Ontario Normal School Manuals: Science of Education

by Ontario. Department of Education

Perception in Adult Life.—In our study of general method, sense perception was referred to as the most common mode of acquiring particular knowledge. A description of the development of this power to perceive objects through the senses should, therefore, prove of pedagogical value. But to understand how an individual acquires the ability to perceive objects, it is well to notice first what takes place in an ordinary adult act of perception, as for instance, when a man receives and interprets a colour stimulus and says that he perceives an orange. If we analyse the person's idea of an orange we find that it is made up of a number of different quality images—colour, taste, smell, touch, etc., organized into a single experience, or idea, and accepted as a mental representation of an object existing in space. When, therefore, the person referred to above says that he perceives an orange, what really happens is that he accepts the immediate colour and light sensation as a sign of the whole group of qualities which make up his notion of the external object, orange, the other qualities essential to the notion coming back from past experience to unite with the presented qualities. Owing to this fact, any ordinary act of perception is said to contain both presentative and representative elements. In the above example, for instance, the colour would be spoken of as a presentative element, because it is immediately presented to the mind in sensuous terms, or through the senses. Anything beyond this which goes to make up the individual's notion orange, and is revived from past experience, is spoken of as representative. For the same reason, the sensuous elements involved in an ordinary act of perception are often spoken of as immediate, and the others as mediate elements of knowledge.

Genesis of Perception.—To trace the development of this ability to mingle both presentative and representative elements of knowledge into a mental representation, or idea, of an external object, it is necessary to recall what has been noted regarding the relation of the nervous system to our conscious acts. When the young child first comes in contact with the world of strange objects with which he is surrounded, the impressions he receives therefrom will not at first have either the definite quality or the relation to an external thing which they later secure. As a being, however, whose first tendencies are those of movement, he grasps, bites, strokes, smells, etc., and thus goes out to meet whatever his surroundings thrust upon him. Gradually he finds himself expand to take in the existence of a something external to himself, and is finally able, as the necessary paths are laid down in his nervous system, to differentiate various quality images one from the other; as, touch, weight, temperature, light, sound, etc. This will at once involve, however, a corresponding relating, or synthetic, attitude of mind, in which different quality images, when experienced together as qualities of some vaguely felt thing, will be organized into a more or less definite knowledge, or idea, of that object, as illustrated in the figure below. As the child in time gains the ability to attend to the sensuous presentations which come to him, and to discriminate one sensation from another, he discovers in the vaguely known thing the images of touch, colour, taste, smell, etc., and finally associates them into the idea of a better known object, orange.

A. Unknown thing. B. Sensory stimuli. C. Sensory images. D. Idea of object.

Control of Sensory Image as Sign.—Since the various sense impressions are carried to the higher centres of the brain, they will not only be interpreted as sensory images and organized into a knowledge of external objects, but, owing to the retentive power of the nervous tissue, will also be subject to recall. As the child thus gains more and more the ability to organize and relate various sensory images into mental representations, or ideas, of external objects, he soon acquires such control over these organized groups, that when any particular sensation image out of a group is presented to the mind, it will be sufficient to call up the other qualities, or will be accepted as a sign of the presence of the object. When this stage of perceptual power is reached, an odour coming from the oven enables a person to perceive that a certain kind of meat is within, or a noise proceeding from the tower is sufficient to make known the presence of a bell. To possess the ability thus to refer one's sensations to an external object is to be able to perceive objects.

Fulness of Perception Based on Sensation.—From the foregoing account of the development of our perception of the external world, it becomes evident that our immediate knowledge, or idea, of an individual object will consist only of the images our senses have been able to discover either in that or other similar objects. To the person born without the sense of sight, for instance, the flower-bed can never be known as an object of tints and colours. To the person born deaf, the violin cannot really be known as a musical instrument. Moreover, only the person whose senses distinguish adequately variations in colour, sound, form, etc., is able to perceive fully the objects which present themselves to his senses. Even when the physical senses seem equally perfect, one man, through greater power of discrimination, perceives in the world of objects much that totally escapes the observation of another. The result is that few of us enter as fully as we might into the rich world of sights, sounds, etc., with which we are surrounded, because we fail to gain the abundant images that we might through certain of our senses.

FACTORS INVOLVED IN SENSATION

Passing to a consideration of the senses as organs through which the mind is made aware of the concrete world, it is to be noted that a number of factors precede the image, or mental interpretation, of the impression. When, for instance, the mind becomes cognizant of a musical note, an analysis of the whole process reveals the following factors:

1. The concrete object, as the vibrating string of a violin.

2. Sound waves proceeding from the vibrating object to the sense organ.