sensatio nand perceptionfinalfinal

SENSATION ANDPERCEPTION

SENSATION• It is the activity of the senses.

• A state of emotional excitement.

TWO FACTORS IN ORDER FOR SENSATION TO OCCUR:

1. There must be a stimulus.

2. There must be receptors that are sensitive to the stimulus.

KAGAN(1972)• Defines a STIMULUS as any form

of energy capable of exciting the nervous system like light waves, sound waves and chemical energy that causes the sensation of taste and smell. A RECEPTOR is a specialized nerve ending capable of responding to energy.

SENSES

The mechanisms which convert stimulus energy into neural energy

5 PRIMARY SENSES:

1. Vision2. Hearing3. Smell4. Taste5. Skin senses

In addition, we have

6. Kinaesthetic7. Sense of Equilibrium

VISION• Vision depends on the intersection

of EYES and BRAIN. The eyes sense object and then convey the information to the brain where visual perception takes place.

• The sense organ for vision is the EYE.

STRUCTURE OF THE EYE

COMPOSED OF 3 COATS:

1.SCLERA or the outer coat

• The protective outer layer of the eye, sometimes referred to as the “white of the eye”.

• it maintains the shape of the eye.

CORNEA• The front portion of the sclera.• It is transparent and allows

light to enter the eye.• It is a powerful refracting

surface, providing much of the eye's focusing power

2.CHOROID COAT or the middle coat

• The second layer of the eye and lies between the sclera and the retina. It contains the blood vessels that provide nourishment to the outer layers of the retina .

IRIS• It formed the colored portion of the

eye. It is a circular arrangement of muscles that contract and expand to change the size of the pupil depending upon the amount and intensity of illumination in a process of LIGHT OR DARK ADAPTATION.

• LIGHT ADAPTATION

- the process including contraction of the pupil by which the eye adapts to an increase in illumination.

DARK ADAPTATION

- The physical and chemical adjustments of the eye, including dilation of the pupil and increased activity of rods in the retina, that make vision possible in relative darkness.

PUPIL

•The apparently black circular opening in the centre of the iris of the eye, through which light passes to the retina.

LENS

• A transparent, biconvex body of the eye.

• The function of the lens is to refract and focus incoming light onto the retina for processing.

• The lens became thinner to bring far away objects into focus and thickens to focus on nearby objects. This process is called ACCOMODATION.

3.RETINA or the inner coat

• is the innermost layer in the eye

• It is composed of light sensitive cells known as rods and cones interconnected by a complex mesh of neurons that provide early stage visual processing.

ROD CELLS

• are primarily in the outer retina.

• do not discriminate colors.

• support vision in low light (“night vision”),

• are sensitive to object movement and provide

peripheral vision.

CONE CELLS

• are densely packed within the central visual field,

function best in bright light, process acute images and

discriminate colors.

MACULA• located in the back of the eye , in the center of

the retina.

FOVEA• most sensitive part of the retina which

contains only cones tightly packed together.• It is responsible for sharp vision which is

necessary for watching TV, driving and reading.

The inside of the eyeball is divided by the lens into two fluid-filled sections:

1. VITREOUS HUMOR• It is the larger section at the back of the eye.

It is filled with a colorless gelatinous mass.

2. AQUEOUS HUMOR• The smaller section in the front of the eye.• It contains a clear, water-like material.

CONJUNCTIVA

• is a mucous membrane that begins at the edge of the cornea and lines the inside surface of the eyelids and sclera, which serves to lubricate the eye.

DEFECTS OF VISION

Presbyopia

• a progressively diminishing ability of the eye to focus.

• noticeable from middle to old age.

• It is caused by loss of elasticity of the crystalline lens.

PRESBYOPIA

Hyperopia• Or farsightedness.• This is a defect of vision in which there is

difficulty with near vision but far objects can be seen easily.

• This occurs when the eyeball is too short or the refractive power of the lens is too weak.

• Hyperopia can be corrected by wearing glasses/contacts that contain convex lenses.

Hyperopia

Myopia

• This is also called nearsightedness.

• This is a defect of vision in which far objects appear blurred but near objects are seen clearly.

• Myopia can be corrected by wearing glasses/contacts with concave lenses these help to focus the image on the retina.

