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Infants and Children: Prenatal Through Middle Childhood

Eighth Edition

Chapter 5

Physical Development in Infancy and Toddlerhood

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Learning Objectives (1 of 2)

5.1 Discuss major changes in body size, muscle–fat make-up, body proportions, and variations in rate of physical growth over the first two years.

5.2 Describe brain development during infancy and toddlerhood, current methods of measuring brain functioning, and appropriate stimulation to support the brain’s potential.

5.3 How does organization of sleep and wakefulness change over the first two years?

5.4 Cite evidence indicating that heredity, nutrition, and parental affection contribute to early physical growth.

Learning Objectives (2 of 2)

5.5 Describe infant learning capacities, the conditions under which they occur, and the unique value of each.

5.6 Discuss the general course of motor development during the first two years, along with factors that influence it.

5.7 What changes in hearing and in depth, pattern, object, and intermodal perception take place during infancy?

5.8 Explain differentiation theory of perceptual development.

Body Growth

Typical gain in height is 50% by age 1, 75% by age 2.

“Baby fat” peaks at about 9 months.

Muscle tissue increases slowly, peaking in adolescence.

Physical Growth Trends

Cephalocaudal trend

“Head to tail”

Head develops more rapidly than lower part of the body.

Proximodistal trend

“Near to far”

Head, chest, and trunk grow ahead of extremities.

Differences in Growth

Girls are slightly smaller than boys, with higher ratio of fat to muscle.

Ethnic differences are apparent.

Skeletal age is the best estimate of physical maturity.

Brain Development

At birth, the brain is nearer to adult size than any other physical structure.

Human brain has 100 to 200 billion neurons that store/transmit information.

Synapses are tiny gaps between neurons.

Neurons send messages by releasing chemicals called neurotransmitters.

Major Milestones of Brain Development

Figure 5.3

(Based on Thompson & Nelson, 2001.)

Figure 5.3: Major milestones in brain development

Major Measures of Brain Functioning

Electroencephalogram (E E G)

Event-related potentials (E R Ps)

Functional magnetic resonance imaging (f M R I)

Positron emission tomography (P E T)

Near-infrared spectroscopy (N I Rs)

Regions of the Cerebral Cortex

Figure 5.6

Figure 5.6: The left side of the human brain, showing the cerebral cortex

Lateralization of the Cerebral Cortex

Lateralization: specialization of the two hemispheres

Left hemisphere

Better at sequential, analytic processing

Good approach for communicative information

Right hemisphere

Specialized for holistic, integrative processing

Good for spatial abilities and regulating negative emotion

Brain Plasticity

Brain plasticity: If part of the cerebral cortex is damaged, other parts can take over tasks it would have handled.

Brain is highly plastic during the first few years.

In one study, after early brain injury, language skills recovered by age 5; spatial skills were more impaired.

Despite recovery, a “crowding effect” hindered cognitive progress: Complex abilities suffered.

Plasticity can occur at later ages but is far more limited.

Sensitive Periods in Brain Development: Romanian Orphans

Children adopted before age 6 months displayed impressive cognitive catch-up.

Those adopted after 6 months showed serious intellectual deficits.

Factors:

Decreased activity in the cerebral cortex

Disruption of capacity to manage stress

Disrupted response to pleasurable social interaction

Influence of Age of Adoption on Mental Test Scores of British and Romanian Adoptees

Figure 5.7

(Adapted from Beckett et al., 2006.)

Figure 5.7: Relationship of age at adoption to mental test scores at ages 6 and 11 among British and Romanian adoptees

Appropriate Stimulation

Experience-expectant brain growth

Depends on ordinary experiences “expected” by brain for normal growth

Occurs early and naturally

Experience-dependent brain growth

Results from specific learning experiences

Varies widely across individuals and cultures

Rushing early learning overwhelms the brain’s neural circuits.

Sleep and Wakefulness

Organization of sleep and wakefulness changes as a result of

brain development.

cultural beliefs and practices.

parents’ needs.

