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Chapter 5
Physical Development in Infancy
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Learning Objectives
Key Terms and Concepts
Chapter Outline
Lecture Suggestions
Sudden Infant Death Syndrome (SIDS)
Infant Brain Growth
Class Activities
Supplemental Reading List
Prentice Hall PowerPoint slides available online
Multimedia Ideas
Handouts
LEARNING OBJECTIVES
After reading Chapter 5, students will know
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Understand how growth occurs in infancy.
Describe the development of the nervous system and its components.
Explain how brain development is susceptible to environmental influences.
Define a sensitive period.
Describe how neonates integrate their bodily systems. Explain the importance of sleep to infants.
Describe reflexes and understand why they are important.
Understand the development of motor skills in infancy.
Explain the concept of developmental norms, how they are determined, and their limitations.
Recognize the cultural dimensions of motor development.
Understand the effects of not having proper nutrition in infancy.
Explain the benefits of breast feeding.
Understand the processes that underlie infants’ understanding of the world around them.
Describe visual perception in infancy.
Describe auditory perception in infancy.
Understand infants’ sense of taste and smell and sensitivity to pain and touch.
Define the multimodal approach to perception.
Describe how parents can ensure that their infants receive sufficient physical and sensory stimulation.
KEY TERMS AND CONCEPTS
cephalocaudal principle
proximodistal principle
principle of hierarchical integration
principle of the independence of systems
neuron
synapse
myelin
cerebral cortex
plasticity
sensitive period
rhythms
state
rapid eye movement (REM) sleep
sudden infant death syndrome (SIDS)
reflexes
norms
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multimodal approach to perception
Brazelton Neonatal Behavioral
Assessment Scale (NBAS)
marasmus
kwashiorkor
nonorganic failure to thrive
sensation
perception
CHAPTER OUTLINE
I.
Physical Growth: The Rapid Advances of Infancy
A. Over the first two years of infancy, growth occurs at a rapid pace.
1. By age 5 months, the average infant’s birthweight has doubled to about
15 pounds.
2. By age 1, the infants’ birthweight has tripled to approximately 22 pounds.
3. By the end of its second year, the average child weighs four times its
birthweight.
4. By age 1, the average baby stands 30 inches tall.
5. By the end of the second year the average child is 3 feet tall.
B. Not all parts of the body grow at the same rate.
1. The Cephalocaudal Principle states that growth follows a pattern that begins
with the head and upper body pans and then proceeds to the rest of the body.
2. The Proximodistal Principle states that development proceeds from the center
of the body outward.
3. The Principle of Hierarchical Integration states that simple skills typically
develop separately and independently but are later integrated into more complex
skills.
4. The Principle of Independence of Systems suggests that different body systems
grow at different rates.
C. The nervous system comprises the brain and the nerves that extend throughout the body.
1. Infants are born with between 100 and 200 billion Neurons, the nerve cells of
the body.
2. Neurons communicate with other cells by means of fibers called dendrites at
one end that receive messages and a long extension at the other end known as an
axon that carries messages destined for other neurons.
3. Neurons do not touch one another, but they communicate by means of chemical
messengers, neurotransmitters, that travel across the gaps between neurons
known as Synapses.
4. Babies are born with more neurons than they need; as the infant’s experience in
the world increases, synaptic pruning occurs in which neurons that do not
become interconnected die off.
5. Neurons increase in size. They become coated with Myelin, a fatty substance
that insulates neurons and speeds the transmission of nerve impulses.
a. The brain triples its weight in the first 2 years of life.
b. The infant’s brain is 3/4 its adult size by age 2.
c. As they grow, neurons become arranged by function.
(1) Some move into the Cerebral Cortex, the outer layer of the brain.
(2) Others move to subcortical levels (breathing and heart rate), which
are below the cerebral cortex.
6. Plasticity is the degree to which a developing structure (e.g., the brain) or
behavior is susceptible to experience and is relatively great for the brain.
a. Infants who grow up in severely restricted environments are likely to
show differences in brain structure and weight.
b. Research with non-humans reveals that a Sensitive Period exists which
is a specific but limited time span, usually early in an organism’s life,
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II.
during which the organism is particularly susceptible to environmental
influences relating to some particular facet of development.
c. Compared with those brought up in more enriched environments,
infants raised in severely restricted settings are likely to show
differences in brain structure and weight
D. Behavior becomes integrated through the development of various body Rhythms, which
are repetitive, cyclical patterns of behavior.
