1. PHYSICAL DEVELOPMENT: THE BRAIN, BODY, MOTOR SKILLS, AND SEXUAL DEVELOPMENT

2. AN OVERVIEW OF MATURATION AND DEVELOPMENT
Changes in Height and Weight
Rapid increase in height and weight over first two years
Growth is more gradual during middle childhood
Puberty (early adolescence) there is another rapid growth spurt

3. Figure 5.1 Gain in height per year by males and females from birth through adolescence. At age 10 ½ , girls begin their growth spurt. Boys follow some 2 ½ years later and grow faster than girls once their growth begins. Based on a figure in Archives of the Diseases in Childhood, 41, by J. M. Tanner, R. H. Whitehouse, and A. Takaishi, 1966, pp

4. AN OVERVIEW OF MATURATION AND DEVELOPMENT
Changes in Body Proportions
Cephalocaudal – head downward growth
At birth, head and legs each represent 25% of body length
At adulthood, head is 12%, legs 50%
Proximodistal – center outward growth
Internal organs followed by limbs
Trend reverses in puberty – hands and feet followed by limbs, then trunk

5. Figure 5.2 Proportions of the human body from the fetal period through adulthood. The head represents 50 percent of body length at 2 months after conception but only 12 to 13 percent of adult stature. In contrast, the legs constitute about 12 to 13 percent of the total length of a 2-month-old fetus, but 50% of the height of a 25-year-old adult.

6. AN OVERVIEW OF MATURATION AND DEVELOPMENT
Skeletal Development
Bones lengthen, thicken, and harden with age completing most growth by 18
Skull has fontanelles (soft spots for childbirth), and sutures (seams) for expansion for brain growth
Ankles, feet, wrists, hands develop more bones

7. Figure 5.3 X-rays showing the amount of skeletal development seen in (A) the hand of an average male infant at 12 months or an average female infant at 10 months and (B) the hand of an average 13-year-old male or an average 10½-year-old female.

8. AN OVERVIEW OF MATURATION AND DEVELOPMENT
Muscular Development
Born with all muscle fibers
Increase in density and size, particularly during growth spurt of adolescence
Variations in Physical Development
Structures develop at different rates
Individuals develop at different rates
Cultural variations also exist

9. Figure 5. 4 Growth curves for different body systems
Figure 5.4 Growth curves for different body systems. Each curve plots the size of a group of organs or body parts as a percentage of their size at age 20 (which is the 100 percent level on the vertical scale). The “general” curve describes changes in the body’s size as well as the growth of respiratory and digestive organs and musculature. The brain and head grow more rapidly than the body in general, and the reproductive organs are the slowest to reach adult size. (The lymph nodes and other parts of the lymphatic system, which function as part of the immune system, also grow rapidly and actually exceed adult size during late childhood and adolescence.) From Growth at Adolescence, 2nd ed., by J. M. Tanner, Oxford, England: Blackwell. Copyright © 1962 by Blackwell Scientific Publications, Inc. Reprinted by permission of Blackwell Science, Ltd.

10. Figure 5.5 There are large individual variations in the timing of the adolescent growth spurt, as we see in comparing the stature of these boys of the same age.

11. DEVELOPMENT OF THE BRAIN
Brain Growth Spurt: Last three prenatal months and first two years of life
Neural Development and Plasticity
Neurons – basic unit of brain/nervous system; most present at birth
Form synapses (connective spaces) with other neurons
Glia – nourish neurons and encase them in myelin; form throughout life

12. DEVELOPMENT OF THE BRAIN
Neural Development: Cell Differentiation and Synaptogenesis
Neurons can serve any neural function
Synaptogenesis – formation of synapses
More formed than needed
Roughly half die; some stand in reserve – injury or new skills
Plasticity – cells are responsive to experience (allows change in brain)

13. DEVELOPMENT OF THE BRAIN
Neural Plasticity: The Role of Experience
Reisen – dark reared chimp study
Beyond seven months, atrophy of retina and optic nerve was irreversible
Increased head circumference in children from high SES homes

14. DEVELOPMENT OF THE BRAIN
Brain Differentiation and Growth
At birth, brain associated with biological functioning is most developed
Cerebrum and cerebral cortex (higher brain centers)
Primary motor areas; primary sensory areas mature first

15. DEVELOPMENT OF THE BRAIN
Myelinization
At birth – pathways between sense organs and brain are myelinated
Pathways between muscles and brain are next
Reticular formation and frontal cortex
Needed for long term concentration
Not fully myelinated at puberty
Enhances efficiency between emotive and regulatory areas of the brain

16. DEVELOPMENT OF THE BRAIN
Cerebral Lateralization
Cerebrum consists of two hemispheres connected by the corpus callosum
Each covered by a cerebral cortex
Left – right side of body; speech, hearing, verbal memory, decision making, positive emotions
Right – left side of body; visual-spatial information, music, touch, negative emotions
Lateralization increases with age

17. Figure 5.6 Lateral view of the left cerebral cortex and some of the functions that it controls. Although the cerebellum and spinal cord are not part of the cerebral cortex, they serve important functions of their own.

