CHAPTER 4
PHYSICAL, SENSORY, AND PERCEPTUAL
DEVELOPMENT IN INFANCY
RESOURCES-AT-A-GLANCE
Detailed Outline
Learning
Objectives
Instructor’s Resources
Test Bank
MyPsychLab Connections
Chapter Introduction pp. 82–83
PowerPoint Slides
1-4
Sketchnote Videos
Birth and the Newborn
Infancy
Physical Changes pp. 83–89
The Brain and the Nervous System
Reflexes and Behavioral States
4.1
4.2
Lecture Enhancer
Why Do Primitive Reflexes
Disappear?
5-23
MC 1-37
FI 76–82
SA 91–96
Watch
The Newborn’s Reflexes, p. 85
Motor Development in Infants
Infancy: Infant Fine Motor
Development across Cultures,
p. 87
Toddlerhood: Gross Motor
Development across Cultures,
p. 87
Malnutrition
Health Care and Immunizations
Health and Wellness pp. 89-91
Nutrition
4.4
PowerPoint Slides
24–34
MC 38-48
SA 97–99
Watch
Birth and the Newborn:
Sensory Skills pp. 95–97
Vision
Hearing and Other Senses
4.9
4.10
Lecture Enhancer
The Competent Newborn
PowerPoint Slides
36–38
MC 54-61
FI 86–87
SA 102-103
Explaining Perceptual Development
4.13
ES 110–111
Perceptual Skills pp. 97–102
Studying Perceptual Development
4.11
Lecture Enhancer
Assessing Infant Perceptual
MC 62-75
FI 88–90
Watch
Infancy: Habituation, p. 97
CHAPTER PREVIEW
During the first 2 years after birth, infants go from being relatively unskilled newborns to toddlers who
can move about efficiently, formulate goals and plans, and use words. There are also many important
variations across individuals and groups.
as the bones, the muscles, the lungs, and the heart.
Babies depend on the adults in their environments to help them stay healthy. They need the right foods in
the right amounts. Malnutrition in infancy can seriously impair a baby’s brain because the nervous
The preference technique, habituation, and dishabituation are used to study perceptual development.
Depth perception is present in at least rudimentary form by 3 months. The “looking” strategies of
newborns seem to be focused on locating objects; after about 2 months, their focus changes to identifying
LEARNING OBJECTIVE QUESTIONS
After completing Chapter 4, students should be able to answer the following questions:
4.1 What important changes in the brain take place during infancy?
4.2 How do infants’ reflexes and behavioral states change?
4.3 How do infants’ bodies change, and what is the typical pattern of motor skills development in the
first 2 years?
4.4 What are the nutritional needs of infants?
4.5 How does malnutrition affect infants’ development?
4.6 What are infants’ health-care and immunization needs?
4.7 What have researchers learned about sudden infant death syndrome?
4.8 How do infant mortality rates vary across groups?
4.9 How do infants’ visual abilities change across the first months of life?
4.10 How do infants’ senses of hearing, smell, taste, touch, and motion compare to those of older
children and adults?
KEY TERMS
intermodal perception (p. 100)
sudden infant death syndrome
myelinization (p. 85)
(SIDS) (p. 92)
nativists (p. 101)
synapses (p. 83)
plasticity (p. 84)
synaptogenesis (p. 83)
preference technique (p. 97)
tracking (p. 95)
primitive reflexes (p. 85)
visual acuity (p. 95)
pruning (p. 83)
reticular formation (p. 85)
INTEGRATED CHAPTER TEACHING NOTES
PHYSICAL CHANGES (pp. 83-89)
MyPsychLab Connections
Watch: The Newborn’s Reflexes, p. 85
Watch: Motor Development in Infants and Toddlers: Karen Adolph, p. 86
Watch: Infancy: Infant Fine More Development across Cultures, p. 87
Watch: Toddlerhood: Gross Motor Development across Cultures, p. 87
Discussion Launcher (Learning Objective 4.1, p. 83)
Predict what would happen if the brain was not developing faster than the rest of an infants’ body.
The Brain and the Nervous System
LO 4.1 What important changes in the brain take place during infancy?
At birth, the midbrain and the medulla are the most fully developed structures of the brain. These two
parts, both in the lower area of the skull and connected to the spinal cord, regulate vital functions such as
Discussion Launcher (Learning Objective 4.1, p. 83)
What do you think would happen if the cortex was well-developed at birth and the midbrain and medulla
were not well-developed?