1. An infant’s State is the degree of awareness it displays to both internal and
external stimulation. States include various levels of alertness, fussiness, and
sleepiness. Newborns may go through periods in which they jerk their legs in a
regular pattern every minute or so. Although some of these rhythms are apparent
just after birth, others emerge slowly over the first year as the neurons of the
nervous system become increasingly integrated.
2. Changes are reflected in brain waves measured by a device called an EEG
(electroencephalogram).
3. Infants spend the majority of time in the state of sleep.
a. On average, newborns sleep 16–17 hours daily, ranging from
10–20 hours a day.
b. Sleep stages are fitful and “out of sync” during early infancy in that they
appear in spurts of around 2 hours.
c. By the end of the first year most infants are sleeping through the night.
d. Infants have a cycle of sleep similar to but different than REM (Rapid
Eye Movement) the period of sleep found in adults and children and is
associated with dreaming.
(1) Brain waves are different than the dreaming sleep of adults.
(2) This active REM-like sleep takes up half an infant’s sleep at first,
and declines to one third of total sleep time by 6 months of age.
(3) REM sleep in young infants is likely related to autostimulation, a
means for the brain to stimulate itself, rather than dreaming.
(4) Cultural practices affect the sleep patterns of infants.
e. Sudden Infant Death Syndrome (SIDS) is a disorder in which
seemingly healthy infants die in their sleep.
(1) 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. It is clear that infants don’t
smother or choke; they die a peaceful death, simply ceasing to
breathe.
(2) No cause found although seems to be interruption of normal
patterns of sleep.
(3) Boys, African Americans, and low-birthweight and low-Apgar
scorers, and babies whose mothers smoked during pregnancy are at
higher risk.
(4) No means of prevention has been found although incidence has
been dramatically reduced by having babies sleep on their backs.
Motor Development
A. Basic Reflexes, unlearned, organized, involuntary responses that occur automatically in
the presence of certain stimuli, represent behavior that has survival value for the infant.
1. Swimming reflex, eye blink reflex, Moro reflex (see table 5.3 in text).
2. Many reflexes represent behavior that has survival value.
3. Some reflexes stay throughout life; others disappear over time.
4. Some researchers believe reflexes stimulate the brain toward development.
5. Reflexes are genetically determined and universal and may be remnants from the
past.
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6.
B.
C.
D.
E.
Reflexes can serve as helpful diagnostic tools for pediatricians because they
appear and disappear on a regular timetable.
Gross Motor Skills
1. By 6 months infants can move by themselves.
2. Most can sit unsupported by 6 months.
3. Crawling appears between 8–10 months.
4. Infants can walk holding on to furniture by 9 months and most can walk alone by
1 year.
Fine Motor Skills
1. By 3 months infants can coordinate movements of limbs.
2. Infants can voluntarily reach out by 4 months, and grasp an object by
11 months.
3. By age 2, infants can drink from a cup without spilling.
4. As children get older, they use a pincer grasp, where thumb and index finger
meet to form a circle.
5. Ethnic and Cultural Differences and Similarities in Reflexes Although
reflexes are, by definition, genetically determined and universal throughout all
infants, there are actually some cultural variations in the ways they are displayed.
a. Caucasian infants show a pronounced response to situations that
produce the Moro reflex. Not only do they fling out their arms, but also
they cry and respond in a generally agitated manner. In contrast, Navajo
babies react to the same situation much more calmly. Their arms do not
flail out as much, and they cry only rarely.
It is important to keep in mind that developmental Norms are the average performance of
a large sample of individuals of a certain age and mask substantial individual differences.
1. Brazelton Neonatal Behavioral Assessment Scale (NBAS) is a measure used
to determine infants’ neurological and behavioral responses to their environment.
a. Supplements the Apgar
b. 27 categories of responses
(1) Interactions with others
(2) Motor behavior
(3) Physiological control
(4) Response to stress
2. Norms should be based on large, heterogeneous samples.
3. The time at which specific motor skills appear is in part determined by cultural
factors.
