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Chapter 4
Physical
Development in
Infancy and
Toddlerhood
.
Body Growth
 Gain 50% in height from birth to age
1; 75% by age 2
 Grow in spurts
 Gain “baby fat” until about 9 months,
then get slimmer
 Girls slightly shorter and lighter than
boys, some ethnic differences
Growth Trends
Cephalocaudal
Proximodistal
 “Head to tail”
 Lower part of body
grows later than the
head
 “Near to far”
 Extremities grow
later than head,
chest, and trunk
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Growth
During
First Two
Years
Figure 5.1
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Epiphyses of the Bone
Figure 5.2
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The Skull at Birth
Figure 5.3
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Brain Development
 Human brain has 100 to 200
billion neurons that
store/transmit information
 At birth, brain closest to adult
size than any other physical
structure (@ 75%)
Figure 5.4
Major Milestones of
Brain Development
Figure 5.5
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Regions
of the
Cerebral
Cortex
Figure 5.8
Lateralization and Plasticity of
the Cerebral Cortex
Specialization of the left and right hemispheres of
the brain is called lateralization.

Left hemisphere: specializes in language; positive
emotion

Right hemisphere: non-speech sounds, negative
emotion; spatial
Highly plastic cerebral cortex, many areas are not
yet committed to one function
Brain Plasticity Insights
 Injuries to the cerebral cortex occurring before birth or in
the first 6 months, language delays persisted to about
3½ years of age.
 By age 5, the children caught up in grammatical and
vocabulary skills; undamaged area of the brain—either
hemisphere—take over the language function.
 Spatial skills showed more impairment after a brain
injury, likely because spatial processing is more
lateralized at birth.
 Brain plasticity can occur later in adulthood (e.g., in
stroke victims).
Brain Development in
Orphanage Children
Figure 5.9
Appropriate Stimulation
Experience-expectant growth
Experience-dependent growth

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.
Influences on Early Growth
Heredity
Nutrition
 Breast v. bottle feeding
 Malnutrition
Emotional well-being
 Problems can cause
failure to thrive
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Benefits of Breastfeeding
 Correct fat–protein balance
 Nutritionally complete
 Promotes healthy growth patterns
 Disease protection
 Better jaw and tooth development
 Ensures digestibility
 Easier transition to solid food
Emotional Well-Being
Affection is as vital as food for healthy physical
growth.
Non-organic failure to thrive: weight, height, and
head circumference are substantially below agerelated growth norms.




Infants are withdrawn and apathetic.
Often a result of disturbed parent–child relationship
Unhappy marriage or parental psychological
disturbance may be at fault.
May cause lasting cognitive and emotional difficulties
The Sequence of
Motor Development
Gross-motor development

Crawling, standing,
walking
Fine-motor development

Reaching and grasping
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Gross- and Fine-Motor Development in the
First Two Years
Motor Skills as Dynamic Systems
Increasingly complex
systems of action with
each skill
Four factors in each new
skill:
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Cultural Variations in
Motor Development
Home environments and infant rearing
practices affect motor development.

Some cultures discourage rapid motor
progress.

Kipsigis of Kenya and the West Indians of
Jamaica teach early motor skills.

Western parents consider crawling and
“tummy time” essential, but not all cultures do.
Milestones of Reaching
Figure 5.14
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The Steps of
Classical Conditioning
Figure 5.10
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Operant Conditioning Terms
Reinforcer
Punishment
Increases probability Reduces probability
of behavior
of behavior
occurring again
occurring again
 Presenting
 Presenting desirable
unpleasant stimulus
stimulus
 Removing desirable
 Removing unpleasant
stimulus
stimulus
Using Habituation
to Study Infants
Figure 5.11
Imitation
 Imitation is a powerful method of learning.
 It is more difficult to induce in babies 2 to 3
months old than right after birth.
 Andrew Meltzoff: Newborns imitate as much as
older children and adults.
 Mirror neurons enable us to observe another
person’s behavior while simulating that
behavior in our own brain.
 Meltzoff’s theory of newborn imitation as a
voluntary capacity is controversial.
Imitation by
Human and
Chimpanzee
Newborns
Figure 5.12
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Developments in Hearing
p. 140 starts
4–7 months Sense of musical phrasing
“Screen out” sounds from non-native
6–8 months languages
7–9 months
Divide the speech stream into wordlike units
10 months
Can detect words that start with
weak syllables
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Improvements in Vision
Brain development helps
infants reach adult
levels of vision skills.
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2–4 months:
focus and color vision
6 months:
acuity, scanning, and
tracking
6–7 months:
depth perception
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Steps in Pattern Perception
3 weeks
 Poor contrast sensitivity
 Prefer large simple patterns
 Can detect fine-grained detail
2 months
 Prefer complex patterns
 Can detect patterns even if
4 months
boundaries are not really present
12
months
 Can detect objects if two-thirds
of drawing is missing
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Appearance of Checkerboards to
Very Young Infants
Figure 5.17
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Subjective
Boundaries in
Visual Patterns
Figure 5.18
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Early Face
Perception
Figure 5.19
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Testing Infants’ Ability to
Perceive Object Unity
Figure 5.20
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Acting on the Environment
Plays a Major Role in
Perceptual Differentiation
Figure 5.21
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