Week 2: Human Development Notes
Week 2: Human Development Notes
Core framing: nature vs. nurture
Nature: genetic factors influencing development.
Nurture: environmental factors influencing development.
Begin with prenatal influences before birth, then continue through lifespan.
Prenatal Development
Conception and early development
Conception occurs when a mature egg is released by the ovary and is fertilized by a sperm.
A fertilized egg is a zygote.
About days after conception, the zygote attaches to the uterine wall.
Beginning of the prenatal period corresponding to the start of the mother–fetus relationship: gestation is typically around .
Inner cells of the zygote form the embryo.
By approximately 40 days, the spine is visible and limbs begin to form.
By after conception, the embryo looks unmistakably human and is then termed a fetus.
In the fetal period, facial features, hands, and feet are formed; around the fourth month, the fetus weighs about and could fit in the palm of a hand.
Prenatal stages (Figure reference)
Zygote: Conception to
Embryo: through
Fetus: to birth
Placenta: formed by outer zygote cells attaching to the uterine wall; transfers nutrients and oxygen from mother to fetus; screens out many harmful substances.
Teratogens and prenatal risk
Teratogens are chemicals or agents that can cause harm during prenatal development.
Alcohol is a common teratogen; even light drinking can affect fetal brain development; heavy drinking increases risk for birth defects and mental retardation.
Fetal Alcohol Syndrome (FAS): incidence ≈ infants; characterized by a small, disproportioned head and lifelong brain abnormalities, leading to potential learning disabilities or behavioral problems later.
Environment and genetics
At each prenatal stage, both genetic and environmental factors influence development.
The placenta mediates nutrient/oxygen transfer and protection but cannot prevent all teratogenic effects.
Reflexes at birth (relating to early development and Locke’s tabula rasa concept)
Newborn reflexes are inborn, automatic responses to stimuli.
Key reflexes: rooting, sucking, grasping, Moro, Babinski.
Reflexes: Examples and Descriptions (from Figure 02)
Rooting reflex: When touched on the cheek, infant turns head toward touch and seeks to put the object in the mouth.
Sucking reflex: When an object is placed in the mouth, infant sucks on it.
Grasping reflex: If an object is placed in the palm or foot pad, infant grasps it.
Moro reflex: When startled, infant flings limbs out and rapidly retracts them to appear small.
Babinski reflex: When the sole of the foot is stroked, infant toes fan upward and out.
Cognitive Development: Piaget
Core idea
Children are active thinkers striving to construct more advanced understandings of the world.
Cognition develops through schemas and cognitive rules used to interpret experience.
Two key processes:
Assimilation: interpreting new experiences in terms of existing schemas.
Accommodation: adjusting schemas to incorporate new information.
Piaget’s stages of cognitive development
Sensorimotor Stage (birth to nearly 2 years)
Experiencing the world through senses and actions (looking, hearing, touching, mouthing, grasping).
Key developments: object permanence; stranger anxiety.
Typical Age Range:
Preoperational Stage (2 to about 6 or 7 years)
Representing things with words and images; intuitive rather than logical reasoning.
Key phenomena: egocentrism; lack of conservation; pretend play.
Concrete Operational Stage (about 6 or 7 to 11 years)
Thinking logically about concrete events; grasping concrete analogies; performing arithmetical operations.
Key feats: conservation; mathematical transformations.
Formal Operational Stage (about 12 through adulthood)
Abstract reasoning; capable of hypothetical propositions and deducing consequences; systematic reasoning.
Summary table highlights (typical age ranges + developmental phenomena)
Sensorimotor: Birth–; Object permanence; Stranger anxiety.
Preoperational: ; Egocentrism; Pretend play.
Concrete Operational: ; Conservation; Logical thinking with concrete objects.
Formal Operational: ; Abstract reasoning; Hypothetical-deductive reasoning.
Social Development: Erik Erikson’s Psychosocial Theory
Core idea
Each life stage presents a psychosocial task/crisis; successful resolution yields a virtue that contributes to healthy personality.
Failure to resolve a stage may hinder later stages, but crises can be resolved later in life.
Erikson’s stages (approximate age, task, and description)
Infancy: Trust vs. Mistrust (to 1 year)
If needs are met consistently, child develops basic trust.
Toddlerhood: Autonomy vs. Shame and Doubt (1–3 years)
Children learn to exercise will and do things for themselves or doubt abilities.
