Infants, Children, and Adolescents Eighth Edition Chapter 5 Physical Development in Infancy and Toddlerhood

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: Major milestones in brain development Figure 5.3 (Based on Thompson & Nelson, 2001.)

Major Measures of Brain Functioning Electroencephalogram (EEG) Event-related potentials (ERPs) Functional magnetic resonance imaging (fMRI) Positron emission tomography (PET) Near-infrared spectroscopy (NIRS)

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

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: Relationship of age at adoption to mental test scores at ages 6 and 11 among British and Romanian adoptees Figure 5.7 (Adapted from Beckett et al., 2006.)

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 1½ 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 vs. 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 TV viewing time.

U.S. Public Policies and Infant Feeding Practices 2009 WIC 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: Rates of breastfeeding by new mothers at WIC enrollment, as indicated by food package choice, before and after WIC policy changes Figure 5.8 (Based on Whaley et al., 2012.)

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: The steps of classical conditioning Figure 5.9

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: Using habituation to study infant perception and cognition Figure 5.10 (Photo © Prashant Zi/Fotolia)

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

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 SIDS delays motor milestones.

Some Milestones of Reaching and Grasping Figure 5.14: Some milestones of reaching and grasping Figure 5.14 (Ages from Bayley, 1969; Rochat, 1989.)

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

Subjective Boundaries in Visual Patterns Figure 5.19: Subjective boundaries in visual patterns Figure 5.19 (Adapted from Ghim, 1990; Rose, Jankowski, & Senior, 1997.)

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: Testing infants’ ability to perceive object unity Figure 5.21 (Based on Johnson, 1997.)

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

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