Synaptic Development
All these brain structures are composed of two basic types of cells: neurons and glial cells. Virtually all
of both types of cells are already present at birth. The developmental process after birth primarily
during those years.
Discussion Launcher (Learning Objective 4.1, p. 83)
If a child is born with fewer neurons and glial cells than normal, what might be the long-range prognosis?
Brain development is not entirely smooth and continuous. An initial burst of synapse formation in the
first year or so after birth is followed by a pruning of synapses in each area of the brain, as redundant
pathways and connections are eliminated and the “wiring diagram” is cleaned up.
This cycle of synaptogenesis followed by pruning continues through the lifespan. With each cycle, the
brain becomes more efficient. Consequently, a 1-year-old actually has a denser set of dendrites and
There are several important implications from the cyclical, synaptogenesis-pruning feature of
neurological development:
▪ Brain development follows the old dictum: Use it or lose it. A child growing up in a rich or
intellectually-challenging environment will retain a more complex network of synapses than one
growing up with fewer forms of stimulation.
▪ The brain changes significantly throughout the entire human lifespan. New information about the
Discussion Launcher (Learning Objective 4.1, pp. 83-85)
Someone might argue that programs like Head Start—designed to alleviate the negative effects of
poverty—begin too late. Perhaps we ought to aim any supplementary stimulation programs at infants.
What do you think?
Feature Box Activity (Learning Objective 4.1, p. 84)
No Easy Answers: TV for Tots: How Much Is Too Much?
What are some ethical implications to conducting an experiment to see if television watching causes
ADHD?
Myelinization
Another crucial process in neuronal development is the creation of sheath, or coverings, around individual
axons, which electrically insulate them from one another and improve the conductivity of the nerve.
These sheaths are made of a substance called myelin; the process of developing the sheath is called
myelinization.
The sequence of myelinization follows both cephalocaudal and proximodistal patterns. For example,
nerves serving muscle cells in the hands are myelinized earlier than those serving the feet. Myelinization
Discussion Launcher (Learning Objective 4.1, p. 85)
What might happen if myelinization did not occur?
Reflexes and Behavioral States
LO 4.2 How do infants’ reflexes and behavioral states change?
Discussion Launcher (Learning Objective 4.2, p. 85)
Why do you suppose that changes, or the lack of these changes, may indicate nervous system health?
Reflexes
Neonates have many adaptive reflexes that help them survive. Some, such as automatically sucking any
object that enters the mouth, disappear in infancy or childhood. Others protect us against harmful stimuli
Discussion Launcher (Learning Objective 4.2, p. 85)
What would be different about development, and about adult–baby interactions, if babies were born
without any reflexes, but instead had to learn every behavior?
Behavioral States
Researchers have described five different states of sleep and wakefulness in neonates, referred to as states
of consciousness. Most infants move through these states in the same sequence: from deep sleep to
lighter sleep to fussing and hunger and then to alert wakefulness. After they are fed, they become drowsy
and drop back into deep sleep. The cycle repeats itself about every two hours. Neonates sleep as much as
Cross-cultural studies suggest that crying increases in frequency over the first 6 weeks, and then tapers
off. Fifteen to twenty percent of infants develop colic, a pattern involving intense bouts of crying totaling
LO 4.3 How do infants’ bodies change, and what is the typical pattern of motor skills development in the
first 2 years?
Half of all the growth in a person’s life is completed by age 2. Additionally, there are many qualitative
changes, such as those that involve motor skills, that also happen during this period.
Growth and Motor Skills
Babies grow ten to twelve inches and triple their body weight in the first year. At about age 2 for girls
and age 2-and-a-half for boys, toddlers are half as tall as they will be as adults. A person’s adult height
can be reliably predicted by doubling his or her height at age 2 to 2-and-a-half. Two-year-olds have
proportionately much larger heads than do adults—obviously needed to hold their nearly full-sized brains.
Discussion Launcher (Learning Objective 4.3, pp. 86-87)
Predict the result if babies continued to grow throughout childhood at the same rate they grow during the
first year. (Think deeper than just size; include what you know about the cephalocaudal and
proximodistal principles of development.)