Total sleep time declines from 18 to 13 hours a day by age 2.

Night wakings often increase at 6 months and again between

and 2 years, and then decline.

Cultural Variation in Infant Sleeping Arrangements

Parent–infant cosleeping is the norm for 90% of the world’s population.

Cultural emphasis on independent vs. interdependent self strongly influences infant sleeping arrangements.

Cosleeping is increasing in Western nations, perhaps because of a rise in breastfeeding.

Influences on Early Physical Growth

Heredity

Nutrition

Breastfeeding versus. bottle-feeding

Risk of overweight/obesity for chubby babies

Malnutrition: marasmus and kwashiorkor

Emotional well-being

Reasons to Breastfeed

Provides correct fat–protein balance.

Ensures nutritional completeness.

Promotes healthy physical growth.

Protects against many diseases.

Protects against faulty jaw development and tooth decay.

Ensures digestibility.

Smooths transition to solid food.

Are Chubby Babies at Risk for Later Obesity?

Recent evidence shows a relationship between rapid weight gain in infancy and later obesity.

Recommendations for parents:

Breastfeed for the first six months.

Avoid giving babies foods loaded with sugar, salt, and saturated fats.

Provide opportunities for energetic play.

Limit T V viewing time.

U.S. Public Policies and Infant Feeding Practices

2009 W I C policy changes:

Stronger breastfeeding counseling and educational materials

Food package enhancements that promote breastfeeding

Changes have led to increased rates of breastfeeding, and longer breastfeeding, among low-income mothers.

U.S. Public Policy Changes and Infant Feeding Practices

Figure 5.8

(Based on Whaley et al., 2012.)

Figure 5.8: Rates of breastfeeding by new mothers at WIC enrollment, as indicated by food package choice, before and after WIC policy changes

Malnutrition

Types	• Marasmus • Kwashiorkor • Iron-deficiency anemia • Food insecurity
Consequences	• Growth and weight problems • Poor fine-motor coordination • Learning and attention problems • More intense stress response • Passivity and irritability

Emotional Well-Being

Affection is as vital as food for healthy physical growth.

Growth faltering:

Weight, height, and head circumference are substantially below age-related growth norms.

Infants are withdrawn and apathetic.

A disturbed parent–child relationship often contributes.

Unhappy marriage and parental psychological disturbance are often involved.

Lasting cognitive and emotional difficulties may result.

The Steps of Classical Conditioning

Figure 5.9

Figure 5.9: The steps of classical conditioning

Operant Conditioning Terms

Reinforcer increases occurrence of a response.

Presenting desirable stimulus

Removing unpleasant stimulus

Punishment decreases occurrence of a response.

Presenting unpleasant stimulus

Removing desirable stimulus

Using Habituation to Study Infant Perception and Cognition

Figure 5.10

(Photo © Prashant Zi/Fotolia)

Figure 5.10: Using habituation to study infant perception and cognition

Imitation

Newborns have primitive ability to learn by copying another person’s behavior.

Neural mirroring systems may underlie early imitative capacities.

View of newborn imitation as a flexible, voluntary capacity remains controversial.

Capacity to imitate expands greatly over first two years.

The Sequence of Motor Development

Gross-motor development:

Crawling

Standing

Walking

Fine-motor development:

Reaching

Grasping

Table 5.2 Gross- and Fine-Motor Development in the First Two Years

Motor Skill	Average Age Achieved
Holds head erect, steady	6 weeks
Lifts self by arms Rolls from side to back	2 months
Grasps cube	3–4 months
Sits alone Crawls	7 months
Pulls to stand	8 months
Stands alone	11 months
Walks alone Builds two-cube tower	11–12 months
Scribbles vigorously	14 months
Jumps in place	23–24 months
Walks on tiptoe	25 months

Motor Skills as Dynamic Systems

Acquisition of increasingly complex systems of action

Each new skill is a joint product of four factors:

Central nervous system development

The body’s movement capacities

The child’s goals

Environmental supports for the skill

Cultural Variations in Motor Development

Home environment and infant rearing practices affect motor development.