Myopia

Astigmatism• It is the result of an inability of the cornea to

properly focus an image onto the retina. The result is a blurred image.

• The main symptom of astigmatism is blurring. People can also experience headaches and eyestrain.

• Astigmatism can be treated by the use of cylindrical lenses. They can be in eyeglasses or contact lenses.

Astigmatism

Color Blindness

• Partially or totally unable to distinguish certain colors.

• It is caused by an inherited lack of one or another of the three types of cones.

• More men than women have defects of this kind.

Color Blindness

HEARING

• Most vital channel of interaction with the environment.

• The stimulus for hearing is in the form of sound waves.

• The human ear can register vibrations of air particles ranging in frequency from 16-20,000 per second.

STRUCTURE OF THE EAR

DIVIDED IN 3 PARTS

THE OUTER EAR

• This is the part of the ear that people can see.

• The main job of the outer ear is to collect sounds.

• The outer ear includes the pinna (also called auricle), the ear canal, and the very most superficial layer of the ear drum (also called the tympanic membrane).

PINNA• The visible part of the ear that resides

outside of the head.

• We often use the pinna, also called the auricle, for hanging earrings and resting eyeglasses, but the primary purpose of the pinna is to collect sound.

Auditory Canal

It provides a passageway for sound travelling from the pinna to the eardrum and it protects the ear from infection.

Eardrum• The eardrum plays a key role in hearing.

• Another word for eardrum is tympanic membrane.

• The eardrum is very thin and translucent.

• The eardrum vibrates when impacted by sound waves that have travelled through the auditory canal, and then transfers these vibrations to the middle ear.

THE MIDDLE EAR• Air-filled cavity behind the ear

drum (tympanic membrane), includes the three ear bones or ossicles: the malleus (or hammer), incus (or anvil), and stapes (or stirrup).

Malleus• The hammer-shaped bone that is the largest

and outermost of the three small bones (ossicles) in the middle ear.

Incus• the anvil-shaped small bone or ossicle in

the middle ear. It connects the malleus to the stapes.

Stapes• A small stirrup-shaped bone in the

middle ear, transmitting vibrations from the incus to the inner ear.

OVAL WINDOW• or vestibular window, is a

membrane-covered opening which leads from the middle ear to the vestibule of the inner ear.

ROUND WINDOW• a round opening between the

middle ear and the cochlea. It allows fluid in the cochlea to move.

THE INNER EAR

• Is rather complicated chambers and canals, called collectively the series of the labyrinth.

LABYRINTH• a system of passages comprising two

main functional parts:

1. COCHLEA

2. VESTICULAR CANAL

COCHLEA

• Which is a fluid filled bony structure shaped like a snail shell.

• It is dedicated to hearing.

VESTICULAR CANAL• The vestibular system of the inner ear is

responsible for the sensations of balance and motion.

• The vestibular system works with the visual system to keep objects in focus when the head is moving.

HEARING DEFECTS

Conductive Hearing Loss

• occurs when the transmission of sound through the outer and/or middle ear is interrupted. Common causes include wax buildup in the ear canal, a perforated eardrum, fluid in the middle ear, damaged ossicles.

Conductive Hearing Loss

Sensorineural Hearing Loss

• Occurs in the inner ear affecting the transmission of sound through the cochlea and/or the auditory nerve. Common causes include exposure to loud noise, trauma, the aging process, disease.

Sensorineural Hearing Loss

Mixed Hearing Loss

• Occurs in the outer and/or middle ear and inner ear. It is a combination of a conductive and sensorineural hearing loss. A mixed hearing loss can occur when a person has wax blockage in the ear canal and damage to the cochlea.

DECIBLE CHART

The Human Nose

Smell

At the very top to the nasal passages lies the Olfactory epithelium, the membrane that contains the receptors sensitive to smell. In man, there are about 5 square millimeters of olfactory epithelium in each nasal cavity.

The receptors for smell are called olfactory rods.

Smell• They are sensitive only to the gases and to

volatile substances that have been dissolved in the air.

• As we breathe normally, the air flows from the nostrils to the throat taking a direct route, but a certain amount rises gently to touch the olfactory epithelium.