Explaining Motor Skill Development
Throughout infancy, girls are ahead of boys in some aspects of physical maturity. Female infants may
Discussion Launcher (Learning Objective 4.3, p. 87)
How might these gender differences influence how caregivers interact with infants?
Despite gender differences in the rate of physical development, the sequence of motor skills development
is virtually the same for all children, even those with serious physical or mental handicaps. Children with
an intellectual disability move through the various motor milestones more slowly than normal children,
influence development, including inborn genetic factors and environmental variables such as the
availability of adequate nutrition.
Discussion Launcher (Learning Objective 4.3, p. 87)
What other factors might interact to affect the inborn timetable for motor skill development?
Research supports the notion that experience influences motor development. Opportunities to practice
motor skills seem to be particularly important for young children who have disorders, such as cerebral
Discussion Launcher (Learning Objective 4.3, pp. 87-88)
How might the information about practicing motor skills affect our behavior as caregivers?
Developing Body Systems
During infancy, bones change in size, number, and composition. Changes in the number and density of
bones in particular parts of the body are responsible for improvements in coordinated movement, such as
Discussion Launcher (Learning Objective 4.3, p. 88)
Why do you suppose an infant’s bones are softer than an adult’s?
Muscle fibers are virtually all present at birth although they are initially small and watery and contain a
fairly high proportion of fat. Changes in muscle composition lead to increases in strength that enable 1-
year-olds to walk, run, climb, and so on.
Critical Thinking Questions (Learning Objectives 4.1-4.3, pp. 83-89)
Animal research plays a prominent role in developmentalists’ understanding of early physical
development. What are the problems with generalizing from the results of laboratory studies of animals
to infants who are developing in the real world?
HEALTH AND WELLNESS (pp. 89-91)
MyPsychLab Connections
Watch: Birth and the Newborn: Breastfeeding Practices across Cultures, p. 89
Nutrition
LO 4.4 What are the nutritional needs of infants?
Breastfeeding is substantially superior nutritionally to bottle-feeding. Breast milk provides important
Discussion Launcher (Learning Objective 4.4, p. 89)
What specific changes in policies or practices do you think would increase the rate of breastfeeding in
your country?
Malnutrition
LO 4.5 How does malnutrition affect infants’ development?
Malnutrition in infancy can seriously impair an infant’s brain because the nervous system is the most
rapidly developing body system during the first 2 years.
▪ Macronutrient malnutrition results from a diet that contains too few calories. It is the leading cause of
death of children under the age of 5.
▪ When the calorie deficit is severe, a disease called marasmus results. Infants with marasmus weigh
less than 60 percent of the weight expected for their age, and many suffer permanent neurological
Discussion Launcher (Learning Objective 4.5, p. 90)
It is clear that nutrition in infancy is essential to the health and development of children. Malnutrition,
however, still exists even in industrialized countries. In small groups, identify policies and procedures
that could be implemented to increase the nutrition of infants. What long-range economic benefits could
result?
Health Care and Immunizations
LO 4.6 What are infants’ health-care and immunization needs?
Infants need frequent medical check-ups. While much of well-baby care may seem routine, it is
Discussion Launcher (Learning Objective 4.6, p. 90)
Why is slow motor development a possible indicator of an intellectual disability?
One of the most important features of well-baby care is the opportunity it provides for the vaccination of
the infant against a variety of diseases. Although immunizations later in childhood provide good
protection against these diseases, the evidence suggests that immunization is most effective when it
Discussion Launcher (Learning Objective 4.6, pp. 90-91)
Formulate an idea about how an infant’s suffering a series of ear infections might affect the social
environment that supports language development. Do you think it’s possible for ear infections in infancy
to affect language development for social, as well as neurological, reasons?
A full set of immunizations includes vaccination for the following:
▪ Three of hepatitis vaccine
▪ Four of diphtheria/tetanus/pertussis
Critical Thinking Question (Learning Objectives 4.4-4.6, pp. 89-91)
INFANT MORTALITY (pp. 91-95)
Researchers define infant mortality as death within the first year after birth. The rate has been declining
Sudden Infant Death Syndrome
LO 4.7 What have researchers learned about sudden infant death syndrome?
Sudden infant death syndrome (SIDS), in which an apparently healthy infant dies suddenly and
unexpectedly, is the leading cause of death between 1 month and 1 year of age. Physicians have not yet
uncovered the basic cause of SIDS, but there are a few clues:
▪ It is more common in the winter when babies may be suffering from viral infections that cause
breathing difficulties.
brains often show signs of delayed myelinization.
