Chapter 2: Infancy

Module 2.1Physical Development

in Infancy

Physical Growth

• Rapid growth during first two years• Birth: around 7 pounds; 20 inches• 5 months: doubled birth weight• 12 months: tripled birth weight; 30 inches• 24 months: slows; 4x birth weight; 36 inches

Head Growth

• Not all parts of an infant’s body grow at the same rate.

• At birth the head accounts for one-quarter of the newborn’s entire body size.

• During the first 2 years of life, the rest of the body begins to catch up.

• By the age of 2 the baby’s head is only one-fifth of body length, and by adulthood it is only one-eighth.

Head Growth (cont.)

Gender and Ethnic Differences in Weight and Length

• Girls generally are slightly shorter and weigh slightly less than boys, and these differences remain throughout childhood (disparities become considerably greater during adolescence).

• Asian infants tend to be slightly smaller than North American Caucasian infants, and African-American infants tend to be slightly bigger than North American Caucasian infants.

Principles of Growth• Cephalocaudal principle - states that growth follows a

direction and pattern that begins with the head and upper body parts and then proceeds to the rest of the body.

• Proximodistal principle - states that development proceeds from the center of the body outward.

• Principle of hierarchical integration - states that simple skills typically develop separately and independently. Later these simple skills are integrated into more complex ones.

• Principle of independence of systems - suggests that different

body systems grow at different rates.

Nervous System and Brain

• Nervous system comprises the brain and the nerves that extend throughout the body

• Neurons are the basic cells of the nervous system

Nervous System and Brain (cont.)

• Like all cells in the body, neurons have a cell body containing a nucleus. • But unlike other cells, neurons have a distinctive ability: They can

communicate with other cells, using a cluster of fibers called dendrites at one end.

• Dendrites receive messages from other cells. • At their opposite end, neurons have a long extension called an

axon, the part of the neuron that carries messages destined for other neurons.

• Neurons do not actually touch one another. Rather, they communicate with other neurons by means of chemical messengers, neurotransmitters, that travel across the small gaps, known as synapses, between neurons.

A Bit about Brains

The Brain Stem

The Brain Stem (cont.)

The Brain Stem (cont.)

The Brain Stem (cont.)

The Limbic System

The Cerebral Cortex

Brain Growth

• Birth: – 100-200 billion

neurons– Relatively few

neurons-neuron connections

• During first two years:– Billions of new

connections established and become more complex

Brain Growth (cont.)

• Birth: Neurons multiply at an amazing rate prior to birth. At some points in prenatal development, cell division creates some 250,000 additional neurons every minute.

• By year 2: The intricacy of neural connections continues to increase throughout life. In fact, in adulthood a single neuron is likely to have a minimum of 5,000 connections to other neurons or other body parts.

Brain Growth and Function Synaptic pruning• Unused neurons are eliminated• Allows established neurons to build more elaborate communication

networks with other neurons• Development of nervous system proceeds most effectively through loss of

cells• Neurons that do not become interconnected with other neurons as the infant’s

experience of the world increases become unnecessary. • They eventually die out, increasing the efficiency of the nervous system.

Myelin• Axons of neurons become coated with myelin, a fatty substance that, like

the insulation on an electric wire, provides protection and speeds the transmission of nerve impulses.

• Contributes to increased weight of brain• Even though many neurons are lost, the increasing size and complexity of the remaining ones

contribute to impressive brain growth. • A baby’s brain triples its weight during his or her first 2 years of life, and it reaches more than

three-quarters of its adult weight and size by the age of 2.

Brain Growth and Function (cont.)

• Neurons reposition themselves with growth, becoming arranged by function

Cerebral cortex• Some move into the cerebral cortex, the upper layer of the

brain, while others move to subcortical levels, which are below the cerebral cortex.

• As time passes, however, the cells in the cerebral cortex, which are responsible for higher-order processes such as thinking and reasoning, become more developed and interconnected.

Subcortical levels - The subcortical levels, which regulate such fundamental activities as breathing and heart rate, are the most fully developed at birth.

Shaken Baby Syndrome

– Brain sensitive to many forms of injury

– Shaking can lead to brain rotation within skull• Blood vessels tear causing severe medical

problems, long-term disabilities, and sometimes death

Environmental Influences on Brain Development

• Plasticity - the degree to which a developing structure or behavior is modifiable due to experience

• Sensitive period is a specific, but limited, time, usually early in an organism’s life, during which the organism is particularly susceptible to environmental influences relating to some particular facet of development.

Daily Activity of Infants

• These most basic activities are controlled by a variety of bodily systems.