4. There are certain genetic constraints on how early a skill can emerge.
5. Dynamic Systems Theory: How Motor Development Is Coordinated
a. describes how motor behaviors are assembled.
b. it is easy to think about motor development in terms of a series of
individual motoric achievements, the reality is that each of these skills
does not develop in a vacuum.
c. Each skill (such as a baby’s ability to pick up a spoon and guide it to
her lips) advances in the context of other motor abilities (such as the
ability to reach out and lift the spoon in the first place).
d. Furthermore, as motor skills are developing, so also are nonmotoric
skills such as visual capabilities.
Without proper nutrition, infants cannot reach their physical potential.
1. Malnutrition, the condition of having an improper amount and balance of
nutrients produces several results.
a. Slower growth
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b. Susceptibility to disease
c. Lower IQ scores
2. Risks are greater in underdeveloped countries and in areas with high
poverty rates.
3. Undernutrition is where there is some deficiency in the diet.
4. Malnutrition can cause Marasmus, a disease characterized by the cessation of
growth in infants.
5. Older children are susceptible to Kwashiorkor, a disease in which a child’s
stomach, limbs, and face swell with water.
6. Some children appear to be suffering from malnutrition even though they have
been receiving a sufficient supply of nutrients. These children may be suffering
from Nonorganic Failure to Thrive, which is due to a lack of stimulation,
attention, love, and emotional support.
7. Overfeeding during infancy may lead to unnecessary fat cells which remain in
the body throughout life.
a. It is not clear that an abundance of fat cells necessarily leads to adult
obesity, defined as weight greater than 20 percent above the national
average for a given height.
b. Genetic factors are an important determinant of obesity.
c. There appears to be no correlation between obesity during infancy and
obesity at the age of 16.
8. For the first 4 to 6 months of life there is no better food for an infant than
breast milk.
a. All essential nutrients
b. Natural immunity to childhood diseases
c. More easily digested
d. Health advantages for mother
e. May have emotional advantages for both mother and child
f. Only half of mothers in U.S. breastfeed
g. Factors influencing the decision to breastfeed include age, social status,
race, practical concerns, education, and health
9. Most babies can begin to eat solid foods at about 6 months, although solid foods
are not needed until 9 to 12 months of age.
a. Foods are introduced gradually.
b. Weaning, the cessation of breastfeeding, occurs on average in the U.S.
at 3–4 months.
c. Experts recommend infants be breastfed for the first 12 months.
The Development of the Senses
A. The processes that underlie infants’ understanding of the world around them are
Sensation, the stimulation of the sense organs, and Perception, the interpretation,
analysis, and integration of stimuli involving the sense organs and brain.
B. Visual Perception
1. Newborn infants cannot discern visual material beyond 20 feet.
2. By 6 months, the average infant’s vision is 20/20.
3. Binocular vision, the ability to combine both eyes’ vision to see depth and
motion is achieved at 14 weeks.
a. Gibson’s “visual cliff’ experiments showed that most infants between 614 months would not crawl over the apparent cliff.
b. We do not know how early this depth perception occurs in infancy.
4. Fantz’s research led to extensive investigations into infants’ visual preferences.
Infants:
a. Prefer to look at patterns and complex stimuli;
b. Prefer to look at faces;
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c. Show preferences for certain colors, shapes, and configurations;
d. Visual preferences are genetically influenced, but also learned.
C. Auditory Perception
1. The ability to hear begins prenatally.
2. Infants are more sensitive than adults to high and low frequencies but not to the
middle ranges.
3. Sound localization permits infants to discern direction from which a sound is
emanating.
a. This skill is poorer in infants than adults because of infants’ smaller
heads.
b. It reaches adult level at 1 year.
4. Infants can differentiate changes in melodies and sounds—a requirement for
language—and their mother’s voice from other voices.
D. Smell and Taste
1. Infants react to unpleasant tastes and smells from birth.
2. Some newborns can detect their mother’s smell, but only when breastfed.
3. Infants have an innate preference for sweets.
4. Infants develop taste preferences based on what their mothers drank while they
were in the womb.
E. Sensitivity to Pain and Touch
1. Infants are born with the capacity to feel pain.
2. Touch is one of the most highly developed sensory systems in a newborn.
a. The rooting reflex is strong.
b. Infants gain information about the world through touch.
c. Even the youngest infants respond to gentle touches and are calmed
by them.