18. Sequence of motor skills is the same for all infants
MOTOR DEVELOPMENT
Sequence of motor skills is the same for all infants
Large individual variation of ability to perform motor skills within children
Rate of motor development not strongly related to future development outcomes

19. Table 5.1 Age Norms (in Months) for Important Motor Developments (Based on European American, Latino, and African American Children in the United States). Sources: Bayley, 1993; Frankenberg and Dodds, 1967.

20. Basic Trends in Locomotor Development
Cephalocaudal – head-downward
Exception is coordination of hip movement before shoulder movement
Due to structure of joints
Proximodistal – center-outward

21. The Maturational Viewpoint
MOTOR DEVELOPMENT
The Maturational Viewpoint
Motor development is a genetically programmed sequence of events
The Experiential/Practice Hypothesis
Maturation and practice are important
Dynamical Systems Theory
New skills are constructed as infants actively reorganize existing capabilities
Desire is to achieve a goal

22. Fine Motor Development
Development of Voluntary Reaching
Prereaching is replaced by voluntary reaching (3 months of age)
Development of Manipulatory Skills
Claw-like ulnar grasp is replaced by the pincer grasp (near end of first year)

23. Psychological Implications of Early Motor Development
Motor skills allow for fun social interaction
Provide evidence of normal development
Fosters perceptual, cognitive, and social development
Optic flow, distance, spatial memory

24. Beyond Infancy: Motor Development in Childhood and Adolescence
Each year, skills improve
Large muscles, eye-hand coordination
Genders equal in physical ability until puberty
Males continue to improve
Females level off or decline
Biology – less muscle mass
Gender-role socialization: fewer athletic activities

25. RESEARCH: SPORTS PARTICIPATION AND SELF-ESTEEM AMONG ADOLESCENT FEMALES
Earlier participation in sports associated with higher self-worth in college
Participation associated with increased physical competencies
Development of more favorable body image
Acquisition of desirable masculine traits
Assertiveness
All correlated with college self-esteem

26. PUBERTY: THE PHYSICAL TRANSITION FROM CHILD TO ADULT
The Adolescent Growth Spurt
Begins at about 10 ½ for females
Begins at about 13 for males
Increase in height and weight
Bodies and faces appear more adultlike
Puberty – point at which sexual maturity is reached

27. PUBERTY: THE PHYSICAL TRANSITION FROM CHILD TO ADULT
Sexual Maturation
Timed with growth spurt, predictable pattern
Girls
Onset of breast and pubic hair development
Widening of hips, enlarging of uterus, and vagina
Menarche (first menstruation)
Completion of breast growth

28. PUBERTY: THE PHYSICAL TRANSITION FROM CHILD TO ADULT
Sexual Maturation
Boys
Development of testes and scrotum
Emergence of pubic hair
Growth of penis, sperm production
Appearance of facial hair
Lowering of voice
Large individual differences in timing (both genders)

29. PUBERTY: THE PHYSICAL TRANSITION FROM CHILD TO ADULT
Secular Trends: Are We Maturing Earlier?
Reaching sexual maturity earlier in industrialized societies than in the past
Also growing taller and heavier
Due to
Improved nutrition
Improved health care

30. CAUSES AND CORRELATES OF PHYSICAL DEVELOPMENT
Biological Mechanisms
Effects of Individual Genotypes
Set limits for height and rate of maturation
Hormonal Influences: The Endocrinology of Growth
Pituitary gland releases growth hormone, stimulates production of estrogen, testosterone, and androgen

31. Figure 5.7 Hormonal influences on physical development.

32. CAUSES AND CORRELATES OF PHYSICAL DEVELOPMENT
Environmental Influences
Problems of Undernutrition
Catch-up growth if mild and short-term
Marasmus – not enough calories or protein; small, impaired social and intellectual development
Kwashiorkor – not enough protein; fluid collects in face, legs, and abdomen
Vitamin and mineral deficiencies
Zinc – very slow growth
Iron deficiency anemia – social and intellectual impacts

33. CAUSES AND CORRELATES OF PHYSICAL DEVELOPMENT
Environmental Influences
Problems of Overnutrition
Obesity – 20% above ideal weight
Illnesses
If adequately nourished, most do not affect growth long term

34. CAUSES AND CORRELATES OF PHYSICAL DEVELOPMENT
Environmental Influences
Emotional Stress and Lack of Affection
Nonorganic failure to thrive – before 18 months of age
Impatient, hostile caregivers cause infants to withdraw
Deprivation dwarfism – 2–15 years of age; lack of positive involvement with caregiver