• Although each of these individual behavioral patterns probably is functioning quite effectively, it takes some time and effort for infants to integrate the separate behaviors. In fact, one of the neonate’s major missions is to make its individual behaviors work in harmony, helping it, for example, to sleep through the night.

Daily Routine:• Wake• Sleep• Eat• Defecate

Infant Sleep

• Major state– 16-17 hours daily (average); wide variations

• Different than adult sleep– 2 hour spurts; periods of wakefulness– Cyclic pattern

• By 16 weeks sleep about 6 continuous hours; by 1 year sleep through night

• By 1 year need about 15 hours sleep• Cyclic pattern: During periods of sleep, infants’

heart rates increase and become irregular, their blood pressure rises, and they begin to breathe more rapidly

Infant Sleep/Wake States

Do babies dream?• Appearance of active sleep periods that are similar to REM

sleep in adults raises the intriguing question of whether infants dream during those periods. No one knows the answer, although it seems unlikely.

• Young infants do not have much to dream about, given their relatively limited experiences.

• Brain waves of sleeping infants appear to be qualitatively

different from those of adults who are dreaming. • It is not until the baby reaches 3 or 4 months of age that the

wave patterns become similar to those of dreaming adults, suggesting that young infants are not dreaming during active sleep—or at least are not doing so in the same way as adults do.

Cultural Practices and Sleep

• Among the Kipsigis of Africa, infants sleep with their mothers at night and are allowed to nurse whenever they wake. In the daytime, they accompany their mothers during daily chores, often napping while strapped to their mothers’ backs. Because they are often out and on the go, Kipsigis infants do not sleep through the night until much later than babies in Western societies, and for the first 8 months of life, they seldom sleep longer than 3 hours at a stretch.

• In comparison, 8-month-old infants in the United States may sleep as long as 8 hours at a time.

Sudden Infant Death Syndrome (SIDS)

• Disorder in which seemingly healthy infants die in their sleep

• Leading cause of death in children under 1 year of age• SIDS strikes about 1 in 1,000 infants in the United

States each year. • Although it seems to occur when the normal

patterns of breathing during sleep are interrupted, scientists have been unable to discover why that might happen.

Sudden Infant Death Syndrome (SIDS) (cont.)

• American Academy of Pediatrics now suggests that babies sleep on their backs rather than on their sides or stomachs—called the back-to-sleep guideline. In addition, they suggest that parents consider giving their babies a pacifier during naps and bedtime.

• More at risk (in general):– Boys– African American infants– Low birthweight– Low APGAR scores– Mother’s smoking– Some brain defects– Child abuse

Declining Rates of SIDS

SIDS is found in children of every race and socioeconomic group and in

children who have had no apparent health problems

Major decline in rate of SIDS after AAP recommendation of putting

babies to sleep on backs!

Back-to-sleep is important!

Reflexes: Inborn Physical Skills

• Reflexes: learned, organized involuntary responses that occur automatically in presence of certain stimuli

A Closer Look at Reflexes

Why do reflexes come and go?• Evolutionary explanations of development attribute the

gradual disappearance of reflexes to the increase in voluntary control over behavior that occurs as infants become more able to control their muscles.• It may be that reflexes form the foundation for future, more

complex behaviors. As these more intricate behaviors become well learned, they encompass the earlier reflexes.

• Perhaps reflexes stimulate parts of the brain responsible for more complex behaviors, helping them develop.

• Although the evidence shows that intensive practice (especially of reflex behaviors) may produce an earlier appearance of certain motor activities, there is no evidence that the activities are performed qualitatively any better in practiced infants than in unpracticed infants. • Even when early gains are found, they do not seem to produce

an adult who is more proficient in motor skills.

Ethnic and Cultural Differences and Similarities in Reflexes

• Reflexes are:– Genetically determined– Universal – Cultural variations in ways displayed

• Example: Moro reflex - Some differences reflect cultural and ethnic variations • Caucasian infants show a pronounced response to situations that produce the

Moro reflex. Not only do they fling out their arms, but they also cry and respond in a generally agitated manner.

• Navajo babies react to the same situation much more calmly. Their arms do not flail out as much, and they cry only rarely.

• Serves as:– Diagnostic tool - Because reflexes emerge and disappear on a regular timetable,

their absence—or presence—at a given point of infancy can provide a clue that something may be amiss in an infant’s development.

– Social function– Survival function

Motor Development in Infancy

Milestones of Normal Motor Development

Motor Development in Infancy (cont.)

• When placed on their stomachs they wiggle their arms and legs and may try to lift their heavy heads.