F. Eventually infants use the Multimodal Approach to Perception in which information
collected by various individual sensory systems is integrated and coordinated.
LECTURE SUGGESTIONS
SUDDEN INFANT DEATH SYNDROME (SIDS) TEXTBOOK CD
The leading killer of infants is Sudden Infant Death Syndrome (SIDS), “accounting for about 16 percent of
the 38,000 babies born in the United States who die before their first birthday. . . Ninety percent of SIDS
deaths occur before 6 months of age, mostly between 2 and 4 months; rarely do such deaths occur beyond
12 months of age.” (McKenna, 1992). Interestingly, SIDS is not known to occur in any other species
besides humans and there is presently no known medical explanation for this heartbreaking event. Some
data are available. For example:
SIDS occurs most frequently in the winter
In the U.S., rates are highest among Native-Americans and poor African-Americans
Risk factors include teenage mothers, smoking during pregnancy, and premature birth
Possible causes include lack of breastfeeding, upper respiratory infections, respiratory
system collapse during sleep (McKenna, 1992)
Exposure to second hand tobacco smoke is a much bigger risk factor for SIDS than was
previously suspected (Arizona Republic)
An interesting phenomenon has occurred in the last few years. Pediatricians routinely advised parents to lay
their babies face down when they put them to sleep, to prevent the infants from choking in case they spit up.
Recently, doctors have been asking parents to lay their babies on their backs with the result that SIDS
deaths have dramatically decreased. British researchers have found that putting a baby on its side to sleep
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reduces the risk of SIDS but not as much as putting the baby on its back. McKenna suggests that modern
sleeping patterns may contribute to SIDS. By placing an infant in another room to sleep we force the baby
to “sleep too much—too long and too hard” and deprive the baby of “sensory intrusions” which wake the
infant up at crucial times in sleep stages.
Furthermore, “For every hour spent each day in a room where people smoke, the risk [of SIDS] increases
100 percent,” says Dr. Peter Fleming of the University of Bristol. Other risk factors include:
Lack of prenatal care
Low birthweight
Drug and alcohol abuse
Wrapping infants heavily or having loose bed clothes that can entangle the infant
Sources: Textbook CD
Arizona Republic (July 26, 1996). Tobacco smoke, infant death link confirmed. A9.
McKenna, J. J. (Winter, 1992). SIDS research. Mothering. pp. 45— 51.
National Sudden Infant Death Syndrome Clearinghouse
8201 Greenboro Drive, Suite 600
McLean, VA 22102
INFANT BRAIN GROWTH
When the human pelvis evolved thicker to adapt to walking in an upright position, the brain was also
evolving and getting larger. As a consequence, in order to pass through the birth canal, human infants must
be born early in their brain development. Although they are born with all the neurons (brain cells) they will
ever have—over 100 billion cells—their brain is only about 25 percent of its adult weight. By 24 months
the brain is about 75 percent of adult weight, which explains why babies and toddlers are so top heavy! All
of this brain growth is not new cells; in fact, many neurons die off as the brain specializes for language,
motor skills, etc. What grows are the axons and dendrites that connect neurons and the myelin that coats the
axons and speeds brain processing. Thus, a major portion of brain growth occurs outside the womb. (By
comparison, baby chimps are born with 50 percent of their adult brain weight.)
At birth, the lower brain (brain stem, cerebellum, limbic system) is more developed than those parts of the
brain allocated to thinking and reasoning (cerebrum). The lower brain helps the infant breathe, eat, sleep,
and controls all vital organs. The development of the “thinking” brain requires more dendrite connections
and myelin sheathing. This development requires a tremendous amount of sleep and nutrients. Is it any
wonder infants sleep so much and eat so frequently? Moreover, dendrite growth is stimulated as the infant is
exposed to a rich environment of sights and sounds and is allowed to move around. We know from studies
that severe malnutrition can cause inadequate brain growth and mental retardation. Studies with rats show
that those who grow up in a rich environment with lots of visual stimulation and movement have heavier
brains than rats who grow up in cages devoid of such a rich environment.