Some cultures discourage rapid motor progress; others actively encourage it.

Western practice of having babies sleep on their backs to protect them from S I D S delays motor milestones.

Some Milestones of Reaching and Grasping

Figure 5.14

(Ages from Bayley, 1969; Rochat, 1989.)

Figure 5.14: Some milestones of reaching and grasping

Developments in Hearing

4–7 months	Sense of musical phrasing
6–8 months	“Screen out” sounds from nonnative languages
7–9 months	Divide the speech stream into wordlike units
10 months	Detect words that start with weak syllables

A Sensitive Period for Culture-Specific Learning

Perceptual sensitivity becomes attuned to information most often encountered:

Faces

Musical rhythms

Language

Babies are biologically prepared to “zero in” on socially meaningful perceptual distinctions.

Improvements in Vision

Visual Ability	Age of Maturation to Adultlike Levels
Focus	2 months
Color vision	4 months
Visual acuity	4 years
Scanning Tracking objects	Improves over first 6 months, as other abilities improve

Emergence of Depth Perception

Birth–1 month	Sensitivity to motion
2–3 months	Sensitivity to binocular depth cues
3–7 months	Sensitivity to pictorial depth cues

Development of Pattern Perception

3 weeks	• Poor contrast sensitivity • Prefers large, simple patterns
2 months	• Detects fine-grained detail • Prefers complex patterns
4 months	• Detects subjective boundaries that are not really present
12 months	• Detects familiar objects when two-thirds of drawing is missing

Appearance of Checkerboards to Very Young Infants

Figure 5.18

(Adapted from M. S. Banks & P. Salapatek, 1983, “Infant Visual Perception,” in M. M. Haith & J. J. Campos (Eds.), Handbook of Child Psychology: Vol. 2. Infancy and Developmental Psychobiology [4th ed.], New York: John Wiley & Sons, p. 504. Copyright © 1983 by John Wiley & Sons, Inc. Reproduced with permission of John Wiley & Sons, Inc.)

Figure 5.18: The way two checkerboards differing in complexity look to infants in the first few weeks of life

Subjective Boundaries in Visual Patterns

Figure 5.19

(Adapted from Ghim, 1990; Rose, Jankowski, & Senior, 1997.)

Figure 5.19: Subjective boundaries in visual patterns

Early Face Perception

Newborns respond to facelike structures but cannot discriminate a complex facial pattern from other complex patterns.

Around 3 months, infants make fine distinctions among features of different faces.

At 5 months, infants perceive emotional expressions as meaningful wholes, a capacity that expands by 7 months.

Early experience promotes perceptual narrowing with respect to gender and racial information.

Testing Infants’ Ability to Perceive Object Identity

Size and shape constancy are present in the first week of life.

Perception of object unity develops around 2 months.

At 5 months, infants can track objects traveling on a curvilinear course at varying speeds.

Experience enhances infants’ predictive eye tracking.

Testing Infants’ Ability to Perceive Object Unity

Figure 5.21

(Based on Johnson, 1997.)

Figure 5.21: Testing infants’ ability to perceive object unity

Intermodal Perception

Intermodal stimulation: simultaneous input from more than one modality or sensory system

Intermodal perception: capacity to perceive streams of multisensory input as integrated wholes

Newborns can detect amodal sensory properties.

Intermodal perception

develops rapidly in first year.

facilitates processing of both physical and social world.

Differentiation Theory of Infant Perception

Infants actively search for invariant features of the environment—those that remain stable.

As a result, babies detect patterns such as complex designs, individual faces.

Over time, baby differentiates among increasingly fine invariant features.

Perception is guided by discovery of affordances: the action possibilities offered by a situation.

Acting on the Environment Plays a Major Role in Perceptual Differentiation

Figure 5.22

Figure 5.22: Acting on the environment plays a major role in perceptual development

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