chapter 5 physical development in infancy. black hawk college chapter 52

Chapter 5

Physical Development in

Infancy

Black Hawk College Chapter 5 2

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The Cephalocaudal Pattern

• The cephalocaudal pattern is the sequence in which the greatest growth always occurs at the top—the head— with physical growth in size, weight, and feature differentiation gradually working its way down from top to bottom.


Aspects of the Cephalocaudal Pattern

• This same pattern occurs in the head area, because the top parts of the head—the eyes and brain—grow faster than the lower parts.

• An extraordinary proportion of the total body is occupied by the head during prenatal development and early infancy.

• Sensory and motor development proceed according to the cephalocaudal principle.


The Proximodistal Pattern

• The sequence in which growth starts at the center of the body and moves toward the extremities.


Height

• The average North American newborn is 20 inches long.

• Ninety-five percent of full-term newborns are 18-22 inches long.

• Infants grow about 1 inch per month during the first year, reaching approximately 1½ times their birth length by their first birthday.

• Infants’ rate of growth is considerably slower in the second year of life.

• At age 2, the average infant is 32-35 inches long.


Weight

• The average North American baby weighs 7½ pounds.• Ninety-five percent of full-term newborns weigh between 5½ and

10 pounds.• In the first several days of life, most newborns lose 5-7 percent of

their body weight before they adjust to neonatal feeding.• Infants gain 5-6 ounces per week during the first month.• They have doubled their birthweight by the age of 4 months.• They have nearly tripled their birthweight by their first birthday.• During the second year of life they gain a quarter to half a pound

per month.• At 2 years of age they have reached about one-fifth of their adult

weight.


The Brain

• The Brain’s Development

• Measuring the Brain’s Activity in Research on Infant Memory

• The Brain’s Hemispheres

• Early Experience and the Brain


Definition of a Neuron

• A nerve cell that handles information processing at the cellular level


The Brain’s Development• At birth, the newborn’s brain is about 25% of its

adult weight and, by the second birthday, it is about 75% of its adult weight.

• Newborns have all of the neurons they will ever have—about 100 billion.

• Some areas of the brain, such as the primary motor areas, develop earlier than others, such as the primary sensory areas.

• Among the most dramatic changes in the brain in the first 2 years of life are the spreading connections of dendrites to each other.


Myelination• The process of encasing axons with fat cells.• Myelination both insulates the nerve cells and helps

nerve impulses travel faster.• A myelin sheath (a layer of fat cells) encases most

axons.• Myelination for visual pathways occurs rapidly after

birth and is completed in the first 6 months.• Auditory myelination is not completed until 4-5

years of age.• Some aspects of myelination continue into

adolescence.


Measuring the Brain’s Activity in Research on Infant Memory

• Even the latest technologies don’t enable researchers to make out fine details in brain imaging of babies, and they often can’t be used with babies.

• Charles Nelson is pioneering informative infant-brain research using 128 electrodes attached to babies’ scalps.

• Nelson has found that newborns produce distinctive brain waves that reveal they can distinguish their mother’s voices from another woman’s, even while they’re asleep.

• He has also found that by 8 months, babies can distinguish a picture of a wooden toy they were allowed to feel, but not see, from pictures of other toys.

• This coincides with the development of the hippocampus.


The Brain’s Hemispheres• The highest level of the brain, the cerebral cortex, is

divided into two halves, or hemispheres.• There continues to be considerable interest in the

degree to which each hemisphere is involved in various aspects of thinking, feeling, and behavior.

• The most extensive research on the brain’s hemispheres has focused on language.

• At birth, the hemispheres have already started to specialize, with newborns showing greater electrical brain activity in the left hemisphere than the right hemisphere when listening to speech.


Definition of Lateralization

• The specialization of functions in one hemisphere of the cerebral cortex or the other


Early Experience and the Brain

• Starting shortly after birth, a baby’s brain produces trillions more connections between neurons than it can possibly use.

• The brain eliminates connections that are seldom or never used—continuing at least until 10 years of age.

• Current belief is that the infant’s brain is waiting for experiences to determine how connections are made.

• Before birth, genes appear to direct how the brain establishes basic wiring patterns.

• After birth, environmental experiences are important in the brain’s development.


Infant States• Developmentalists are interested in infants’ states of

consciousness, or levels of awareness.• Classifying infant states has helped researchers

identify many aspects of infant development, such as the sleep-waking cycle.

• Newborns sleep 16-17 hours a day with individual variations.

