This article provides an overview on Perception.
Sensory Sign and Meaning:
We perceive objects and events with their qualities and relations. We do not see merely the field of view, but a field of objects. We see the position, size, shape, distance, and colours of objects, their motions and changes. Likewise, we smell, taste, hear and touch objects. We perceive not isolated stimuli but their patterns.
Perception is very much affected by learning. There is interdependence of perception and learning. We learn largely by observation. We observe largely by the use of what we have learned previously. Learning depends upon observation. Observation depends upon previous learning.
Sometimes we perceive merely a sign of some fact, but we perceive the fact. We interpret the meaning of the sensory sign, and perceive an object. We see that the ground is ‘wet’. Wetness cannot be seen but touched.
We see some cue or sign of wetness, and interpret its meaning in the light of the past tactual perception of wetness. The visual appearance is a sign of wetness. We saw wet ground in the past, touched it, and perceived its wetness.
Thus its visual appearance and tactual perception of its wetness were often associated in our past experience. Now we see its visual appearance, which is a sign of wetness, and perceive its wetness. We smell the colour of food and perceive the food with its smell, taste, temperature, and other qualities.
We interpret the meaning of the sensory sign, viz., odour, and perceive the object with all its qualities. We hear the rattling sound of a train, interpret the sensory sign in the light of our past experience, and perceive the train with all its parts and qualities.
A sign is a reduced cue. A person seen at a distance appears smaller than he really is, and his outlines appear vague. But still we understand the meanings of these reduced cues and recognize him. The connection between the sign and the meaning was learned by previous experience.
The meanings of objects are known from our useful activities. A book is what we read. A pen is what we write with. A chair is what we sit on. An orange is what we eat. Shoes are what we put on. Clothes are what we cover our bodies with. Thus the meanings of objects depend on doing.
The meanings of objects also depend upon their relations to other objects. This leg is a part of a chair. This chair belongs to a set of dining chairs. This medicine is necessary for digestion. The rainfall is good for crops. The flood is harmful for them. The meanings of objects are learned from experience.
Perception is the right interpretation of sensations. It is the right recognition of the meaning of sensory signs. Illusion is the wrong interpretation of the meaning of the sensory signs or sensations. It is a false perception.
There are some external stimuli in illusions, and they produce sensations. But they are wrongly interpreted by illusions. When we perceive a post as a post, we have perception. But when we perceive a post as a man, we have an illusion. When we mistake one thing for another, e.g., a rope for a snake, a bush for a bear, a patch of moonlight for a ghost, etc., we have illusions.
The Causes of Illusions:
(1) Some illusions are due to the external factors. A vertical line appears to be longer than a horizontal line of equal length because more muscles are exercised in vertical movements. When you look at a mirror, your reflection in it appears to be behind it.
When you cry aloud by the side of a lake, the echo seems to come from somebody across the lake. These illusions are due to physical causes. Cross fore finger and the middle finger and touch a pea with a crossed part; you seem to feel two peas. This is Aristotle’s illusion due to a physical cause.
Contrast is the cause of many illusions. A tall man appears to be taller by the side of a short man. A short man appears to be shorter by the side of a tall man. A Negro appears to be blacker by the side of a European.
Similarity is the cause of some illusions. We very often mistake one of the twin brothers for the other because of their close resemblance. We mistake a shell for silver, a zigzag rope for a serpent, the rays of the sun in a desert for water, because of similarity between them. We notice resemblance and ignore distinction between the objects, and consequently have illusions.
Movement is the cause of some illusions. A fire brand swung around produces the illusions of a circle. The gaps between the successive positions of the object are filled up by its after-images. When we travel in a fast moving train, the trees and houses nearby appear to move in the opposite direction, though they do not really move.
This illusion is due to the fast movement of the train. In a cinema show motionless pictures are exposed to our vision in rapid succession, which produce in us an illusion of movement. There is no real movement in the pictures. The illusion of movement is due to rapid succession of the motionless pictures.
