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A human infant

In basic English usage, an infant is defined as a human child at the youngest stage of life, especially before they can walk or simply a child before the age of one.[1]

The term "infant" derives from the Latin word in-fans, meaning "unable to speak." There is no exact definition for infancy. Quite often babies are called infants until they reach the age of one. Babies are traditionally called "toddlers" when they start to walk, whether or not they have reached this age. Daycares with an "infant room" often call all children in it "infants" even if they are older than a year and/or walking; they sometimes use the term "walking infant".

"Infant" is also a legal term with the meaning of minor[2]; that is, any child under the age of legal adulthood. A human infant less than a month old is a newborn infant or a neonate.[3] The term "newborn" includes premature infants, postmature infants and full term newborns.

The newborn


Newborn infant, just seconds after delivery.

A newborn's shoulders and hips are narrow, the abdomen protrudes slightly, and the arms and legs are relatively short. The average weight of a full-term newborn is approximately 7 ½ pounds (3.2 kg), but is typically in the range of 5.5–10 pounds (2.7–4.6 kg). The average total body length is 14–20 inches (35.6–50.8 cm), although premature newborns may be much smaller. The Apgar score is a measure of a newborn's transition from the womb during the first minutes of life.

A newborn's head is very large in proportion to the rest of the body, and the cranium is enormous relative to his or her face. While the adult human skull is about 1/8 of the total body length, the newborn's is about 1/4. At birth, many regions of the newborn's skull have not yet been converted to bone, leaving "soft spots" known as fontanels. The two largest are the diamond-shaped anterior fontanel, located at the top front portion of the head, and the smaller triangular-shaped posterior fontanel, which lies at the back of the head. Later in the child's life, these bones will fuse together in a natural process. A protein called noggin is responsible for the delay in an infant's skull fusion.[4]

During labour and birth, the infant's skull changes shape to fit through the birth canal, sometimes causing the child to be born with a misshapen or elongated head. It will usually return to normal on its own within a few days or weeks. Special exercises sometimes advised by physicians may assist the process.

Some newborns have a fine, downy body hair called lanugo. It may be particularly noticeable on the back, shoulders, forehead, ears and face of premature infants. Lanugo disappears within a few weeks. Likewise, not all infants are born with lush heads of hair. Some may be nearly bald while others may have very fine, almost invisible hair. Some babies are even born with a full head of hair. Amongst fair-skinned parents, this fine hair may be blond, even if the parents are not. The scalp may also be temporarily bruised or swollen, especially in hairless newborns, and the area around the eyes may be puffy.

Immediately after birth, a newborn's skin is often grayish to dusky blue in color. As soon as the newborn begins to breathe, usually within a minute or two, the skin's color returns to its normal tone. Newborns are wet, covered in streaks of blood, and coated with a white substance known as vernix caseosa, which is hypothesised to act as an antibacterial barrier. The newborn may also have Mongolian spots, various other birthmarks, or peeling skin, particularly on the wrists, hands, ankles, and feet.

A newborn's genitals are enlarged and reddened, with male infants having an unusually large scrotum. The breasts may also be enlarged, even in male infants. This is caused by naturally-occurring maternal hormones and is a temporary condition. Females (and even males) may actually discharge milk from their nipples (sometimes called witch's milk), and/or a bloody or milky-like substance from the vagina. In either case, this is considered normal and will disappear in time.

The umbilical cord of a newborn is bluish-white in color. After birth, the umbilical cord is normally cut, leaving a 1–2 inch stub. The umbilical stub will dry out, shrivel, darken, and spontaneously fall off within about 3 weeks. Occasionally, hospitals may apply triple dye to the umbilical stub to prevent infection, which may temporarily color the stub and surrounding skin purple.

Newborns lose many of the above physical characteristics quickly. Thus prototypical older babies look very different. While older babies are considered "cute", newborns can be "unattractive" by the same criteria and first time parents may need to be educated in this regard.

The newborn's senses

Main article: Infant perception

Proprioception in the infant

As an infant's vision develops, he or she may seem preoccupied with watching surrounding objects and people.

Newborns can feel all different sensations, but respond most enthusiastically to soft stroking, cuddling and caressing. Gentle rocking back and forth often calms a crying infant, as do massages and warm baths. Newborns may comfort themselves by sucking their thumb, or a pacifier. The need to suckle is instinctive (see Suction in biology) and allows newborns to feed.

Main article: Proprioception in the infant

Vision in the infant

Newborn infants have unremarkable vision, being able to focus on objects only about 18 inches (45 cm) directly in front of their face. While this may not be much, it is all that is needed for the infant to look at the mother's face when breastfeeding. When a newborn is not sleeping, or feeding, or crying, he or she may spend a lot of time staring at random objects. Usually anything that is shiny, has sharp contrasting colors, or has complex patterns will catch an infant's eye. However, the newborn has a preference for looking at other human faces above all else. (see also: infant metaphysics)

Auditory perception in the infant

While still inside the mother, the infant could hear many internal noises, such as the mother's heartbeat, as well as many external noises including human voices, music and most other sounds. Therefore, although a newborn's ears may have some catarrh and fluid, he or she can hear sound from before birth. Newborns usually respond to a female voice over a male voice. This may explain why people will unknowingly raise the pitch of their voice when talking to newborns. The sound of other human voices, especially the mother's, can have a calming or soothing effect on the newborn. Conversely, loud or sudden noises will startle and scare a newborn.

Main article: Auditory perception at birth
Main article: Speech perception in infants

Gustation in the infant

Newborns can respond to different tastes, including sweet, sour, bitter, and salty substances, with a preference toward sweets.

