
sense knowledge, but each has a different nature. Sensation has been defined often
as the consciousness of a being about an external, exciting force. This definition, it
is admitted, may lack clarity since it may convey, too, the idea of perception. We
may consider sensation as awareness of an object preceding the act of perception.
It is a vital operation that results in knowledge initiated by an object stimulating
the sensory organs. “it is the awareness of singular, concrete, material objects in a
material way.” It is the awareness of something singular because the senses can
know only this tree, or this man, or this animal. It is concerned with knowledge of
material objects materially because, in the act of sensation, the soul depends
extrinsically on matter. The object of knowledge is material and it is received with
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the conditions of matter. In sensation, there is a transit from potency to act affected
by nerve excitation caused by an extra-mental sensible being. The likeness
acquired by the knower in sensation is an impressed species, an intentional form.
Although in itself it is immaterial, it is received with the conditions of matter, for it
is a form found in an individual, concrete reality. Beings capable of experiencing
sensations are called sensible, sensitive, or sentient.
It is necessary to distinguish sensation from perception to avoid attributing
to the external senses certain activities which do not properly belong to them. If
the sensation is awareness of a sensible object stimulating the sense organs,
perception is cognizing the object which excites the same organs. “Sensation has
reference solely to the stimulus.” Here are some examples. We enter a room and
see a red notebook on the table. If we say, “I see something red,” we refer to our
sensation. But when say, “I see a red notebook,” we refer to our perception. We go
to a garden full of flowers in bloom. We say, “I smell something fragrant.” This is
a sensation. When we remark that we smell rose, sampaguita, etc., then, that is
perception. “Perception always involves past sensations of the same and different
kinds and combine them in the recognition of the object which caused them.”
In man, it is oftentimes difficult to set a demarcation line between what is
sensuously perceived and what is understood by the intellect. In the foregoing
examples, the designation of sensed objects as a notebook, a flower, or any
specific individual reality, implies knowledge of nature and essences.
If sensation is the reaction of conscious beings to a stimulus, perception is
the act of integrating the sensation or the act of discriminating among the senses
acquired or obtained by the external senses. Each of these faculties has its proper
sensible and each cannot know the proper sensible of the others. Sight receives
color; it cannot receive sound. These proper senses received by the external senses
exist in the faculties as isolated impression units. They have to be integrated or
unified into wholes if we are to know what the objective reality is. This unification
of impressions is done not by any of the external senses but by an internal sense
which is the common sense, so called because according to St. Thomas, “it is the
unit principle of all acts of the external sensations.” It acts as a liaison between the
external and internal senses.
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Characteristic of Sensation
Sensation has certain properties. They are quality, intensity, extensity, and
duration.
(1)Quality is the specific element in an act of sensation that enables the subject
or known to distinguish sensations experienced through different senses or
to differentiate sensations produced by the same senses. Sensations of color
are different from sensations of temperature. Sensations of melodious
sounds are different from those of a discordant nature. The sensations
resulting from the apprehension of green and red objects are not the same as
those produced by the apprehension of blue and white.
(2)Intensity refers to the vividness of sensation, whether it produces a strong
or a weak impression in consciousness. A very loud voice tends to produce
a strong impression in consciousness, whereas a weak voice results in just a
faint impression. The degree of intensity is determined in part by the kind
of attention accorded to the stimulus.
(3)Extensity means awareness of the bodily area being subjected to the action
of the stimulus or awareness of the length and breadth of the object exciting
the sense organs. The consciousness of wading in the flood differs from that
of swimming in the pool or the river. In the first example, only the feet
touch the water but in the second example, the whole body comes in
contact with water.
(4)The last characteristic is duration which indicates the length of time the
sensation continues or persists. This depends on the continuance of the
stimulus and the power of the faculty. The senses of smell and taste are
easily dulled by continued stimulation and so, for them, the duration is
shorter than for the other senses.
