Human Development

Physical Development and Biological Aging

Physical Growth: Height and Weight Infants double their weight by four

months and triple it by their first birthday

Early childhood: girls are slightly smaller/lighter than boys

Middle/late childhood: children grow 2-3 inches per year and double their strength capacities

The Role of the Environment

Urban, middle SES first born children were taller than rural, low SES, later born children

Nutrition influences height and weight differences

Unusually Short Children

• Congenital factors

• Growth hormone deficiency

• Physical problems developed in

childhood

• Maternal smoking during pregnancy

• Emotional difficulty

Puberty

Rapid physical maturation Hormonal/bodily changes

Role of genes and environments

Pubertal Growth Spurt

Fig. 3.3

Changing Trends in Puberty

Onset of puberty beginning earlier

United States: menarche at 15 in 1840s, now

12½

Caucasian girls at average age of 10

African American girls at average age 8 to 9

**How does this impact development?

Body Image in Puberty

Throughout puberty…

Girls’ dissatisfaction increases — body fat increases

Boys’ satisfaction increases — muscle mass increases

What factors influence body image?

Early vs. Late Maturing Boys

Early maturing boys perceive themselves more positively and have more successful peer relationships than late maturing boys

Early Maturing Girls

Early maturing girls: At risk for smoking, drinking,

depression, eating disorders Tend to have older friends Earlier dating/sex Lower educational/occupational

attainment Higher incidence of mental disorders

Early Adulthood

Subtle physical changes Many reach peak of muscle tone

and strength in late teens and

twenties

Peak in joint functions in twenties

Decline in the thirties

Middle Adulthood

Lose height, gain weight Blood pressure/cholesterol increases Fertility declines:

Women: menopause Men: reduced sperm count (fertility is not

lost)

Late Adulthood

Increased risk for physical problems

Weight tends to drop after age 60

The Brain

Recent research:

Both heredity and environment shape the brain

The role of experience and brain plasticity

The Brain’s Four Lobes

Fig. 3.7

Functions of Lobes of the Cortex

Frontal lobes

Occipital lobes

Temporal lobes

Involved in voluntary movement, thinking, personality, and intentionality or purpose

Function in vision

Active role in hearing, language processing, and memory

Parietal lobesRoles in registering spatial location, attention, and motor control

The Neuron

Fig. 3.8

Experience and the Brain Mice in deprived vs. enriched

environments: differences in brain weight, neural connections and activity

Children reared in deprived environments have depressed brain activity (i.e. Romanian orphans) Can be reversed; brain plasticity/resilience

Experience and the Brain Exposure to trauma:

PTSD: reduced size of the hippocampus

Depression: Parts of the brain atrophy over time

Addiction: Changes in neurotransmitters

Pruning

Changes to the dendrites and synapses Connections are formed and

terminated

Dendritic Spreading

Fig. 3.11

The Brain in Adolescence

The adolescent brain is still growing

Emotional processing differences between adolescents (10-18 years) and adults (20-40 years)

Adolescents: Gut responses Adults: rational, reasoned responses

Differences in the parts of the brain used to process emotional information

The Brain in Adolescence

Adolescent emotions — Areas of the brain involved in emotional

regulation are still growing/changing

Poor self-control; seek rewards and pleasure

Seek novelty; increased risk-taking

Lack of practical experiences; immature

judgment **importance of parental involvement/limit setting

Preventing Brain Diseases

Positive emotions linked to longevity

Intellectual stimulation

Folic acid reduces risks and damage

Life Expectancy

Life expectancy — number of years that an average person born in a particular year will probably live

Impacted by heredity and environment

Life Expectancy

Females average 80 years, 74 years for males

Men are more likely to die from leading causes of death (respiratory diseases, accidents, suicide, cirrhosis of the liver, heart disease)

Role of lifestyle, workplace stress, heath habits

Centenarians

Individuals who live to 100: Women who have never married Ability to cope successfully with

stress Education, health, and lifestyle Individual personality traits

**Highest ratio in Okinawa: why?

Fig. 3.20

Risks of Dying from Cancer in Okinawa, Japan, and the United States