We used to take our ability to see, hear, touch, taste and smell for granted. It was commonly thought that our senses were fully developed soon after we were born. However, in recent years, we have come to realize that development of our ability to use our senses is far more involved than we had previously thought.
First of all, we now understand that our ability to use our senses develops during the first six years of life. During the earliest years, the nervous system is still forming. The extent to which the nervous system develops depends upon proper nutrition and adequate stimulation. Recent research on monkeys provides convincing evidence that inadequate stimulation of touch and other senses leads to a much lesser development of neural connections and branching. It has been found that once this critical period for biological development has passed, that it cannot be made up later.
Nerve endings, connections, and branching are not the only aspects of the nervous system developing during the first six years. Optometrists claim that the eye itself continues to develop during this period. Therefore, optometrists like to examine a child's ability to see at three years of age to determine whether the eye is developing properly. If the eye is developing inadequately, optometrists prescribe visual exercises for the child to help the eye in its development. It seems that the way the eye is used influences how it develops. Therefore, we must be careful that the child has the opportunity to engage in activities that will give the eye full chance to develop.
Certainly we want to provide the necessary conditions for full biological development of the nervous system. This means the child needs proper stimulation and opportunity for activity. Scientists have shown that development does not take place through passive inactivity. This was dramatically demonstrated by an experiment involving mice. During the critical period of early development, mice were placed in a dark box so they could not see. When the mice grew up and were allowed out into the light, they were blind and were never able to see. The experiment provided one more piece of evidence to support scientists' growing conviction that early experience is important in the development of the senses. This led scientists to wonder what kind of experience is necessary for the development of the nervous system. One simple experiment tested for the difference between active and passive experience. A new group of mice were raised in a dark box where they could not see. The conditions were similar to the previous experiment. However, this time, the mice were allowed out into the light for a period of time every day.
The mice were divided into two groups. The first group of mice could wander around freely exploring their environment. Their only limitation was that they were harnessed to a cart carrying the second group of mice. This second group of mice, while pulled in the cart, got a chance to be visually exposed to the same environment, for the same length of time, as the first group. However, this second group viewed the scene passively. So, how did the vision in the two groups of mice develop? It was found that the mice from the active group developed an ability to see and use their eyes, while the passive group of mice never did develop vision. The experiment showed that interaction with the environment is critical to the development of the senses.
The idea that activity is a necessary condition for development is further illustrated by the case of a boy born to two deaf parents. Doctors determined that the boy was born with normal hearing. He could hear and respond to sound. Therefore, the parents wanted him to learn to speak an oral language. They spoke in sign language themselves. So, in order to have the child exposed to oral language, they had him watch television everyday. However, he did not develop an ability to either understand or speak English, although he did develop an ability to communicate with sign language. Exposure to language was not enough to promote development of the ability to speak. Since the child lacked the opportunity to interact with the sounds of language, development did not occur.
The importance of active experience has been illustrated over and over again in so many different ways that we now realize that experience not only fosters biological development, it is necessary for learning how to interpret the information the biological mechanisms give us. For full perceptual development, the sensory structures must be developed to their full potential, and we must learn to interpret and understand the signals that they send.
Perceptual development depends on learning as well as on physical development. The importance of the role learning plays in perception was clearly illustrated when doctors developed a medical procedure which allowed some people, blind since birth, to gain vision. These people had learned to function adequately without the sense of sight. When, as adults, these people underwent corrective surgery, science gained dramatic new evidence showing the relationship between perception and learning. After the first patient's operation, doctors were quite anxious to see how the patient would respond after bandages were removed from her eyes. They asked if she could see. To their dismay, she replied that she couldn't. However, she claimed to be experiencing a strange sensation that she had never experienced before. So, the doctors wondered if the sensation was coming from her eyes. She answered that it didn't seem so. After some thought, the doctors suggested that she close her eyes and then open them. To her surprise, the sensation went away when she closed her eyes and then returned when she opened them. She hadn't realized that the new sensation was coming from her eyes until she shut and then reopend her eyes. Sensation by itself was not enough. She had to learn to interpret it.