Source:
Ornstein, R., Thompson, R. F., & Macaulay, D. (1984). The Amazing Brain. Boston: Houghton Muffin.
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CLASS ACTIVITIES
CRITICAL THINKING EXERCISES
1.
2.
3.
4.
List the advantages and disadvantages of breastfeeding versus bottle feeding for mothers and for
infants.
Encourage class discussion and brainstorming about the evolutionary roots and roles of the various
infant reflexes.
Watch the segment titled “Nature’s Way” on the ABC News/Prentice Hall Video Library (see
Multimedia). This show offers views on the pros and cons of breastfeeding and should generate a
lively class discussion.
Have students work in groups discussing the following. Leave time for each group to share their
conclusions with the entire class.
a. How the sequence of motor activity associated with cephalocaudal and proximodistal
development are related to the infant’s abilities.
b. What abilities or situations might stimulate neural growth and/or “pruning down” in the infant.
c. What are the relationships between infant “states” and parental interactions and attachment.
d. How do you account for the amount of REM sleep infants need compared to the REM sleep of
later development? Do infants dream? Why or why not?
OTHER ACTIVITIES
Students can apply some of the concepts presented in Chapter 5 by observing infants outside the classroom.
You may choose to ask the students to write and share with the class their experiences on the following
“field trips”:
1.
A daycare center with infants
—students can observe physical development of various infants.
See Handout 5-1.
2. A toy store
—using Handout 5–2, have students determine how toys for infants enhance sensory development.
—if students have children or young brothers/sisters at home they can bring in toys that develop
the senses.
3. Pediatric Care Unit
—students visit a children’s ward of a hospital and report on what special skills are required of nurses
working with infants.
—report on infants with developmental delays.
SUPPLEMENTAL READING LIST
Corpus, J., Henderlong, E., & O’Donnell, A. (2005). A Live Demonstration To Enhance Interest And
Understanding In Child Development. Journal of Instructional Psychology, 32(1).
DiPietro, J., Caulfield, L., & Costigan, K. (2004). Fetal Neurobehavioral Development: A Tale of Two
Cities. Developmental Psychology, 40 (3), pp. 445-456.
Dixon, W. E. (2003). Twenty Studies that Revolutionized Child Psychology. Upper Saddle River, NJ:
Prentice Hall.
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Elkind, D. (1994). Ties That Stress: The New Family Imbalance. Cambridge, MA: Harvard University
Press.
Fadiman, J., & Frager, R. (2002). Personality: Personal Growth, 4th edition. New York: HarperCollins
College Publishers.
Gilligan, C. (1982). In a Different Voice: Psychological theory and women’s development. Cambridge,
MA: Harvard University Press.
Reis, H. T., Collins, W. A., & Berscheid, E. (2000). The Relationship Context of Human Behavior and
Development. Psychological Bulletin, 126 (6), pp. 844-872.
Siegel, D. J. (1999). The Developing Mind: How Relationships and the Brain Interact to Shape Who We
Are. New York: Guilford Press.
PowerPoints available for download on Web site for this textbook
MULTIMEDIA IDEAS
The Amazing Newborn (Polymorph Films, 1980, 25 minutes)
Developmental Phases Before and After Birth (Films for the Humanities and Sciences. 28 minutes)
This program examines the development of the fetus in utero and the child during the first year.
The First Year of Life (Films for the Humanities and Sciences, 28 minutes)
Examines newborn sensory and cognitive abilities and how they contribute to its interactions with
its environment and the development of individuality during the first year.
The Growing Infant (Insight Media, 1988, 30 minutes)
This video shows how infants develop physically. Includes a discussion of cephalocaudal and
proximodistal development.
Infancy: Landmarks of Development (Magna Systems, 1991)
Major landmarks in locomotion and fine motor skills are shown. Shows age norms and the
principles that affect physical growth and development.
Infancy and Early Childhood (Annenberg/PBS., 1990, 30 minutes)
Beginning with the first years of life, this video explores the early influences of the biological and
social clocks, how children develop, and how they gain confidence and curiosity.
The Mind: Development (Episode 2) (PBS., 1998, 60 minutes)
This video explores a wide range of topics including from cell division, through normal and
premature birth as well as a discussion of how brain maturation is intertwined with cognitive
maturation. Language, sound discrimination, and the sense of self are also included.
