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The Principles of Growth and Development: Further exploration into the diversity of growth and development

Although I have written about the principles of development in my previous article, I would like to explore further, the variances in the speed of growth and development, which I have called the second principle.

When age, from the point of birth, is portrayed in terms of figures of height and weight, the graph looks like an extended letter "s". The famous Scamon's growth curve portrays this same extended "s" shape and is said to be the general curve for growth. However, the reader is probably well aware that the growth curve of the lymph glands, the brain and reproductive organs can follow an entirely different pattern.

From the moment of birth, the weight of the brain grows rapidly until the age of five, when the brain at this age is already about 80% of the weight of most adults. This is due to the fact that the function of the cerebrum is indispensable for human existence.

At birth, the weight of the cerebrum is about 10% of the total weight (approximately 300 grams), but by one years old, the weight increases threefold from the time of birth. The corresponding development with the weight increase in the cerebrum can be seen in the growing child's behaviors. At birth, the child can only cry when s/he is unhappy or in need of care, but eventually, when held and rocked, the baby will learn to stop crying. By three months, the baby will begin to express him/herself through laughter and at six months begin to coo. Then, the child will eventually begin to speak.

In the first year of life, the child walk is not yet stable and s/he cannot care for his/her bowel movements and must wear a diaper. On the other hand, s/he is able to understand to a considerable degree, when adults speak to them, they are able to pick up a few words, recognize and enjoy music and even watch television. I believe that we do not teach our children to walk right away, because this sensitive period when the cerebrum is developing is an important stage in teaching our children many things as well as affording time for the important mother-child interactions.

The weight of the reproductive organs in both the male and female is small relative to body weight until adolescence. However, in adolescence these organs grow rapidly and soon reach adult size in this growth period. This is the nature's way of adjusting the timing of these organs' growth and emotional and physical development so that the physical functions, physical strength and stamina, and emotional readiness are in full balance with each other.

The lymph glands (the lymphocyte, lymph node etc.) that are critical in the role of immunity for the body, takes on a very unique developmental curve. In other words, it grows very rapidly immediately after birth and becomes about double the size of the adult's in adolescence, when it begins to gradually become smaller. It is conceivable that until adolescence, the lymph glands are programmed to fight off pathogenic germs so that from this period on, the human body is protected to be able to live rather safely from disease. This is called immunological memory. The lymph nodes grow rapidly until the end of adolescence studying the various pathogenic germs that it must fight off. That is why it becomes such a large size in adolescence. This is the mechanism for resisting germs once we are immune to it. When a certain germ invades our body, the lymph nodes program it into the body as needing resistance and when that germ returns, is most often able to fight it off.

The quality of growth must not be ignored in regarding the speed of growth in the development process. For example, in language development, there is a speedy acquisition of vocabulary. Subsequently, language development accelerates although it varies according to this process also varies according to each individual.

The third principle of development is "the direction of development". This is related to the first principle, which is the " order of development".

The fundamental direction is from head to toe. That is, development occurs from close to the head and proceeds down to the lower parts of the body. For example, as I explained in the section about the order of development, motor development begins from eye coordination and moves down to the arms and then the hands. This is deeply related to the myelination of the central and peripheral nerves. Myelination is the process where the axon of the nerve fibers are overlapped with the Schwann cells where electricity flows, and acts as an insulation system.

Following is the argument that development ripens from eventually going from the central parts of the body to the peripheral. The development of the movement of the upper arms proceeds that of the fingertips, which is a good example of what I mean here.

Furthermore, there is the direction of development from mass activity to specific activity. A representative example of this phenomenon is the development of the baby's actions. The newborn's movements are clumsy and general in the beginning, but gradually, the movements become more refined and the baby is able to express his/her needs and wants more particularly with a specific purpose in mind. If we can foster these developments well, and with the proper training, one can become able to play the piano or the violin.

Finally, there is the direction called individualization. As development progresses, individualization becomes more distinct leading to solid personality formations. This phenomenon is the one that accounts for individual variance which increases as development progresses. Structurally and functionally, heredity and environmental factors affect personality development. Thus, as age increases, the variance in individual personality differences seems to increase as well.
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