• As their strength increases, they are able to push hard enough against the surface on which they are resting to propel their bodies in different directions.

• They often end up moving backwards rather than forwards, but by the age of 6 months they become rather accomplished at moving themselves in particular directions.

• These initial efforts are the forerunners of crawling, in which babies coordinate the motions of their arms and legs and propel themselves forward.

• Crawling appears typically between 8 and 10 months.

• Walking comes around the age of 9 months; most infants are able to walk by supporting themselves on furniture, and half of all infants can walk well by the end of their first year of life.

• Most are able to sit without support by the age of 6 months.

Motor Development in Infancy

Fine Motor Skills

Motor Development in Infancy – Fine Motor Skills

• By the age of 3 months, infants show some ability to coordinate the movements of their limbs.

• Although infants are born with a rudimentary ability to reach toward an object, this ability is neither very sophisticated nor very accurate.

• It disappears around the age of 4 weeks.•

• A different, more precise, form of reaching reappears at 4 months. It takes some time for infants to coordinate successful grasping after they reach out, but in fairly short order they are able to reach out and hold onto an object of interest.

• By the age of 11 months, infants are able to pick up off the ground objects as small as marbles—something caregivers need to be concerned about, since the next place such objects often go is the mouth.

• By the time they are 2 years old, children can carefully hold a cup, bring it to their lips, and take a drink without spilling a drop.

• Grasping, like other motor advances, follows a sequential developmental pattern in which simple skills are combined into more sophisticated ones.

Developmental Norms

Comparing Individual to Group Norms:– Represent the average performance of a large sample of

children of a given age. – Permit comparisons between a particular child’s performance on

a particular behavior and the average performance of the children in the norm sample.

– Must be interpreted with caution! All babies vary!

• Brazelton Neonatal Behavior Assessment Scale (NBAS) -one of the most widely used techniques to determine infants’ normative standing; measure designed to determine infants’ neurological and behavioral responses to their environment; provides a supplement to the traditional Apgar test.

Nutrition in Infancy

• Without proper nutrition, infants cannot reach physical potential and may suffer cognitive and social consequences

• Infants differ in growth rates, body composition, metabolism, and activity levels

• Rapid physical growth that occurs during infancy is fueled by the nutrients that infants receive. Without proper nutrition, infants cannot reach their physical potential, and they may suffer cognitive and social consequences.

Nutrition in Infancy (cont.)

• About 50 calories per day for each pound of weight

• Most infants regulate their caloric intake quite effectively on their own

• Most Important!!!!! If are allowed consume as much they seem to want, and not pressured to eat more, they will be healthy

Malnutrition• Children living in many developing countries • Slower growth rate • Chronically malnourished during infancy = later lower IQ score• Malnutrition, the condition of having an improper amount and

balance of nutrients, produces several results, none good. • More common among children living in many developing

countries • Slower growth rate apparent by the age 6 months• By 2 years, height and weight are only 95 percent the height

and weight of children in more industrialized countries.• Chronically malnourished during infancy later score lower on

IQ tests and tend to do less well in school. These effects may linger even after diet has improved substantially.

United States and Malnutrition

In the United States, some 12 million children live in poverty, which puts them at risk for malnutrition. In fact, although overall poverty rates are no worse than they were 20 years ago, the poverty rate for children under the age of 3 has increased. Some one-quarter of families who have children 2 years old and younger live in poverty.

When Malnutrition Is Severe

• Marasmus - a disease in which infants stop growing. Marasmus, attributable to a severe deficiency in proteins and calories, causes the body to waste away and ultimately results in death.

• Kwashiorkor - Older children are susceptible to kwashiorkor, a disease in which a child’s stomach, limbs, and face swell with water.

Nonorganic Failure to Thrive

• Infants receive sufficient nutrition but are deprived of attention and stimulation.

• Symptoms include underdevelopment, listlessness, and apathy and usually occurs by age 18 months.

• Reversal possible through intensive parent training or removal to emotionally supportive environment.

Infants and Obesity

• There is no clear correlation between obesity during infancy and obesity at the age of 16 years, some research suggests that overfeeding during infancy may lead to the creation of an excess of fat cells, which remain in the body throughout life and may predispose a person to be overweight.

• Also, weight gain during infancy is associated with weight at age 6 and weight at age 6 is associated with adult obesity.

Breast-feeding

• Starting around the 1940s, the general belief among child care experts was that breast-feeding was an obsolete method that put children unnecessarily at risk.• Bottle-feeding argument: parents could keep track of

amount of milk their baby was receiving and could ensure that child was taking in sufficient nutrients. Use of the bottle was also supposed to help mothers keep their feedings to rigid schedule of one bottle every 4 hours, the recommended procedure at that time.