Smell

• Sniffing helps in bringing stimuli to these sensitive areas. When the receptors are stimulated, they send neural impulses to the brain by way of the olfactory nerves

• The olfactory sense adapts to a constantly presented stimulus. The adaptation to a constant smell is quite complete after a few minutes. The olfactory sense also responds to a reduction of olfactory stimulation with an increased sensitivity to odors.

Human nose

The Human Tongue

Taste• What is generally called the

“taste” of food depends only in small part to the sensory receptors for taste. Much of the sensation depends on other factors.

Taste

• The receptor cells for taste are located in the taste buds on the upper surface of the tongue and to a lesser extent, on the surface of the pharynx and larynx.

• The receptor cells are specialized cells with hair like processes on their outer end.

Taste

• Food in solution spreads over the tongue, enters taste buds and sets off chemical changes that stimulate the receptors to set off neural impulses that are sent to the brain. The strength of the sensation depends upon both the quality of the substance and the location to which it is applied.

4 basic taste senses

Umami

• Now there's a new taste to learn and it's called umami (pronounced "oo-mommy"). Actually, while the term is new to us, it's not new to the Japanese, who have used the term to describe the "fifth taste" since the early 1900s.

• it's most often described as a "savory" or "meaty" taste.

Taste

• Tobacco smoke temporarily reduces the sensitivity of taste receptors.

• In people past middle age, the number of sensitive taste buds begins to decline.

The Skin Senses

• The skin has four separate senses: pain, pressure, coldness, and warmth.

• The nerve endings in the skin come in four general forms—some in little branches (called free nerve endings), some in globular bulbs, some in egg-shaped corpuscles, and some in the form of “baskets” surrounding root hairs.

• The stimulus for the pressure sense is slightly bending or slightly stretching of the surface of the skin.

The skin senses

• There are 135 pressure spots per square centimeter.

• The sense of the pain is not a simple one.• Sufficiently bright lights, loud noises, high or

low temperature, or great pressures all yield pain sensations.

• The receptors for pain are free nerve endings widely but unevenly distributed throughout the body.

Skin Receptors

The skin senses

• The sensation of cold appears to be simply the stimulation of cold receptors. The cold receptors are responsive to temperatures which are cooler than the body and the warmth receptors respond to stimuli that are warmer than the body.

• The simultaneous excitation of the warm and cool sense receptors yields a sensation of hotness called paradoxical heat.

Kinesthesis or the Sense of Bodily Movement

• They are in the muscles and are stimulated when the linings of the joints between our bones and are stimulated by movement of the joints.

• These receptors provide us with feedback informing about the success of movements which are in progress and the position and movement of our muscles and bones.

Equilibrium or the static sense

• These are in the semicircular canals and the vestibular canal. Both are located in the inner ear next to the cochlea.

• The three semicircular canals are located on different geometric plane, such that rotations of the head in any direction may be located. Each of these canals is filled with a fluid which resists movements by remaining stationary and causes hair cells attached to the moving walls to be stimulated.

Equilibrium or the static sense

• The vestibule lying between the semicircular canal and the cochlea operates on a similar principle. Resting upon the hair cells are otoliths. Vertical acceleration movement of the head changes the pressure of these otoliths upon the hair cells.

• The semicircular canals of the inner ear function in maintaining balance or equilibrium.

• The primary sensitivity of the vestibule is therefore to the position of the head with respect to gravity.

• Between them, the receptors of the vestibule make us constantly aware of the position of our head and any change in position.

• The messages operate by reflex actions to produce the muscular movements required to preserve our equilibrium.

The Organic Sense

• The organic sense gives the result of the sensitivity of the visceral and other internal organs of the body. Among the visceral are the stomach, intestines, sex structure, throat, heart, and lungs.

• When the sensory fibers of these organs are stimulated as a result of the activities of these organs, the nerve impulse are sent to the brain, thus giving rise to organic sensation.

The Organic Sense

• This organic sensation is related to biological drives and emotions.

• Our experience of the external world as well as what goes on inside us is dependent not only upon the activity of the sense receptors but also upon their connections with the central nervous system which makes perception possible.

PERCEPTION

Defenition of Perception• Perception as the process of knowing

objects and objective events by means of senses.

(Chaplin,1985)• The organization of sensory input into

meaningful experiences.