Preschool: Initiative vs. Guilt (3–6 years)
Initiate tasks and carry out plans; otherwise feel guilty about independence.
Elementary School: Industry vs. Inferiority (6 years to puberty)
Enjoy applying oneself to tasks; may feel inferior otherwise.
Adolescence: Identity vs. Role Confusion (teen years into 20s)
Refine sense of self by testing roles; integration into a single identity; otherwise confusion.
Young Adulthood: Intimacy vs. Isolation (20s to early 40s)
Form close relationships and gain capacity for intimate love; otherwise social isolation.
Middle Adulthood: Generativity vs. Stagnation (40s to 60s)
Contribute to world through family/work; otherwise a sense of lack of purpose.
Late Adulthood: Integrity vs. Despair (late 60s and up)
Reflect on life; sense of satisfaction or failure.
Moral Development: Kohlberg’s Theory
Focus: development of moral reasoning, not behavior per se.
Heinz dilemma as a representative scenario:
A husband (Heinz) steals a drug to save his dying wife when he cannot afford it.
Questions explored: Should Heinz have stolen? Would it differ if the person dying were a stranger? What if police arrest the chemist for murder?
Kohlberg’s levels and stages (with brief descriptions)
Pre-conventional (morality external to self):
Stage 1: Obedience and Punishment Orientation
Moral reasoning to avoid punishment; self-centered.
Stage 2: Instrumental Relativist Orientation
Morality tied to reward; interests of others considered for personal gain.
Conventional (internalized by social expectations):
Stage 3: Good Boy-Nice Girl Orientation
Seek approval from others; care, loyalty, trust valued; avoid disapproval.
Stage 4: Law and Order Orientation
Follow rules because rules exist; duty/justice; maintain social order.
Post-conventional (internal, self-defined principles):
Stage 5: Social Contract Orientation
Laws are important but can be changed if they violate liberty or rights of individuals.
Stage 6: Universal Ethical Principle Orientation
Follow conscience and universal ethical principles even if they conflict with laws.
Individual may weigh altruism and the good of the group against strict rights of others.
Attachment Theory
Foundational thinkers and experiments
Konrad Lorenz: imprinting; some infant animals form attachments to objects or individuals during a critical period after birth.
John Bowlby (1958): attachment theory linking early infant separations from the mother to later social, emotional, and cognitive development; stress of separation may lead to maladjustment.
Harry Harlow (1950s): rhesus monkeys; tested whether nourishment or contact comfort drives attachment.
Method: 8 infant monkeys separated at birth; two surrogate mothers: wire with bottle (feeding) and cloth (comfort).
Findings: Monkeys spent more time with cloth surrogate, even when wire surrogate fed; in stressful situations, sought comfort from cloth surrogate.
Conclusion: Contact comfort is crucial for attachment beyond feeding.
Mary Ainsworth: Strange Situation experiment with human infants
Observed reactions when parents left and returned in novel environments.
Attachment categories:
Secure attachment: ≈ ; explores while parent present, distressed when separated, seeks parent upon return.
Avoidant attachment: ≈ ; resists being held, explores environment, does not seek comfort on return.
Anxious/Ambivalent (Resistant) attachment: ≈ ; highly distressed by separation, resists comfort on return.
Parenting Styles (Baumrind)
Three primary styles described, with outcomes for children
Permissive
Description: Few clear guidelines; rules are inconsistent; unpredictable responses.
Child qualities: poor emotion regulation (under-regulated); rebellious; low persistence; antisocial behaviors.
Authoritarian
Description: Strict standards; punishment more common than reinforcement; obedience valued over discussion.
Child qualities: anxious, withdrawn, unhappy; poorer frustration tolerance; good in school in some cases; less likely to engage in antisocial activity.
Authoritative
Description: Set, consistent standards that are reasonable and explained; encourage independence within rules; balanced praise and punishment; explanations encouraged.
Child qualities: lively, self-confident, well-developed emotion regulation, social skills; less rigid on gender traits; generally well-adjusted.
Infancy: Motor & Sensory Development
Distinguish sensation vs perception
Sensation: interaction with sensory receptors.
Perception: interpretation of sensed information.
Sensory development in infancy
Sight: least developed at birth; newborns see approximately and prefer faces or highly interesting images.
Hearing: most developed at birth; prenatal exposure to mother’s voice.
Touch/pain: physiological indicators show pain; touch is necessary and comforting.