Mothers, Fathers, and Babies (Films for the Humanities and Sciences, 26 minutes)
This video observes the role of breastfeeding in different cultures and its effect on the role of
the father.
Nature’s Way (ABC News/Prentice Hall Video Library, 1995, 12:20 minutes)
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This segment of 20/20 discusses the pros and cons of breastfeeding. Some mothers who could not
breastfeed are interviewed.
Newborn (Filmmakers Library, 28 minutes)
Dr. T. Berry Brazelton discusses the newborn infant.
The Newborn (Films for the Humanities and Sciences, 23 minutes)
This video shows the reactions of the newborn 10 days after birth. The most important functions
such as sitting, standing, walking, grasping can already be recognized in their incipient form. The
first tests give the examining physician indications of possible damage to and developmental
disorders of the newborn.
Physical Growth & Motor Development (Concept Media, 19 minutes)
Right from Birth: The Wonders of the Brain (Insight Media, 2001, 15 minutes)
Details the physical development of a baby’s brain and explains how the stages of brain
development control and influence other areas of child development.
Right from Birth: The Many Worlds of Infancy (Insight Media, 2001, 15 minutes)
Looks at a child’s environment from a child’s point of view and discusses strategies for exploring a
child’s perspective.
Right from Birth: Discovering the World at Two to Three Months (Insight Media, 2001, 15 min)
Examines the 2-3 month development state when the infants investigate their surroundings with a
new curiosity.
INTERNET SITES
There are numerous medical journals available on the World Wide Web. You and your students can obtain
abstracts from medical journals and information on specific topics such as SIDS, infertility, low-birthweight
infants, etc.
American Medical Association Home Page
http://www.ama-assn.org
British Medical Journal
http://www.bmj.com/bmjpubs/sites.htm
The Multimedia Medical Reference Library
http://www.tiac.net/users/jtward/journals.html
The New England Journal Online
http://www.nejm.org
The National Institutes of Health Home Page
http://www.nih.gov
Global Network Navigator General Medical Information
http://www.com/gnn/wic/wics/med.general. html
HANDOUT 5–1
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Use this for a class assignment on infant motor activity.
HANDOUT 5–2
Use this for a class assignment on infant toys.
HANDOUT 5–3
Use this handout, or you can adapt it, for your students’ opportunity to reflect on their own infancy with
someone who knew them “when.”
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HANDOUT 5–1
Motor Development In Infancy
Observe several infants from newborns to 2 years old. Determine their levels of gross motor (lifting head, rolling
over, sitting up, crawling, cruising, walking alone, walking up stairs, running, etc.) and fine motor skills (reaching,
grabbing, picking up objects, feeding self, holding a cup, etc.).
Infant #1
sex
age
gross motor skills
fine motor skills
Infant #2
sex
age
gross motor skills
fine motor skills
Infant #3
sex
age
gross motor skills
fine motor skills
Infant #4
sex
age
gross motor skills
fine motor skills
Infant #5
sex
age
gross motor skills
fine motor skills
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HANDOUT 5–2
Infant Toy Survey
Examine several toys marketed for infants (see package age ranges). Determine how this toy is designed for infant
safety and to stimulate infant development, especially sensory development. Try to find one good toy and one
poor toy.
Toy #1
Description:
Recommended age range:
Toy rating (1 = poor, 2 = fair, 3 = average, 4 = good, 5 = excellent). Explain why.
durability
safety
attractiveness
source of stimulation
Toy #2
Description:
Recommended age range:
Toy rating:
durability
safety
attractiveness
source of stimulation
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HANDOUT 5–3
Reflective Journal Exercise #5
If possible, write about your own first year of life. (If this is not possible, you can write about your own children, or
interview another person about their first year.)
Where did you sleep? Describe your typical sleeping pattern during the first months (e.g., How many naps did you
take? When did you begin to sleep through the night?) Were you breastfed or bottlefed? Why? For how long? When
were you introduced to solid food? Were you allergic to any foods? Were you overweight, underweight, or average
weight at 1 year old? How old were you when you: rolled over, sat up, crawled, cruised, and walked alone? What
were some of your favorite toys? Why do you think this is so? (You might want to include some photos of yourself
from this period.)
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