infancy


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infancy,

stage of human development lasting from birth to approximately two years of age. The hallmarks of infancy are physical growth, motor development, vocal development, and cognitive and social development.

Physical Growth

The first year is characterized by rapid physical growth. A normal baby doubles its birth weight in six months and triples it in a year. During that time, there is great expansion of the head and chest, thus permitting development of the brain, heart, and lungs, the organs most vital to survival. The bones, which are relatively soft at birth, begin to harden, and the fontanelles, the soft parts of the newborn skull, begin to calcify, the small one at the back of the head at about 3 months, the larger one in front at varying ages up to 18 months. Brain weight also increases rapidly during infancy: by the end of the second year, the brain has already reached 75% of its adult weight.

Growth and size depend on environmental conditions as well as genetic endowment. For example, severe nutritional deficiency during the mother's pregnancy and in infancy are likely to result in an irreversible impairment of growth and intellectual development, while overfed, fat infants are predisposed to become obese later in life. Human milk provides the basic nutritional elements necessary for growth; however, in Western cultures supplemental foods are generally added to the diet during the first year.

The newborn infant sleeps almost constantly, awakening only for feedings, but the number and length of waking periods gradually increases. By the age of three months, most infants have acquired a fairly regular schedule for sleeping, feeding, and bowel movements. By the end of the first year, sleeping and waking hours are divided about equally.

Motor Development

Development of motor activity follows a fairly standard sequence. The infant learns to lift its head, to turn over on its back, and to develop the muscular coordination for refined, visually directed hand movements and for sitting, crawling, standing, and walking, generally in that order. Motor development proceeds more rapidly than actual physical growth by the beginning of the second year. Bowel and bladder control is sometimes possible after 18 months. However, many normal, healthy infants show delayed response in one or several developmental activities, or may apparently skip a stage altogether.

Vocal Development

An infant's early crying sounds are largely limited to frontal vowels, such as in "dada," and a few consonants; the remaining vowel and consonant sounds gradually appear, first produced in a babbling manner, and the first meaningful words may appear at ten months. By the end of the second year, the infant's active vocabulary may reach 250 words. One of the key reasons infants can produce more sounds is the developing larynx, or voice box, which "descends" between the ages of 1 1-2 to 2 years. Thus, as the infant's vocal tract develops, the wider the range of sounds. See voicevoice,
sound produced by living beings. The source of the sound in human speaking and singing is the vibration of the vocal cords, which are inside the larynx, and the production of the sounds is called phonation.
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Cognitive and Social Development

Studies indicate that certain cognitive processes, the order of which is largely biologically controlled, begin as early as two months after birth. Up to six months of age, differences in motor and conceptual development are generally independent of the infant's rearing conditions and culture, but by one year of age, cultural differences affect intellectual development. From the early months on, the infant forms attachments to those who care for him or her, and on the basis of their behavior, begins to develop expectations of gratification, e.g., adult responses to cries of distress. Social smiling appears early, and by the latter part of the first year the baby may depend on the presence of familiar faces and become apprehensive in the presence of strangers.

Bibliography

See the many studies by child psychologist J. Piaget; J. Kagan et al., Infancy: Its Place in Human Development (1978); T. B. Brazalton, Infants and Mothers (rev. ed. 1983); J. G. Bremner, Infancy (1988).

infancy

[′in·fən·sē]
(geology)
The initial (youthful) or very early stage of the cycle of erosion characterized by smooth, nearly level erosional surfaces dissected by narrow stream gorges, numerous depressions filled by marshy lakes and ponds, and shallow streams. Also known as topographic infancy.

infancy

the period of life prior to attaining legal majority (reached at 21 under common law, at 18 by statute); minority nonage
References in classic literature ?
And now, when weighed down by the pains and aches of old age, when the head inclines to the feet, when the beginning and ending of human existence meet, and helpless infancy and painful old age combine to- gether--at this time, this most needful time, the time for the exercise of that tenderness and affection which children only can exercise towards a declining parent--my poor old grandmother, the devoted mother of twelve children, is left all alone, in yonder little hut, before a few dim embers.
Looking back, as I was saying, into the blank of my infancy, the first objects I can remember as standing out by themselves from a confusion of things, are my mother and Peggotty.
In his infancy he had been placed in the charge of one of the great ladies of the Court, who, according to the prevailing custom, acted first as his head nurse and then as his governess.
Firman, in 1879; but he became a farmer and forsook his invention in its infancy.
And because we have all to pass through a state of infancy to manhood, and have been of necessity, for a length of time, governed by our desires and preceptors (whose dictates were frequently conflicting, while neither perhaps always counseled us for the best), I farther concluded that it is almost impossible that our judgments can be so correct or solid as they would have been, had our reason been mature from the moment of our birth, and had we always been guided by it alone.
Should they prove deformed or defective in any way they are promptly shot; nor do they see a tear shed for a single one of the many cruel hardships they pass through from earliest infancy.
For it seemed as if other voices--familiar in infancy, and unforgotten through many wanderings, and in all the vicissitudes of her heart and fortune--were mingling with the accents of the prayer.
So sweet a child she was, that it seemed fit her infancy should be immortal.
Looking back after much love and much trouble, the instinct of primitive man, who seeks to personify the forces of Nature for his affection and for his fear, is awakened again in the breast of one civilized beyond that stage even in his infancy.
he said, trying to smile, when Addy stretched out his arms--ready, with the usual baseness of infancy, to give up his Uncle Seth at once, now there was some rarer patronage at hand.
From his infancy he had, with calculation beyond his age, lent his name and complaisance to the follies of the Comte de Guiche.
This is almost realizing the fable of the centaurs; nor can we wonder at the equestrian adroitness of these savages, who are thus in a manner cradled in the saddle, and become in infancy almost identified with the animal they bestride.