Scientists have been studying the relationship between sensation and perception for a number of years. After the television camera was invented, scientists wondered if there might not be a way to use the camera to help blind people get a sense of what was in front of them. A team developed a tactile device that translated the signal from a television camera into a grid of electrical stimulators. Normally, a television picture is made up of dots of light which light up the television screen. However, in this case, each dot consisted of an electrical signal sent to an electrical prong, each of which could stimulate one tiny spot on a human's skin. Therefore, a picture from the television camera would be translated to a pattern of electrically stimulated points on the skin. This device was then strapped onto a scientist's back to see if he could figure out the picture the camera was sending by feeling a pattern of sensation on his back. The scientist's experience was revealing. He could not depict any pattern out of the strange tickling sensations on his back. However, he soon realized that a vague image was forming in his "mind's eye." With feedback and experience, the image got more distinct. Here was a clear example illustrating the difference between sensation and perception. The scientist had felt sensation on his back, and separately perceived an image in his mind. The perceived image improved with feedback which showed the part that learning contributes to perception.
The role of learning in perception becomes even more clear when we look at the experiences of the blind adults who gain vision for the first time through surgery. After sight has been gained, it has been found that the previously blind person may walk into walls, stumble over furniture, and trip down stairs. Although their eyes now function normally, they have not yet learned to interpret what they see. They have not yet learned to distinguish line, shape, edge, color, depth, and contrast. Such is also the case for very young children. This can be observed by watching children when they take an imbedded figure test, do a puzzle, work with a shape sorting box, or engage in a similar activity. For us as adults, it may seem puzzling to see a young 18-month-old child gleefully scampering after a texture ball and then apparently loose track of it when it is still right in front of the child. As long as the ball is placed on a rug free of design and color patterns, the child will snatch up the multicolored texture ball. However, if the texture ball is tossed on a pile of toys, the toddler may not be able to find it. He will not be able to distinguish it from the multiplicity of lines, shapes, and colors mixed together in the pile of toys. Because young children are still learning to intrepret visual cues, they will try to place two puzzle pieces together which the adult sees obviously won't fit, the two-year-old will try to fit round pegs into holes which are too small, or rectangular blocks into triangular holes.
The above are but a few illustrations. There are many examples we can observe if we stop to watch children. In observing children, it can be noticed that at certain ages, children around the world engage in similar activities. Children appear to have a natural inner interest in exploring their world through their senses and refining their ability to use their senses. Adults can help by providing material which suits the child's interest and activity. It's possible to see this principle at work when a teacher, noticing a three-year-old sitting on a lawn, feeling the grass with his or her hand, later provides the child some interesting textures to feel.
In this way, the adult ensures that the child has opportunity to engage in activities which are necessary for development. These activities are not forced upon the child. Instead, they are made available to the child. It is important to realize that as humans take responsibility for creating an artificial human-made environment, humans must make the provisions in that environment necessary for life and its development. Children used to be able to run freely in the country and climb trees, grab limbs, feel bark, watch caterpillars, roll down hills, chase balls, etc. Today, it is harder for children to get those kinds of natural experiences living in cities. It is easy for a child to end up seated in front of a television, at a fixed focal distance, watching a screen with consistent contrast, and images fixed in only two dimensions. This represents a passive type of activity which does not promote development. So, in having the child placed in this artificial and limited environment, the adult needs to be consciously aware of the requirements for development and purposely make provision to see that they are met.
Today, we realize that perceptual development is not automatic, and we are further beginning to understand that development of the senses is the foundation of intelligence. We often hear that schools should teach the basics. Most people think the basics are reading, writing, and arithmetic. However, today, more and more, we hear of teachers having difficulty teaching children to read. Children may experience reversal problems and get mixed up between a "b" and a "d" or even a "p" and a "b." The children claim the letters look the same. So, is reading really the first basic? Or, is the ability to distinguish line, shape, and position in space more basic? Obviously, our ability to receive information through our senses and interpret it will have great influence on our intelligence and our ability to read, write, or do anything. Without our senses, our mind would not have any way to receive information at all. Our potential for development is tied to our perceptual development, and our ability to use our senses is related to our early experience.
Lack of proper early experience limits future possibilities. We can see this today in the number of people in the United States who claim to be tone deaf. As adults, these people find that they can't carry a tune or pick out a melody on an instrument. Their ability to enjoy and participate in music is greatly limited and hindered by their lack of early experience which could have helped them develop the ability to discriminate pitch. Theirs is not a physical or genetic problem. Rather, it is educational. There are other cultures that do not have such a high percentage of tone deaf citizens. In fact, in Hungary, where music is very much a part of the culture, tone deafness is almost unheard of. The result is that the people enjoy music. Factory workers form choirs just as our workers often form bowling leagues. This is but one example. However, the lesson is clear. We must not assume that perceptual development is automatic or that it is unimportant. We must see that children get the experiences they need in order to develop properly and fully.
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