Feature Box Activity (Learning Objective 4.7, p. 92)
Developmental Science in the Clinic: When an Infant Dies
Speculate as to the implications of babies looking at their “attractive” or “unattractive” caregivers.
Group Differences in Infant Mortality
LO 4.8 How do infant mortality rates vary across groups?
Infant mortality rates, including deaths attributable to both congenital abnormalities and to SIDS, vary
widely across racial groups in the United States.
▪ Asian American babies: about 5 per 1,000
▪ Hispanic babies (Mexican American, Cuban American, and South and Central American): 5.4 per
1,000
▪ White babies: about 5.9 per 1,000
Discussion Launcher (Learning Objective 4.7, pp. 93-94)
List possible factors that could influence the link between poverty and infant mortality.
Mortality rates among babies of immigrants of all groups are lower than those of U.S.-born infants.
These findings challenge the poverty explanation for group differences in infant mortality because
Critical Thinking Question (Learning Objectives 4.7-4.8. pp. 91-95)
Generate your own hypothesis to explain group differences in infant mortality. What kind of information
would you need to test your hypothesis?
SENSORY SKILLS (pp. 95-97)
Vision
LO 4.9 How do infants’ visual abilities change across the first months of life?
Visual acuity is the ability to see details from various distances. It is fairly poor in newborns compared to
that of adults, but it improves rapidly during the first year as a result of synaptogenesis, pruning, and
myelinization in the neurons that serve the eyes and the brain’s vision processing centers. Most children
reach the level of 20/20 vision by about 2 years of age. It is difficult to determine an infant’s true visual
Hearing and Other Senses
LO 4.10 How do infants’ senses of hearing, smell, taste, touch, and motion compare to those of
older children and adults?
Hearing
Although children’s hearing improves up to adolescence, newborns’ auditory acuity is actually better
than their visual acuity. Within the general range of pitch and loudness of the human voice, newborns
Smelling and Tasting
Smelling and tasting are intricately related. Taste is detected by the taste buds on the tongue, which
register four basic tastes: sweet, sour, bitter, and salty. Newborns appear to respond differently to all four
of the basic flavors.
Critical Thinking Question (Learning Objectives 4.9-4.10, pp. 95-97)
In what ways do babies’ sensory skills contribute to the development of parent-infant relationships?
PERCEPTUAL SKILLS (pp. 97-102)
MyPsychLab Connections
Watch: Infancy: Habituation, p. 97
Simulate: The visual cliff, p. 98
Studying Perceptual Development
LO 4.11 How do researchers study perceptual development?
Researchers use three basic methods that allow us to “ask” a baby about what he experiences.
▪ In the preference technique, the baby is simply shown two pictures or two objects, and the researcher
keeps track of how long the baby looks at each one.
▪ Habituation is the process of getting used to a stimulus. Its opposite is dishabituation, learning to
Discussion Launcher (Learning Objective 4.11, p. 97)
List examples of how we “habituate” information on a daily basis.
Discussion Launcher (Learning Objective 4.11, p. 97)
Try to imagine a baby who is unable to habituate. What might be the consequences of such a lack?
Discussion Launcher (Learning Objective 4.11, p. 97)
Why is it important to researchers that habituation and dishabituation indicate “the same” or “different”?
Looking
LO 4.12 How do depth perception and patterns of looking change over the first 2 years?
Developmentalists believe that infants’ patterns of looking at objects tell us a great deal about what they
are trying to gain from visual information.
Depth Perception
One of the perceptual skills that has been most studied is depth perception. It is possible to judge depth
using any (or all) of three different kinds of information:
▪ Binocular cues involve both eyes, each of which receives a slightly different visual image of an
object. The closer the object is, the more different these two views. Information from the muscles of
Discussion Launcher (Learning Objective 4.12, p. 98-99)
Give examples of each type of depth perception.
What Babies Look At
In the first 2 months, a baby’s visual attention is a search for meaningful patterns. Babies scan the world
Feature Box Activity (Learning Objective 4.12, p. 99)
Research Report: Langlois’s Studies of Babies’ Preferences for Attractive Faces
Speculate as to the implications of babies looking at their “attractive” or “unattractive” caregivers.
Listening
LO 4.13 How do infants perceive human speech, recognize voices, and recognize sound patterns
other than speech?