• Mothers who breast-fed their babies could never be certain just how much milk their infants were getting.

Breast-feeding (cont.)• Breast-feeding argument: For first 12 months of life, there is no

better food for an infant than breast milk.• Breast milk not only contains all the nutrients necessary for growth,

but it also seems to offer some degree of immunity to a variety of childhood diseases, such as respiratory illnesses, ear infections, diarrhea, and allergies.

• Breast milk is more easily digested than cow’s milk or formula, and it is sterile, warm, and convenient for the mother to dispense.

• There is even some evidence that breast milk may enhance cognitive growth, leading to high adult intelligence. Babies are more responsive to touch.

• For mother, may have lower rates of ovarian cancer and breast cancer prior to menopause. Hormones produced during breast-feeding help shrink uteruses of women following birth, enabling their bodies to return more quickly to a prepregnancy state. Hormones also may inhibit ovulation, reducing (but not eliminating!) chance of becoming pregnant, and thereby helping to space birth of additional children.

Conclusion – Breast is Best!

Introducing Solid Foods

• Solids can be started at 6 months but are not needed until 9 to 12 months (AAFP)– Introduced gradually, one at a time– Can be canned baby food or made at home– Order to give foods – remember one at a time to

determine if allergies exist:• Cereal • strained and pureed fruits • strained or pureed vegetables• strained or pureed meats• Small bits of table food after age 1• No cow’s milk until after age 1

Visual Perception of Infants

• Newborn’s distance vision ranges from 20/200 to 20/600

• By 6 months, average infant’s vision is already 20/20

• Other visual abilities grow rapidly– Binocular vision– Depth perception– Infant can only see with accuracy visual material up to

20 feet that an adult with normal vision is able to see with similar accuracy from a distance of between 200 and 600 feet. ; distance vision is 1/10th to 1/3rd that of average adult’s.

Infant Visual Preference

• Preferences that are present from birth– Genetically

preprogrammed to prefer particular kinds of stimuli

– Prefer to look at patterned over simpler stimuli

Infant Visual Preference (cont.)

• They prefer curved over straight lines, three-dimensional figures to two-dimensional ones, and human faces to non-faces. Such capabilities may be a reflection of the existence of highly specialized cells in the brain that react to stimuli of a particular pattern, orientation, shape, and direction of movement.

• Prefer their own mother’s face to other faces; distinguish between male and female faces

Auditory Perception of Infants

• Infants – Hear before birth and have good auditory

perception after they are born– Are more sensitive to certain frequencies– Reach adult accuracy in sound localization by

age 1– Can discriminate groups of different sounds– React to changes in musical key and rhythm– Can discriminate many language related

sounds

Smell and Taste in Infants

• Smell– Well developed at birth– Helps in recognition of mother early in life

• Taste– Have innate sweet tooth– Show facial disgust at bitter taste– Develop preferences based on what mother

ate during pregnancy

The Power of Touch

• Touch is one of most highly developed sensory systems in a newborn

• Even youngest infants respond to gentle touches

• Several of the basic reflexes present at birth require touch sensitivity to operate

• Several theorists have suggested that one of the ways children gain information about the world is through touching.

Multimodal Perception

• New area of study in infant research:– considers how information that is collected by

various individual sensory systems is integrated and coordinated.

• Some researchers argue that sensations are initially integrated with one another in the infant

• Others maintain that infant’s sensory systems are initially separate and that brain development leads to increasing integration

Baby Einstein programs

• Does an unusually high level of stimulation during sensitive periods produce developmental gains beyond what a more commonplace level of stimulation would provide? – No!

• Attempts to accelerate physical and sensory-perceptual development yield little success

»Yet • Infants need sufficient physical and sensory

stimulation

How can this be accomplished?• Carry a baby in different positions—in a backpack, in a frontpack, or

in a football hold with the infant’s head in the palm of your hand and its feet lying on your arm. This lets the infant view the world from several perspectives.

• Let infants explore their environment - . Don’t contain them too long in a barren environment. Let them crawl or wander around—after first making the environment “childproof” by removing dangerous objects.

• Engage in “rough-and-tumble” play - Wrestling, dancing, and rolling around on the floor—if not violent—are activities that are fun and that stimulate older infants’ motor and sensory systems.

• Let babies touch their food and even play with it - Infancy is too early to start teaching table manners.

• Provide toys that stimulate the senses, particularly toys that can stimulate more than one sense at a time. For example, brightly colored, textured toys with movable parts are enjoyable and help sharpen infants’ senses.