Taste/smell: distinguish flavors; prefer sweet tastes; easily identify mother’s smell.
Early Childhood: Play, Parenting, and Development of Learning/Intelligence
Role of play and healthy parenting for development.
Language and cognitive growth supported by play, exploration, and caregiver interaction.
Developmental disorders to be aware of:
Autism Spectrum Disorder (ASD): difficulties in communication and social cues; language development differences.
Dyslexia: neurobiological origin; difficulties in word recognition and decoding; spelling challenges.
Attention Deficit Hyperactivity Disorder (ADHD): neurological/behavioral; challenges with attention, impulse control, and task persistence.
Social and cognitive labeling effects (self-fulfilling prophecy) when labeling children can influence outcomes.
Adolescence: Brain and Sexual Development
Brain development during adolescence
Prefrontal cortex: involved in decision-making and higher-order cognition; continues developing into young adulthood.
Myelination: improves processing speed.
Synaptic pruning: strengthens efficient neural connections.
Limbic system develops earlier, influencing emotion processing, rewards, and risk assessment.
Pubertal hormones affect amygdala and associated emotional responses.
Dopamine: “feel good” chemical; high production linked to reward-seeking and risk-taking.
Serotonin: calming chemical; balances dopamine; extreme behaviors may arise when imbalanced.
Sleep patterns
Melatonin shifts lead to later sleep; teens typically need of sleep; sleep deprivation increases impulsivity and negative emotions.
Body image and health risks
Negative body image and body dissatisfaction common; linked to poor nutrition and atypical eating patterns.
Eating disorders: four examples discussed:
Muscle dysmorphia
Bulimia nervosa (binge/purge cycles; often normal weight)
Anorexia nervosa (distorted body image; underweight)
Binge-eating disorder (overeating; often with anxiety/depression/obesity)
Health consequences: anorexia is the most fatal mental disorder; suicide risk higher among some cases; metabolic and cardiovascular risks with other disorders.
Sexual development and education
Sexual interactions influenced by body image and media portrayals; STI risk for sexually active teens; sex education is multifaceted (not only pregnancy prevention).
Freud and adolescent sexuality (brief reference)
Genital stage of psychosexual development; ego and superego maturation; secondary-process thinking and desires.
Social and relational development in adolescence and beyond (brief overview)
Friendships, intimate relationships, and responsibilities to family and future adult roles.
Developmental Tasks in Early and Middle Adulthood
Early adulthood (Havighurst): developmental tasks include
Achieving autonomy, establishing identity, emotional stability
Developing a career, finding intimacy, joining a community/group
Establishing a residence and managing a household
Becoming a parent and rearing children
Making marital or relationship adjustments and learning to parent
Middle adulthood (Lachman): common challenges
Losing parents and experiencing grief
Launching children into independent lives; adjusting to a home without children
Dealing with adult children who return home
Becoming grandparents; preparing for late adulthood
Acting as caregivers for aging parents or spouses
These transitions reflect potential reorientation in outlook, investment, attitudes, and relationships, influenced by circumstances beyond control.
The Most Common Causes of Death and Death Processes
Historical vs present patterns
In 1900, infectious diseases were the most common causes of death.
By , chronic diseases are more prevalent as leading causes.
Top 10 deadliest diseases worldwide (2015): heart disease, stroke, lower respiratory infections, COPD, trachea/bronchus/lung cancers, diabetes, Alzheimer’s/dementia, dehydration, tuberculosis, cirrhosis.
Variability by age group: top causes differ across ages; unintentional injuries are a leading cause across a broad range of ages.
Definitions of death in this context:
Physiological death: vital organs cease to function; may occur within or less; includes:
Digestive and respiratory system shutdown
Circulation slows, mottling may occur
Agonal breathing: gasping, labored breaths due to brainstem reflexes
Brain death: no brain activity; clinically dead
Vegetative state: cerebral cortex no longer registers electrical activity; brainstem may still be active
Social death: others withdraw socially; terminal illness outcomes lead to reduced interaction even before physical death
Psychological death: dying person may withdraw from life and accept death; can precede physiological death; interventions aimed at empowerment can improve mental health and perceived control
Note: Many age ranges, percentages, and numeric examples are drawn directly from the transcript. Where applicable, numerical concepts are presented in LaTeX format for study-ready notation, e.g., of sleep for adolescents, secure attachments, incidence of Fetal Alcohol Syndrome, and stage descriptors with their associated age spans accordingly.