One of the central questions has to do with how early a baby can make discriminations among different
speech sounds.
▪ As early as one month, babies can discriminate between speech sounds like pa and ba.
Discussion Launcher (Learning Objective 4.13, p. 100)
What would you say to a mother who believes that her premature infant is unresponsive to her because
the baby doesn’t appear to recognize her voice?
Combining Information from Several Senses
LO 4.14 What is intermodal perception?
Discussion Launcher (Learning Objective 4.14, pp. 100-101)
Explaining Perceptual Development
LO 4.15 What arguments do nativists and empiricists offer in support of their theories of
perceptual development?
The study of perceptual development has been significant because it has been a key battleground for the
dispute about nature versus nurture. Nativists claim that most perceptual abilities are inborn, while
empiricists argue that these skills are learned.
There are strong arguments for a nativist position on perceptual development. Researchers have found
that more and more skills are already present in newborns or very young infants.
▪ Good auditory acuity
▪ Poor but adequate visual acuity
Research with other species provides support for empiricism because some minimum level of experience
is necessary to support the development of the perceptual systems.
Discussion Launcher (Learning Objective 4.15, p. 101)
Discuss the ethical issues of conducting research on human infants’ perceptual development.
Discussion Launcher (Learning Objective 4.15, p. 101)
Make suggestions for ways to enhance the perceptual development of infants.
We can best understand the development of perceptual skills by thinking of it as the result of an
Critical Thinking Question (Learning Objectives 4.11-4.15, pp. 97-102)
In what ways do babies’ sensory skills contribute to the development of parent-infant relationships?
LECTURE ENHANCERS
Why Do Primitive Reflexes Disappear?
Reflexes exist to aid in the survival of the infant, but the primitive reflexes begin to disappear at about 6
months of age. An important question to consider is why would these primitive reflexes disappear if they
The Competent Newborn
Many individuals (especially those who do not have children of their own or who do not work closely
with children) have the impression that the newborn is at the mercy of its environment. Although
certainly the newborn cannot survive well on its own, it is ideally suited to respond to her environment.
From the moment the baby is born, she is ready to respond to the world, to make her needs known, and to
gather information from the environment to maximize survival. That is a pretty impressive list of abilities
for an infant brand new to the world. As developmental psychologists have learned more about newborns
and infants, they have come to understand how competent babies truly are.
Even the poor visual acuity of the newborn is ideally suited to its immediate needs. Newborns can see
most clearly those objects that are about eight inches away from their face. Given the way that newborns
are held, clothed, and fed, this distance is ideal. As the newborn gains more experience with focusing on
the environment, and especially as he or she develops the strength necessary for becoming mobile, visual
Hearing, however, is a different story. The unborn child can hear very well about 8 months after
conception. For at least a month prior to birth, then, he or she can have experiences with the voices of
individuals. It further illustrates the point that the child is born ideally suited to respond to the
environment.
Assessing Infant Perceptual Development
Researchers have not always understood the true competency of newborns and young infants. One of the
primary reasons for this lack of understanding was a lack of research methods that could be used with
young children. After all, you cannot simply ask a 2-month-old if she notices something. Fortunately for
us, however, researchers have utilized what we know about infants to develop research techniques that
Through the use of concepts, such as habituation and dishabituation, we can begin to document visual
preferences, level of interest, memory for objects, and other indicators of infant perceptual and cognitive
development. Habituation is defined as an automatic reduction in the strength or vigor of a response to a
repeated stimulus. Why would an infant show a decreasing response to the same stimulus when it is
repeated? Because he is getting used to seeing it.
INSTRUCTOR RESOURCES
Media
▪ MyPsychLab—MyPsychLab contains a variety of engaging activities and assessments that aid in
teaching and learning, including the following tools:
o Writing Space. A single place to create, track, and grade writing assignments, provide writing
resources, and exchange meaningful, personalized feedback with students quickly and easily. For
Fall 2014 courses, Writing Space for the 7th edition will contain new auto-graded writing
▪ MyPsychLab Connections
o Watch: The Newborn’s Reflexes, p. 85
o Watch: Motor Development in Infants and Toddlers: Karen Adolph, p. 86
o Watch: Infancy: Infant Fine More Development across Cultures, p. 87
o Watch: Toddlerhood: Gross Motor Development across Cultures, p. 87