Overview
This lecture introduces developmental psychology, focusing on biological development and how humans change physically from conception through adulthood and aging. It is the first in a three-part series, emphasizing the scientific study of human growth, change, and stability across the lifespan.
Domains of Human Development
- Developmental psychology examines how people change and grow from conception to death.
- Three main domains:
- Physical (biological) development: Growth and changes in the body, brain, senses, motor skills, and health.
- Cognitive development: Learning, attention, memory, language, thinking, reasoning, and creativity.
- Psychosocial development: Emotions, personality, and social relationships.
- Each domain interacts with the others, and development is seen as a lifelong process.
Theories and Patterns of Development
- Normative psychologists study large groups to determine average ages for developmental milestones (e.g., crawling, walking, speaking, puberty).
- Biological milestones (like puberty) are generally universal, while social milestones (like starting school) can vary by culture.
- There is debate over how development occurs:
- Continuous development: Children grow gradually, steadily adding new skills and knowledge over time.
- Discontinuous (stage) development: Children develop in distinct stages, with rapid changes at certain points followed by periods of slower growth.
- Theories also consider whether development is universal (the same for everyone) or varies based on genetics and environment.
- Stage theories suggest a universal sequence, but research shows that culture and environment can influence the timing and course of development.
Biological/Physical Development: Stages and Milestones
- Prenatal development is divided into three stages:
- Germinal stage (first 1–2 weeks): Begins at conception when a sperm fertilizes an egg, forming a zygote. The zygote divides and differentiates, eventually implanting in the uterus.
- Embryonic stage: The zygote becomes an embryo. Organs begin to form, the heart starts beating, and the placenta develops to provide nutrients and remove waste.
- Fetal stage: Major growth and maturation of organs, brain, and senses. Key milestones include the development of facial expressions, thumb-sucking, gender detection, and regular sleep-wake cycles.
- Prenatal milestones:
- Heartbeat detectable in the first trimester.
- Facial expressions and thumb-sucking by 14–16 weeks.
- Gender may be detected at 16 weeks.
- Lungs and senses develop rapidly in the third trimester.
- By 37 weeks, the baby is considered early term; full term is 39 weeks.
- Babies born before 27 weeks have low survival rates; those born after 30 weeks usually survive.
- Teratogens (e.g., tobacco, alcohol, drugs) can cross the placenta and cause serious health problems, such as fetal alcohol syndrome (FAS), which leads to physical and cognitive abnormalities.
- FAS symptoms include abnormal facial features, smaller head size, learning issues, poor impulse control, and lower IQ.
Infancy and Childhood Development
- Newborn reflexes help infants survive:
- Rooting (turning toward touch on cheek)
- Sucking (on objects near the mouth)
- Grasping (holding objects placed in the hand)
- Moro (startle response)
- Sensory abilities:
- Vision is least developed at birth.
- Babies can hear and prefer their mother's voice; they can also distinguish their mother's smell.
- Motor development:
- Gross motor skills: Progress from kicking, rolling, and crawling to standing, walking, running, skipping, and jumping.
- Fine motor skills: Develop from reflexive grasping to voluntary grasp, picking up objects, scribbling, cutting, writing, and tying shoes.
- Brain development:
- Rapid neural growth (blooming) in infancy and toddlerhood, forming many new connections.
- Pruning occurs in childhood and adolescence, reducing unused neural pathways for greater efficiency.
- By age 2, the brain is about 55% of adult size; by age 6, about 90%.
Adolescence and Puberty
- Puberty is marked by dramatic hormonal and physical changes:
- Adrenarchy: Activation of adrenal glands, leading to increased adrenal androgens (weak testosterone), which contribute to secondary sexual characteristics (e.g., body hair, sweat glands).
- Begins around ages 6–9 in girls, a year later in boys.
- Gonadarche: Activation of the hypothalamus and pituitary gland, leading to reproductive maturity.
- Begins around ages 8–14 in girls (average 11), 9–15 in boys (average 12).
- Hormones like estrogen and testosterone influence physical appearance, brain, and behavior.
- Growth axis activation: Triggers a growth spurt (around age 12 in girls, 14 in boys).
- Key puberty milestones:
- Girls: Breast and hip development, menarche (first menstruation, usually ages 13–16), signaling fertility.
- Boys: Facial hair, voice deepening, spermarche (first sperm production, ages 12–16).
- Environmental factors, such as family stress or conflict, can influence the timing of puberty.
Adulthood and Aging
- Adulthood is divided into early, middle, and late stages:
- Early adulthood: Physical maturation is complete by around age 20. Physical abilities (muscle strength, reaction time, sensory abilities) peak. The brain continues to mature, especially the prefrontal cortex, which handles planning, problem-solving, and impulse control.
- Middle adulthood: Fertility peaks in the 20s and 30s, declines after age 35. Women experience perimenopause (declining fertility) and menopause (end of fertility, usually around age 50), marked by symptoms like hot flashes and mood swings. Some men experience andropause (testosterone decline), but it is not universal.
- Late adulthood: Aging leads to declines in brain mass and synaptic connections, especially after age 60. The frontal lobe and hippocampus shrink, affecting memory and higher cognitive functions. Myelin deteriorates, and neurons retract dendrites.
- The process of aging is complex and individualized, influenced by both biological and environmental factors.
Key Terms & Definitions
- Normative milestones: Average ages for major developmental events (e.g., walking, puberty).
- Teratogens: Substances that can harm prenatal development (e.g., alcohol, drugs).
- Blooming: Rapid formation of neural connections in infancy and toddlerhood.
- Pruning: Reduction of unused neural pathways to improve brain efficiency.
- Adrenarchy: Hormonal changes before puberty, involving adrenal glands.
- Gonadarche: Onset of reproductive maturity, involving the hypothalamus and pituitary gland.
- Menarche: First menstrual period in females, marking fertility.
- Spermarche: Beginning of sperm production in males.
- Menopause: End of menstrual cycles and fertility in women.
- Andropause: Age-related decline in testosterone in some men.
Action Items / Next Steps
- Reflect: How are you the same and how are you different now compared to when you were 15 years old?
- Prepare for the next lecture, which will focus on cognitive development.