Development Across the Lifespan

Prenatal Development

Prenatal development proceeds through three stages. Germinal stage (conception to 2 weeks): the zygote undergoes rapid cell division and implants in the uterine wall. Embryonic stage (2-8 weeks): organogenesis occurs; all major organs and body systems form, making this the period of greatest vulnerability to teratogens -- environmental agents that cause birth defects (alcohol producing fetal alcohol syndrome, thalidomide causing limb deformities, rubella causing cardiac and sensory defects). Fetal stage (9 weeks to birth): growth and refinement of existing structures; the fetus becomes viable around 24 weeks. Newborns exhibit innate reflexes including rooting (turning toward cheek touch), sucking, Moro (startle), Babinski (toes fan upward when sole stroked), and grasping. These reflexes indicate neurological integrity and most disappear within the first year as cortical control develops.

Attachment Theory

Attachment is the enduring emotional bond between infant and caregiver that serves as a secure base for exploration. Bowlby proposed attachment is biologically programmed, evolving because it promotes survival. Ainsworth's Strange Situation procedure identified four attachment styles through systematic separations and reunions. Secure attachment (65%): infant uses caregiver as secure base, is distressed by separation, and is easily comforted upon reunion -- associated with responsive, sensitive caregiving. Insecure-avoidant (20%): infant appears indifferent to caregiver's departure and avoids contact upon reunion -- linked to rejecting or intrusive caregiving. Insecure-ambivalent/resistant (10-15%): infant is intensely distressed by separation, ambivalent upon reunion, simultaneously seeking and resisting contact -- associated with inconsistent caregiving. Disorganized/disoriented (5%): infant shows confused, contradictory behaviors such as freezing or approaching while looking away -- linked to abuse, neglect, or severely frightening parenting. Harlow's monkey experiments demonstrated that contact comfort, not just feeding, drives attachment: infant monkeys preferred the soft cloth surrogate without food over the wire surrogate that provided milk.

Piaget's Cognitive Development

Piaget's stage theory proposes four qualitatively distinct stages where children actively construct understanding through assimilation (fitting new information into existing schemas) and accommodation (modifying schemas to fit new information). Sensorimotor (0-2 years): learning through senses and motor actions; object permanence -- understanding objects exist when out of sight -- develops around 8-12 months, marked by the A-not-B error before mastery. Preoperational (2-7 years): symbolic thought emerges (pretend play, language) but children remain egocentric (difficulty taking others' perspectives, demonstrated by the three mountains task), show animism (attributing life to inanimate objects), and lack conservation -- understanding that quantity remains constant despite changes in appearance (liquid in different-shaped containers, number despite spreading). Concrete operational (7-11 years): logical reasoning about concrete objects develops; conservation, reversibility, classification, and seriation are mastered. Cannot reason abstractly. Formal operational (11+ years): abstract, hypothetical, and systematic reasoning emerges. Adolescents can perform hypothetico-deductive reasoning (the pendulum problem) and think about possibilities beyond present reality.

Erikson's Psychosocial Development

Erikson proposed eight psychosocial stages spanning the entire lifespan, each defined by a central conflict or crisis whose resolution shapes personality and social functioning. Trust versus mistrust (0-1 year): consistent, responsive caregiving builds trust that the world is safe and predictable. Autonomy versus shame and doubt (1-3 years): toddlers develop independence through self-care skills; overprotective or shaming parenting fosters doubt. Initiative versus guilt (3-6 years): children assert power and control through directing play and social interactions; over-criticism produces guilt. Industry versus inferiority (6-12 years): competence in academic and social tasks builds confidence; repeated failure or negative comparison yields inferiority. Identity versus role confusion (12-18 years): adolescents explore and commit to a coherent sense of self; failure to integrate roles produces confusion. Intimacy versus isolation (young adulthood): forming close, committed relationships. Generativity versus stagnation (middle adulthood): contributing to the next generation through parenting, mentoring, and productive work. Integrity versus despair (late adulthood): reflecting on life with a sense of fulfillment or regret. MCAT emphasis is on identity versus role confusion during adolescence and integrity versus despair in late adulthood.

Kohlberg's Moral Development

Kohlberg's stage theory of moral reasoning, presented via the Heinz dilemma, describes three levels each with two stages. Preconventional level: moral reasoning is self-centered. Stage 1 (punishment-obedience orientation): right is what avoids punishment. Stage 2 (instrumental-relativist orientation): right is what satisfies one's own needs -- you scratch my back, I'll scratch yours. Conventional level: moral reasoning is based on social relationships and norms. Stage 3 (good boy/nice girl orientation): right is what gains approval from others, maintaining interpersonal relationships. Stage 4 (law-and-order orientation): right is obeying laws and maintaining social order. Postconventional level: moral reasoning is based on abstract ethical principles. Stage 5 (social-contract orientation): laws are social contracts that should promote the greatest good; unjust laws can be changed. Stage 6 (universal ethical principle orientation): right is determined by self-chosen ethical principles of justice, equality, and human dignity, even when they conflict with laws. Critics (Gilligan) note Kohlberg studied only males and that care-based morality may represent a different, not lower, ethical framework.