• Most 1-month-olds begin sleeping longer at night.• Most 4-month-olds usually have moved closer to

adultlike sleep patterns.• Researchers have found cultural variations in infant

sleeping patterns.


REM (Rapid Eye Movement) Sleep

• A recurring sleep stage during which vivid dreams commonly occur.

• Most adults spend about one-fifth of their night in REM sleep.

• Infants spend about one-half of their sleep in REM sleep and it begins their sleep cycle.

• By 3 months the percentage of REM sleep falls to 40%, and it no longer starts their sleep cycle.

• REM sleep is thought to promote the brain’s development in infancy.


A Classification Scheme for Infant States

• No REM sleep• Active sleep without REM• REM sleep• Indeterminate sleep• Drowsy• Inactive alert• Active awake• Crying


Shared Sleeping• There exists considerable variation across

cultures in newborns’ sleeping arrangements.• Some child experts believe shared sleeping is

beneficial with regard to promoting breast feeding, responsiveness to infant crying, and detection of dangerous breathing pauses.

• The American Academy of Pediatrics Task Force on Infant Positioning and SIDS recommends against shared sleeping due to an increased risk of sudden infant death syndrome (SIDS).

• Shared sleeping remains a controversial issue.


SIDS• Sudden infant death syndrome is a condition that occurs

when infants stop breathing, usually during the night, and suddenly die without apparent cause.

• It is the highest cause of infant death in the U.S. with approximately 13% of all infant deaths due to SIDS.

• Risk of SIDS is highest at 4-6 weeks of age.• Some researchers believe that an inability to swallow

effectively in the prone sleeping position is an important factor in SIDS.

• The American Academy of Pediatrics has recommended since 1992 that infants sleep on their backs.


Risk Factors for SIDS• Low-birthweight infants are 5 to 10 times more likely to die of

SIDS.• Twins and triplets, even at normal birthweight, are twice as likely

to die of SIDS.• After one twin dies, the surviving twin has an increased risk of

dying from SIDS.• Infants whose siblings have died of SIDS are two to four times

as likely to die of it.• Six percent of infants with sleep apnea, a temporary cessation

of breathing in which the airway is completely blocked, usually for 10 seconds or longer, die of SIDS.

• African American and Eskimo infants are four to six times as likely as all others to die of SIDS.

• SIDS is more common in lower socioeconomic groups.• SIDS is more common in infants who are passively exposed to

cigarette smoke.• Soft bedding is not recommended.


Nutrition

• Nutritional Needs and Eating Behavior

• Breast- Versus Bottle-Feeding

• Malnutrition in Infancy


Nutritional Needs and Eating Behavior

• The importance of adequate energy and nutrient intake consumed in a loving and supportive environment during the infant years cannot be overstated.

• Nutritionists recommend that infants consume approximately 50 calories per day for each pound they weigh—more than twice an adult’s requirement per pound.

• A controversy has existed over whether infants should be fed on a regular schedule (e.g., 4 ounces of formula every 6 hours), or fed on demand (determined by the infant).

• Diets designed for adult weight loss and prevention of heart disease may actually retard growth and development in babies, who need high-energy, high-calorie food.


Breast- Versus Bottle-Feeding• Human milk, or alternative formula, is the baby’s source of

nutrients and energy for the first 4 to 6 months of life.• For years, debate has focused on whether breast-feeding

is better for the infant than bottle-feeding.• The growing consensus is that breast-feeding is better for

the baby’s health.• The American Pediatric Association strongly endorses

breast-feeding throughout the first year of life.• Mothers least likely to breast feed are those who work full-

time outside the home, mothers under 25, mothers without a high school education, African-American mothers, and mothers in low-income circumstances.

• Some researchers have found no psychological differences between breast-fed and bottle-fed infants.


Benefits of Breast Feeding

• Appropriate weight gain• Fewer allergies• Prevention or reduction of diarrhea, respiratory

infections, bacterial and urinary tract infections, and otitis media

• Bone density in childhood and adulthood• Reduced childhood cancer and reduced incidence of

breast cancer in mothers and their female offspring• Lower incidence of SIDS• Neurological and cognitive development• Visual acuity


Malnutrition in Infancy

• In many of the world’s developing countries, mothers used to breast-feed their infants for at least 2 years.

• To become more modern, they’ve stopped breast-feeding much earlier and replaced it with bottle-feeding.

• Weaning from breast milk to inadequate nutrients, such as unsuitable and unsanitary cow’s milk formula, can lead to conditions called marasmus and kwashiorkor.

• Even if it’s not fatal, severe and lengthy malnutrition is detrimental to physical, cognitive, and social development.