The Act of Sensation
In the production of sensation, there are three levels, viz., the physical, the
physiological or neurological, and the psychological or psychical. On the physical
level, an external object or stimulus acts on an end organ, e.g., the eye or the ear.
On the neurological or physiological level, the organ stimulated reacts and the
impulse or impression is transmitted by the sensory nerves. On the psychological
or psychical level, there is consciousness and reaction of the sentient being to the
stimulus. Thus, if a colored object is presented to the sense of sight (physical), the
optic nerve is excited and carries the impressions to the cerebrum (neurological).
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The visual area receives the impression and the being sees something colored
(psychological). It must be remembered, though, that it is the subject or the
knower that sees and not the eyes that see. The ayes are merely the material organs
with which the subject sees.
Sensation, however, is not enough to give an adequate knowledge of an
objective reality present. Perception is needed, because as Brennan says,
“sensations in their simple elemental form, as operations of the external sense, do
not exist except as part of a more whole-making process which we term
perception. We see something colored or smell something sweet, or something
feels soft to the touch, but what that something is would remain unknown if
perception were absent.
PERCEPTION
Perception – is the interpretation or the giving of meaning to a stimulus received
by the sense organs.
Two Requisites of Normal Perception
1. The nervous system and the sense organs must be in excellent condition.
2. The stimulus must be above the threshold, either absolute or difference
threshold.
Two Theories of Development Of Perception
1. Nativist’s Theory – development is inborn and inherent.
2. Empiricist’s Theory – perception is developmental and is learned.
Factors That Influence Perception
1. INTENSITY – the more intense the stimulus, the more likely it is to be
attended to and perceived, like the use of “neon lights” in advertising.
2. REPETITION – repeating the stimulus with some variations. Used by
advertisers very effectively in stressing a point to the consumers.
3. CONTRAST – an intensified difference from the immediate surroundings,
like the wearing of uniforms and colorful attires.
4. CONTINUITY – stimuli that maintain a steady flow of regularity.
5. CLOSURE – the possibility for an individual to “complete” or make
“incomplete” the stimulus presented to him.
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6. MOVEMENT – moving stimuli are more likely to attract attention than
stationary ones.
7. CHANGE – change in the characteristics of the stimulus as a result of
lighting and movement may aid in the easier perception of an object, like
the illuminator in billboards.
8. PERCEPTUAL GROUPING AND PATTERNING – tendency to look for
some systematic organization or ordered relationship among the elements.
9. FIGURE AND GROUND – some objects stand out clearly to one’s
awareness while others reside in the background.
Types Of Perception
1. PERCEPTION OF OBJECTS – involves the interaction of many senses,
but vision seems to be the preferred sense. Object perception is
developmental and is relatively stable or constant.
2. PERCEPTION OF DEPTH – because our retina can register only two
dimensions; “length” and “width,” different cues are used to infer depth
under different circumstances.
3. PERCEPTION OF MOVEMENT – the ability to perceive movement and
to discriminate apparent motion from real motion can determine our
adjustment patterns to specific situations.
4. PERCEPTION OF TIME – the perception of time is related to some factors
among which are certain variables within our experience. It is also
influenced by conditioning.
Extrasensory Perception (Esp)
Extrasensory Perception – perception is involving a source other than the
senses; or simply perception without sensation, the “sixth sense.”
Types of ESP or “psychic phenomena”
1. Telepathy – is the transfer of thoughts from one person to another
without the usual aid of the sense organs.
2. Precognition – the ability to anticipate future events before they happen.
3. Clairvoyance – the ability to “see” without the use of the eyes and thus
reveal information that otherwise could have been received by normal
sense organ stimulation. Mentally seeing things hidden from sight.
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4. Psychokinesis – the capacity to move objects by using only thought
processes or by mental suggestion, like Uri Geller’s bending of spoons.
INTELLIGENCE
Intelligence – is a composite of general and specific abilities. It characterizes an
individual’s level of neurological functioning which is manifested in how he copes
with the challenges of everyday living.