Main article: Gustation in the infant

Olfaction in the infant

A newborn has a developed sense of smell at birth, and within the first week of life can already distinguish the differences between the mother's own breast milk and that of another female.

Main article: Olfaction in the infant

Infant mental health

Research has shown that support for parents during the first year can significantly increase the proportion of infants securely attached to their parents with lasting benefits for their subsequent development. Similarly Post Natal Depression can be alleviated so that its potentially adverse effect in infant development is reduced. Early intervention can often prevent later mental health problems. A good beginning for young families is a protective factor in coping with stress.

Main article: Infant mental health

Infant attachment

Main article: Attachment theory

Attachment theory is primarily an evolutionary and ethological theory whereby the infant or child seeks proximity to a specified attachment figure in situations of alarm or distress, for the purpose of survival. The forming of attachments is considered to be the foundation of the infant/childs's capacity to form and conduct relationships throughout life. Attachment is not the same as love and/or affection although they often go together. Attachment and attachment behaviors tend to develop between the age of 6 months and 3 years. Infants become attached to adults who are sensitive and responsive in social interactions with the infant, and who remain as consistent caregivers for some time. Parental responses lead to the development of patterns of attachment which in turn lead lead to 'internal working models' which will guide the individuals feelings thoughts and expectations in later relationships.[5] There are a number of attachment 'styles' namely 'secure', 'anxious-ambivalent', 'anxious-avoidant', (all 'organized') and 'disorganized', some of which are more problematical than others. A lack of attachment or a seriously disrupted capacity for attachment could potentially amount to serious disorders.

This stage specific care

Infant mortality

Main article: Infant mortality

Infant mortality is the death of an infant in the first year of life. Infant mortality can be subdivided into neonatal death, referring to deaths in the first 27 days of life, and post-neonatal death, referring to deaths after 28 days of life. Major causes of infant mortality include dehydration, infection, congenital malformation, and SIDS.

This epidemiological indicator is recognized as a very important measure of the level of health care in a country because it is directly linked with the health status of infants, children, and pregnant women as well as access to medical care, socioeconomic conditions, and public health practices.

Care and feeding

Main article: Childcare

Feeding is typically done by breastfeeding, or bottle feeding with expressed breast-milk or with a special, heavily processed industrial milk product, "infant formula".[6] Infants have a sucking instinct allowing them to extract the milk from the nipples of the breasts or the nipple of the baby bottle, as well as an instinctive behavior known as rooting with which they seek out the nipple. Sometimes a wet nurse is hired to feed the infant. Breastfeeding provides infants with many natural immune substances and isolates the infant from most bacteria or other contaminants in the local water supply. Infant formula does not provide these immune substances and in places with poor quality water supply, subjects the infant to an increased risk of disease. Only breast milk is considered to have all that an infant requires to grow normally (thrive), although formula undergoes frequent alterations in order to more closely imitate human milk. [7]

As infants age, and their appetites grow, many parents choose from a variety of commercial, ready-made baby foods to feed the child, while others adapt their usual meals for the dietary needs of their child.

Infants are incontinent, therefore diapers are generally used in industrialized countries, while methods similar to elimination communication[8] are common in third world countries. Practitioners of these techniques assert that babies can control their bodily functions at the age of six months and that they are aware when they are urinating at an even earlier age. Babies can learn to signal to the parents when it is time to urinate or defecate by turning or making noises. Parents have to pay attention to the baby's actions so they can learn the signals.

Babies cannot walk, although more mature infants may crawl or scoot; baby transport may be by perambulator (stroller or buggy), on the back or in front of an adult in a special carrier, cloth or cradle board, or simply by being carried in the arms. Infants cry as a form of basic instinctive communication to their parents when in need of feeding, in discomfort or feeling neglected.

As is the case with most other young children, infants are usually treated as special persons. Their social presence is different from that of adults, and they may be the focus of attention. Fees for transportation and entrance fees at locations such as amusement parks or museums are often waived. This special attention will wear out as the child grows older.

Most industrialized countries have laws requiring infants to be placed in special seats when in motor vehicles. See child safety seat for more information.

Common care issues for infants:

See also


  1. Results for "infant".
  2. "Infant". Merriam-Webster online dictionary. Merriam-Webster. URL accessed on 2007-03-27.
  3. "Neonate". Merriam-Webster online dictionary. Merriam-Webster. URL accessed on 2007-03-27.
  4. Warren SM, Brunet LJ, Harland RM, Economides AN, Longaker MT (2003-04-10). The BMP antagonist noggin regulates cranial suture fusion. Nature 422 (6932): 625-9. PMID 12687003.
  5. Bretherton,I. and Munholland,K., A. Internal Working Models in Attachment Relationships: A Construct Revisited. Handbook of Attachment:Theory, Research and Clinical Applications 1999eds Cassidy,J. and Shaver, P., R. Guilford press ISBN 1-57230-087-6
  6. Powdered Infant Formula: An Overview of Manufacturing Processes. Food and Drug Administration. URL accessed on 2007-03-27.
  7. Carver, Jane D. (June 2003). Advances in nutritional modifications of infant formulas. Am. J. Clin. Nutr. 77 (6): 1550-1554. PMID 12812153.
  8. Elimination Communication. Yahoo! Groups. URL accessed on 2007-03-27.
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  • Simkin, Penny; et al. (1992 (late 1991)). Pregnancy, Childbirth and the Newborn: The Complete Guide, Meadowbook Press. ISBN 0-88166-177-5.
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See also

An infant in a neonatal intensive care unit

External links

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Stages of human development
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