Perceptual Constancy

• Keeping the appearance of objects constant, even though their images in the retina are changing

Perceptual Constancy• Color Constancy

– An object in perceived as having roughly the same color regardless of the light source illuminating it.

Perceptual Constancy• Size Constancy

–Objects are perceived to have the same size no matter how far it is from us.

Point A

Point B

Perceptual Constancy

• Shape Constancy or Form Constancy– The tendency to see an object in standard

shape regardless of the viewing angle.

Perceptual Constancy• Location Constancy

–Despite the fact that a series of changing images strike the retina as we move, the position of fixed objects appear to remain constant.

Organization in Perception

• A. FIGURE and GROUND• When we perceive an object, usually one part tends to stand out

while the rest seems to remain in the background.

GROUND FIGURE

*The part which stands out is called the FIGURE and the rest of the stimulus pattern is called the GROUND

Organization in Perception

• B. GROUPING– The principles of group, first enunciated by

Gestalt psychologists, include similarity, proximity, closure and continuity.

Gestalt Principles of Grouping – Object are perceived to be together based on certain “Laws of perception.”

GESTALT PRICIPLES

• Reversible figures or Ambigous figures - visual illusions in which the figure and ground can be reversed.

REVERSIBLE FIGURES

GROUPING

• 1. The Principles of Similarity– Stimuli which are similar tend to be

perceived as a forming group.

GROUPING• 2. The Principle of Proximity

Objects near each other tend to be seen as a group or a unit.

GROUPING

3. The Principle of Closure

-When fragmentary stimuli form enough of a familiar figure, we tend to perceive the whole figure, ignoring the missing parts of parts

GROUPING

• 4. The Principle of Continuity– The stimuli which form a continuos pattern are

perceived as a whole, the pattern they make generally appears as a figure apart from the ground.

ATTENTION and PERCEPTION

• We select certain objects to perceive while ignoring others. This is called the perceptual focusing, attention.

(Hilgard, 1971)

• Attention is the direction of perception toward certain selected objects.

(Sartain, 1967)

ATTENTION and Perception

1. An intense stimulus is more likely to be noticed than one that is less intense.

ATTENTION AND PERCEPTION


2. A changing stimulus is more likely to be noticed than one that does not move.


3. A repeated stimulus is more likely to be noticed than one that is not repeated.


4. A contrasting stimulus is more likely to attract attention than one that is not contrasting.

Voluntary or Habitual• Attention may be voluntary or habitual.

• Voluntary attention is involved whenever one intentionally looks or listens.

• Habitual attention stems from motives. It is related to drives, interests, attitudes, prejudices and aspirations.

(Munn, 1969)

DEPTH PERCEPTION

:An understanding of how far an object is from us by converting two-dimensional information into three dimensions.

:It tells us which objects are closer or farther away from us.

Simple principles for depth perception (Edward, 1968)

1. Near things often appear in front of and hence cover up part of more distant objects. This the depth factor of relative position or superposition.


• 2. Objects appear smaller when farther away than when near. Linear perspective is one familiar sign of distance.


3. The lights and shadows upon parts of an object also give depth cues. They help define the contours of three-dimensional objects.


4. Distant objects appear hazy, while near objects are clear and distinct.


5. The relative movement of near and far objects when the observer is moving with respect to the objects.

Personal Factors in Perception

• The way we perceive objects is greatly determined by personal factors such as motives, emotions, attitudes and frame or reference.

• A change in our frame of reference will change the way we perceive an object.– A frame of reference as as system of related

categories in terms which judgements are made.

(Sartain)

Errors in Perception• Hallucinations- are false perceptions that occur

under abnormal conditions. • ILLUSION- Illusion is an error in perception

which depends on stimulus conditions and occurs in normal individuals.

ILLUSION BASED ON RELATIVE SIZE

ILLUSIONS BASED ON INTERSECTING LINES

PONZO ILLUSIONS

Müller-Lyer illusion

Extrasensory Perception

• It involves the belief that information maybe transmitted through the channel. This channel is called the sensory mechanisms.

Extrasensory Perception• Telephathy

– Motions of though transmission from one individual to another.

• Clairvoyance– Knowledge of happenings at another time

plane• Precognition

– Prediction of future events.

• Psychokinesis– The ability of inanimate objects to be moved by

mental power.

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