Interaction Of Heredity And Environment
Heredity and environment are complimentary contributions to an individual’s
intellectual maturity. Ideally, heredity provides enough potential, and the
environment provides challenging stimuli for learning and development.
Personality and Intelligence
The personality traits that facilitate intellectual development are curiosity, verbal
expressiveness, analytical thinking, optimism, and perseverance. The traits that
construct intellectual development are conformity, passivity, fear of the unknown,
emotional instability, and lack of perseverance.
Assesment of Inteligence
Intelligence tests are used to assess an individual’s performance on certain skills
considered necessary for effective intellectual functioning.
Types of Intelligence Test
1. Stanford – Binet Intelligence Scale (SBIS) – an individual test used
primarily with children. It consists of a series of subjects arranged
according to age levels.
2. Wechsler Adult Intelligence Scale (WAIS) – an individual test requiring
many props and expert testers. It consists of six verbal subtests and five
performance subtests.
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Determinants Of Intelligence
1. Hereditary – though genetic factors influence intelligence there is no
evidence to show precisely to what extent heredity influences mental
ability. Heredity is not exactly the real gauge of intelligence.
2. Social (Culture) -environmental conditions have been formed to relate to
individuals and group scores on mental ability.
3. Educational – the quantity and quality of the educational stimulation
influence the degree to which the child’s genetic potentials are tapped and
developed. Good education stimulates intelligence
4. Maturation (age) – intelligence develops with age until adolescence and
possibly a little later. Remain constant up to middle age after which it
declines.
5. Sex – men appear to do better in space relations, such as map reading and
calculating distance whereas women do better in verbal or language ability.
GENIUSES AND DEFECTIVES
Men tend to have extreme levels of IQs either higher or lower compared to
women since more male scientists and political figures have been recorded in
history. The reason lies in the role expectations assigned to men and women. Men,
considered the head of the family, must do a lot of thinking to favorably compete
in the outside world while women are biologically meant for motherhood and
childbearing and so must render service at home.
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Name: _____________________________ Rating: _______________
Course/Yr/Sec_______________________ Date: ________________
Quiz No. 4
I. IDENTIFY THE FOLLOWING:
1. The interpretation or the giving of meaning to a stimulus received by the
sense organs.
____________________________________________________________
2. An individual test used primarily with children. It consists of a series of
subjects arranged according to aged levels.
____________________________________________________________
3. An individual test requiring many props and expert testers. It consists of six
verbal subtest and five performance subtests.
____________________________________________________________
4. The capacity to move objects by using only thought processes or by mental
suggestion, like Uri Geller’s bending of spoons.
____________________________________________________________
5. Used to assess an individual’s performance on certain skills considered
necessary for effective intellectual functioning.
____________________________________________________________
6. The ability to “see” without the use of the eyes and thus reveal information
that otherwise could have been received by normal sense organ stimulation.
Mentally seeing things hidden from sight.
____________________________________________________________
7. Complimentary contributions to an individual’s intellectual maturity.
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8. Ability to anticipate future events before they happen.
____________________________________________________________
9. Development is inborn and inherent.
____________________________________________________________
10.Ability to transfer thoughts from one person to another without the usual
aid of the sense organs.
____________________________________________________________
11.Ability to perceive movement and to discriminate apparent motion from
real motion can determine our adjustment patterns to specific situations.
____________________________________________________________
12.Composite of general ad specific abilities.
____________________________________________________________
13. Involves the interaction of many senses, but vision seems to be the
preferred sense.
____________________________________________________________
14.Perception is developmental and is learned.
____________________________________________________________
15. Stimuli that maintains a steady flow of regularity.
II. ENUMERATE THE FOLLOWING:
A. Types of Intelligence Test
1.
2.
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B. Types Of Perception
3
4.
5.
6.
C. Sensory System
7.
11.
12.
13.
14.
C. External Senses
15.
16.
17.
18.
19.
D. Characteristic of Sensation
20.
21.
22.
23.
E. Two Requisites of Normal Perception
24.
25.
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