What is Sensation, Attention and Perception ?

What is Sensation, Attention and Perception ?

Humans gather information about their surrounding external world through the sensory organs. There are various stimuli in the external environment but human being select some liked stimuli and gives complete mental concentration towards it. Human being with their former experiences and education can have in depth understanding of the stimulus and then behave accordingly. In Psychology, this process of human behaviour is known in a particular sequence as sensation, attention and perception.

SENSATION

"An experience regarding a Stimulus through the Sensory organs". Any type of external stimuli affects sense organs and afferent nerves near the sense organs are excited and this excitation reaches a specific area of the brain.

Sensation means "An experience arising out of this is called Sensation" Thus sensation is a change in consciousness that arise out of excitation which reaches the sensory centers in the brain.

Physiologists and Psychologists have divided sensation into three classes and they are as follow:

1] External receptors:- The external physical environment is constantly humming with changes in stumulus like light, sound, heat, cold, touch, pressure, chemical air, chemical liquid etc. which affect our different sense organs and hence we can experience different types of sensations.

2] Body receptors:- Just like the external environmental components, the human bodys internal physiological system is responsible for different sensations. e.g., excitation of the rods and cones for visual sensation excitation of microscopic hair calls for auditory sensation etc.

3] Internal receptors:- Internal sensations arise because of changes and movements in the organs within the body and in the internal physiological system, e.g., hunger(in stomach), thirst because of dryness in throat, suffocation, change in blood circulation etc.

It is observed that different animal species differ in their capacity for different kinds of sensitivity. In the same way, we can observe the differences in sensitivity between different human beings. By special training and experience human beings can not only develop but also increase their sensitivity.

Type of Sensations

There are five types of sensations based on five sensory organs. They are as follows:

1} Visual Sensation

2} Auditory Sensation

3} Olfactory Sensation

4} Gustatory Sensation (Taste)

5} Touch Sensation (Skin)

1] Visual Sensation:- Out of all senses vision has the most important role in human life. Composition of the eye, its internal organs, the nerves that go towards the brain and the brain are all included in the process of visual sensation. To experience visual sensation presense of light is inevitable and is must. the external eye can be seen only when we stand in front of the mirror or when we look at someone else's eye. The white part of the eye is a tough outer layer called Sclera. It is made ot white fibres, not transparent and hence can protect the inside of the eye. The black  part of the eye called pupil is transparent and it is through it the light enters the eye and reaches the retina. The grey or blue area which can be seen in the Sclera is called Iris and also the ciliary muscles of the eye. It is because of it that the colour of the eyes can be seen. These ciliary muscles are not interconnected and they do not touch each other. The space between them is called the pupil. The pupil is not any organ but 1/8 inch hole located in the center of the Iris.the physiological and internal structure of the eye. Rays of light emanating from external object enter the eye through the pupil then its reaches the retina by passing through the transparent vitreous humor in the space within the eye which is the area for visual sensation and so because of it one can experience visual sensation. How much intensity of light will reach the retina will depend on the contraction and expansion of the ciliary muscles. They are very sensitive to the intensity of light rays. When light increases the ciliary muscles get expanded and the size of the pupil becomes small and if light decrease, than the size of the pupil increases. To experience the sensation of near and far objects, retina and ciliary muscles play an important role in visual sensation.

2] Auditory Sensation:- To be connected with the outer world, an individual should possess adequate auditory sense organ. To understand the direction of sound, its distance and to be able to differentiate between sound waves it is necessary to possess a sharp and active auditory sensation.

Normally a man's ear is capable to hear and distinguish sound waves from 20 to 20,000 Hz i.c CPS (cycle per second). Sound waves which are more than 20,000 or less than 20 cannot be heard by the human ear.

To understand auditory sensation in details it is divided into three classes:

a) Outer ear:- This includes the ear lobe, auditory canal and the ear drum.

b) Middle ear:- The Middle ear is made up of three interconnected bones like hammer, anvil and stirrup. It has also got the Eustachian tube, its second part opens in the throat.

c) Inner ear:- It is devided into three main parts: 

(1) Middle ear

(2) Cochlea

(3) Semicircular canals

Sound waves from the environment enter through the outer ear into the external auditory canal and in middle ear stimulates the ear drum. Eardrum vibrates with the sound waves and activates the three bones. Vibration of these three bones transmits the concentrated energy to chochlea and sets the fluid inside the cochlea into a wave motion. The fluid waves causes the basilar membrane to move bending its tiny hair cells, the auditory receptors. Neural impulses through the auditory nerve reach the auditory area in the brain and so there is sensation of hearing.

3] Olfactory Sensation:- Physical stimuli for smell are molecules of chemical compounds dissolved in air and this smell reaches the olfactory receptors in the nose. Smell receptors are olfactory cilia, hair like structures located in upper portion in a narrow canal of the nasal passage. Olfactory receptors through olfactory nerves are connected with the base of the brain. Each such cell type responds to different kinds of smell and it can be said that olfactory sensation takes place.

There are individual differences in olfactory sensitivity. A strong smell emanting from chemical compounds may arise a sensation in one individual whereas the some smell may not arise any sensation in another individual. Sense of smell shows sensory adaptation because when there is continuous experience of a particular smell, the intensity of this sensory experience decreases and the person gets habituated to it.

4] Gustatory Sensation:- physical stimuli of Taste are chemical substances from the external environment which create taste sensation through the tongue. Tongue is involved not only in taste sensation but it is also important in development of speech. It is a muscular organ and attached to the end of the jaw. Taste buds are spread over the entire surface of the tongue gave and they arouse the experience of taste. They are also called taste receptors.

At its base every taste bud is connected with the ends of taste receptors. A substance, which can melt in saliva if put over the tongue, it stimulates taste buds. Its neural stimulation reaches the brain and arouses the experience of taste. There are different areas on the tongue for experiencing different kinds of tastes. Each basic taste has a specific kind of taste buds.Which are divided into four types. Sweet taste buds are on the tip of the tongue, Salty taste buds are on both side of the tongue just behind the tip further ahead on both sides is sour and buds for bitter taste are located on the back part of the tongue. As per Ayurvedic view, there are four basic tastes i.e. sweet, salty, sour and bitter but in addition to it there is spicy and astrigent which makes it total six types of tastes.

5] Touch Sensation:- We can experience touch sensation because of the layer of skin on the entire human body and they are of four types. They include warmth, cold, touch, pressure, pain etc. As per different studies and experiments performed in psychological laboratories it is found that touch sensation is experienced due to excitation of sensory receptors spread all over the skin of the human body. we can experience touch sensation on the face when the skin of the face is stimulated by touch and it sends message to the brain in the same way sensations from shoulder to waist are send through excited skin receotors via spinal cord to the lateral part of the brain which is the center point of touch sensation and hence we can experience touch sensation. Most of our sensory experiences from the skin are of mixed type because skin stimulus activates more than one type of receptors. e.g., we can experience the sensation of coolness and touch both simultaneously when a drop of rain water falls on the body.