• In some cases, even moderate malnutrition can produce subtle difficulties in development.


Marasmus and Kwashiorkor• Marasmus is a wasting away of body tissues in the

infant’s first year, caused by severe protein-calorie deficiency.

• Infant becomes grossly underweight and muscles atrophy.

• Kwashiorkor is a condition caused by a deficiency in protein in which the child’s face, legs, and abdomen swell with water.

• It causes a child’s vital organs to collect the nutrients that are present and deprive other parts of the body of them.

• The child’s hair also becomes thin, brittle, and colorless.• The child’s behavior also often becomes listless.


Toilet Training

• The ability to control elimination depends on both muscular maturation and motivation.

• Children must be able to control their muscles to eliminate at the appropriate time, and they must want to eliminate in the toilet or potty rather than in their pants.

• There are no data on the optimal time of toilet training, but developmentalists argue that when it is initiated, it should be accomplished in a warm, relaxed, supportive manner.

• In North American culture, being toilet trained is a skill that is expected to be attained by 3 years of age.

• By the age of 3, 84% of children are dry throughout the day, and 66% are dry throughout the night.


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Reflexes

• Reflexes, genetically carried survival mechanisms, govern the newborn’s movements.

• They are automatic and beyond the newborn’s control; built-in reactions to stimuli.

• In these reflexes, infants have adaptive responses to their environment before they’ve had the opportunity to learn.

• Reflexes may serve as important building blocks for subsequent purposeful motor activity.


The Sucking Reflex• Occurs when newborns automatically

suck an object placed in their mouth.• Enables newborns to get nourishment before

they have associated a nipple with food.• Present at birth; later disappears at 3-4 months.• Most newborns take several weeks to establish

a sucking style that is coordinated with the way the mother is holding the infant, the way the milk is coming out of the bottle or breast, and the infant’s sucking speed and temperament.


The Rooting Reflex

• The rooting reflex occurs when the infant’s cheek is stroked or the side of the mouth is touched.

• In response, the infant turns its head toward the side that was touched in an apparent effort to find something to suck.

• The rooting reflex disappears when the infant is 3-4 months old, as it is replaced by the infant’s voluntary eating.


The Moro Reflex• The Moro reflex is a neonatal startle response

that occurs in response to a sudden, intense noise or movement.

• When startled, a newborn arches its back, throws back its head, and flings out its arms and legs.

• The newborn then rapidly closes its arms and legs to the center of its body.

• Steady pressure on any part of the infant’s body calms the infant after it has been startled.

• Tends to disappear around 3-4 months of age.


The Grasping Reflex

• Occurs when something touches the infant’s palms.

• Infant responds by grasping tightly.• Replaced around the end of the third month

by voluntary grasps, often produced by visual stimuli.


Gross Motor Skills• Gross motor skills involve large muscle activities, such as

moving one’s arms and walking.• These are the most dramatic and observable changes in

the infant’s first year of life.• The actual month at which gross motor milestones occur

varies by as much as 2 to 4 months.• The sequence of accomplishments is quite uniform.• In the second year of life toddlers become more motorically

skilled and mobile.• Development experts believe that motor activity during the

second year is vital to the child’s competent development, and that few restrictions (other than for safety) should be placed on their motoric adventures.


Gross Motor Milestones• Birth - no appreciable coordination of the chest or arms• 1st month - lift head from a prone position• 3 months - hold chest up and use arms for support• 3-4 months - roll over• 4-5 months - support some weight with legs• 6 months - sit without support• 7-8 months - crawl and stand without support• 8 months - pull up to a standing position• 10-11 months - walk using furniture for support (cruising)• 12-13 months - walk without assistance• 13-18 months - pull a toy, climb some steps• 18-24 months - walk quickly, run stiffly, squat, kick, jump


Fine Motor Skills• Fine motor skills involve more finely-tuned movements,

such as finger dexterity.• Infants have hardly any control over fine motor skills at

birth.• They do have many components of what later become

finely coordinated arm, hand, and finger movements.• The development of reaching and grasping becomes more

refined during the first 2 years of life.• Initially, infants show only crude shoulder and elbow

movements, but later they show wrist movements, hand rotation, and coordination of the thumb and forefinger.

• The maturation of hand-eye coordination over the first 2 years is reflected in the improvement of fine motor skills.


Developmental Biodynamics

• Developmental biodynamics seeks to explain how motor behaviors are assembled for perceiving and acting.

• It is an outgrowth of developments in the neurosciences, biomechanics, and the behavioral sciences.