Disorders in the sense-organs are the causes of some illusions. A white conchshell appears yellow to a person whose eyes are affected by jaundice. Sugar tastes insipid to a person who suffers from fever. These are the common peripherally excited illusions.
(2) Some illusions are due to the central interpretative factors. Habit and familiarity are the causes of some illusions. We apt to read the word mispirnt as misprint owing to habit. Proof reader’s illusions are the two habit An author is more subject to this kind of illusion than a professional proof-reader.
Expectation and set are the causes of some illusions. You eagerly expect a friend to join a dinner in your house. You are apt to mistake any man who comes for your friend. A mother on the ground floor with her mind pre-occupied with her sleeping baby on first floor, appears to hear him cry, when only a cat growls nearby.
Anxiety or fear is the cause of some illusions. A timid person in dread of burglars at night hears the sound of house-breaking when there is rustling of dry leaves trampled upon by a domestic dog. A loving mother hears her baby cry owing to anxiety. When a baby in the adjoining house cries.
Recency of a similar experience is the cause of some illusions. If a riot has recently broken out in a town, any disturbance will be mistaken for the outbreak of a riot. If an earthquake has recently happened in a region, any slight tremor due to the passing of a heavy-truck nearby will be mistaken for an earthquake. If a theft has recently been committed in a house, the nervous house-wife will easily be a victim of illusions.
Bias, prejudice, and substation are the causes of some illusions. Insane persons with their minds preoccupied with their suspicions are apt to mistake any sound for the enemy’s abusing them. These are the common centrally excited illusions.
(3) Imperfect isolation of the fact to be perceived is the causes of some illusions.—Many optical illusions described by Muller are of this type. Two lines of equal length are perceived to be unequal because they cannot be isolated from the irrelevant lines.
A figure is so drawn as to make it difficult to isolate the relevant fact from other irrelevant facts. The size-weight illusion is of this type. Take two round boxes, one several times the other in size, and load them so that both weigh the same. Then lift them in succession. You will feel the smaller box as the heavier one.
(1) Perception is the experience of objects and events in the environment. It involves attention which is selective. Perception is selective activity. Numerous stimuli assail our sense organs at a moment. We do not attend to all of them. We select certain stimuli which act upon a sense-organ and interpret the meaning of the sensations produced by them, and know an object in the environment.
(2) Perceptions combining or organizing activity. When we attend a dinner and eat food, we taste its tastes, smell its odours, touch its heat or cold and pressure, hear the sounds in the hall, see the items of food, etc., feel their weight, and combine the sensations into a unitary experience. Thus we perceive a dinner by organizing and integrating the different kinds of sensory experience.
(3) Perception is supplementing activity. We hear the whistle of a train and have a sensation of its sound. If suggests the colour, size, shape, movement, and Other qualities of the train. We supplement the ideas of these qualities which are not perceived at present, integrate them with the sensation of sound, and perceive the train as a whole.
Perception is sensations and ideas. Ideas are supplied by us through the force of association. Perception involves not only the activity of the receptors, of the sensory neurons, and of the sensory area, but also that of the association area of the cerebrum Perception depends upon the past experience.
(4) Perception consists in perceiving an object as a figure in a background.
(5) Perception involves affective processes. The gustatory perception of sweet taste is pleasant, and that of bitter taste is unpleasant. The auditory perception of music is pleasant, and that of noise is unpleasant. Sometimes the affective process accompanying perception depends upon past experience and social and cultural influence.
The gustatory perception of meat is pleasant to a non-vegetarian, but unpleasant to a vegetarian. The odour of leather is pleasant to a leather merchant, but unpleasant to others. The perception of a situation may involve aesthetic experience. We perceive a flower as beautiful, a scarecrow as ugly, and a post as indifferent.
The aesthetic experience depends upon affective process and past experience. A beautiful object is pleasant, an ugly object is unpleasant. A person who has a strong anti-European prejudice cannot easily distinguish between one European and another. But an unprejudiced person can distinguish between a white-skinned European and a dark-skinned European. Social and cultural influence is the cause of prejudice.