• This view contrasts with the traditional maturational view by proposing that even the universal milestones, such as crawling, reaching, and walking, are learned through a process of adaptation.

• It proposes that the new task, the challenge of the context, rather than prescribed genetic instructions, represents the driving force for change.


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What Are Sensation and Perception?

• Sensation occurs when information interacts with sensory receptors—the eyes, ears, tongue, nostrils, and skin.

• The sensation of hearing occurs when waves of pulsating air are collected by the outer ear and transmitted through the bones of the inner ear to the auditory nerve.

• Perception is the interpretation of what is sensed.• The information about physical events that contact the

ears may be interpreted as musical sounds, human speech, or a jet engine.


Visual Perception

• Visual Acuity and Color

• Visual Preferences

• Depth Perception

• Visual Expectations


Visual Acuity and Color• The newborn’s vision is estimated to be 20/400 to

20/800 on the Snellan chart—about 10-30 times lower than normal adult vision (20/20).

• By 6 months of age vision is 20/100 or better.• By the first birthday, the infant’s vision

approximates that of an adult.• At birth, babies can distinguish green and red.• By 2 months of age, there is adultlike functioning

in all three types (red, blue, green) of color-sensitive receptor (cones).


Visual Preferences

• In 1963 Robert Fantz discovered that infants look at different things for different lengths of time.

• He found that infants preferred to look at patterns rather than at color or brightness.

• Fantz also found that 2-day-old infants look longer at patterned stimuli than at single-colored discs.

• The conclusion is that pattern perception has an innate basis, or at least is acquired after only minimal environmental experience.


Depth Perception• Gibson and Walk conducted the classic “visual cliff”

experiment in 1960 to assess how early infants could perceive depth.

• They placed a piece of glass over a drop-off patterned the same as the table next to it.

• Mothers coaxed their infants from across the “cliff” to see if they would crawl on the glass over the drop-off.

• Most infants would not crawl out onto the glass, choosing instead to remain on the shallow side—indicating they could perceive depth.

• Problems with drawing a conclusion as to how early depth perception is present include the fact that very young infants can’t crawl—a requirement of the study.


Visual Expectations• Infants not only see forms and figures at an early

age, but develop expectations about future events in their world.

• When presented with a predictable sequence of pictures, 3-month-olds began to anticipate the location of the pictures.

• These infants formed these expectations in less than 1 minute.

• Other studies have demonstrated that by 4 months of age, infants can recognize where a moving object is when it has left their visual field and can infer where it should be when it comes into their sight again.


Other Senses

• Hearing• Touch • Pain• Smell • Taste


Hearing• In the last few months of pregnancy, a fetus can hear sounds (the

mother’s voice, music, etc.)• After birth, infants responded in a certain way when mothers read

them a story that they had read to them during the 6 weeks prior to birth.

• This finding suggests that the infants recognized the story’s pattern and tone—something they’d only been exposed to prenatally.

• Infants can hear immediately after birth, but a sound must be louder to be heard by a newborn than an adult.

• As infants age from 8 to 28 weeks, they become more proficient in localizing sounds.

• Infants are born with the ability to discriminate speech sounds from any language, but without constant exposure, they lose the ability by their first birthday.


Touch and Pain• Newborns respond to touch, particularly with the

sucking and rooting reflex.• An important ability that develops during the first year

is to connect information about vision with information about touch.

• It used to be believed that newborns were impervious to pain, but it is now known that it is not true.

• Newborn males show a higher level of cortisol (a stress indicator) after a circumcision than prior to the surgery.

• Anesthesia is now used in some cases of circumcision.


Smell and Taste• Newborns can differentiate odors.• They appear to like vanilla and strawberry scents, but

not those of rotten eggs and fish.• Infants do require several days of experience to show

preference for the scent of their mother’s breast pad.• Sensitivity to taste may be present prior to birth due to

increased swallowing of a near-term fetus when saccharin was added to the amniotic fluid.

• Two-hour-old newborns made different facial expressions when they tasted sweet, sour, and bitter solutions.

• At 4 months of age, infants prefer salty tastes, which newborns found aversive.


Intermodal Perception

• The ability to relate and integrate information about two or more sensory modalities, such as vision and hearing.

• Various studies have found that infants as young as 3½ months not only can coordinate visual-auditory information, but prefer to experience what they see together with what they hear.


Perceptual-Motor Coupling and Unification

• There is an increasing belief that perceptual and motor development do not occur in isolation from one another but, rather, are coupled.

• Individuals perceive in order to move and move in order to perceive.

chapter 5 physical development in infancy. black hawk college chapter 52

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