Adolescence

Adolescence is the transition between childhood and adulthood marked by puberty, cognitive development, and identity formation. Puberty triggers primary sex characteristics (reproductive organs) and secondary sex characteristics (breast development, voice changes, body hair) driven by hormonal changes in the hypothalamic-pituitary-gonadal axis. Brain development features synaptic pruning (eliminating unused connections increasing efficiency) and frontal lobe myelination continuing into the early twenties, explaining heightened risk-taking and emotional reactivity relative to still-developing impulse control. Erikson's identity versus role confusion captures the central psychosocial task: adolescents explore and commit to an integrated sense of self. Marcia expanded this into four identity statuses based on exploration and commitment: identity achievement (explored and committed), moratorium (exploring without commitment), foreclosure (committed without exploration, adopting parents' values), and identity diffusion (neither exploring nor committed). Elkind described adolescent egocentrism including the imaginary audience (belief that everyone is watching and evaluating) and personal fable (belief that one's experiences are unique and that one is invulnerable).

Aging and Death

Late adulthood involves cognitive, social, and physical changes. Crystallized intelligence (accumulated knowledge and skills) remains stable or increases; fluid intelligence (novel problem-solving and processing speed) declines with age. Memory changes are selective: working memory and episodic memory decline, while semantic memory and procedural memory remain relatively intact. Socioemotional selectivity theory (Carstensen) proposes that as time horizons shrink, older adults prioritize emotionally meaningful relationships and goals over knowledge acquisition. Erikson's final stage, integrity versus despair, frames life review as the central task: those who find meaning and coherence achieve wisdom and acceptance; those who dwell on regrets face despair. Kubler-Ross described five stages of grief in terminal illness -- denial, anger, bargaining, depression, and acceptance -- though these stages are neither linear nor universal; individual grief trajectories vary widely. The dual-process model of grief alternates between loss-oriented coping (grieving the loss) and restoration-oriented coping (building a new life).

How it works

Developmental psychology on the MCAT requires recognizing which theory applies to a given scenario and distinguishing stage descriptions by age and defining features. For Piaget, match the cognitive limitation to the stage: no object permanence is sensorimotor, no conservation is preoperational, inability to think abstractly is concrete operational. For Erikson, identify the psychosocial conflict from the age and the described struggle -- a teenager questioning career and values is identity versus role confusion. For attachment, map behavioral patterns to Ainsworth's classification: indifferent infant is avoidant, ambivalent infant is resistant, confused infant is disorganized. For Kohlberg, decode the reasoning, not just the decision: avoiding punishment is Stage 1, conforming for approval is Stage 3, appealing to universal principles is Stage 6. Apply the bio-psycho-social model: development is shaped by biological maturation, cognitive growth, and social context interacting over time.

How it works

Developmental psychology on the MCAT requires recognizing which theory applies to a given scenario and distinguishing stage descriptions by age and defining features. For Piaget, match the cognitive limitation to the stage: no object permanence is sensorimotor, no conservation is preoperational, inability to think abstractly is concrete operational. For Erikson, identify the psychosocial conflict from the age and the described struggle -- a teenager questioning career and values is identity versus role confusion. For attachment, map behavioral patterns to Ainsworth's classification: indifferent infant is avoidant, ambivalent infant is resistant, confused infant is disorganized. For Kohlberg, decode the reasoning, not just the decision: avoiding punishment is Stage 1, conforming for approval is Stage 3, appealing to universal principles is Stage 6. Apply the bio-psycho-social model: development is shaped by biological maturation, cognitive growth, and social context interacting over time.

Comparisons

• Biology (Nervous system): Synaptic pruning during adolescence and delayed prefrontal myelination explain heightened risk-taking. The Moro, rooting, and Babinski reflexes indicate neurological integrity in newborns.
• Biology (Reproduction): Teratogen vulnerability maps to embryonic organogenesis. Fetal alcohol syndrome is the leading preventable cause of intellectual disability.
• Sociology: Vygotsky's sociocultural theory and Erikson's psychosocial stages emphasize that development is embedded in social context -- culture, family, and institutions shape the developmental path.
• Research Methods: Longitudinal designs follow the same individuals over time to track developmental change; cross-sectional designs compare different age groups at one time point. Each has distinct confounds (cohort effects versus attrition).

Common confusions

• "Conservation develops in the sensorimotor stage." Conservation -- understanding that quantity remains constant despite changes in appearance -- develops in the concrete operational stage (7-11 years). Preoperational children lack conservation.
• "Erikson's identity versus role confusion occurs in middle adulthood." Identity versus role confusion is the adolescent crisis (12-18 years). Middle adulthood is generativity versus stagnation.
• "Insecure-avoidant attachment is the same as disorganized attachment." Avoidant infants appear indifferent and avoid contact. Disorganized infants show contradictory, confused behaviors (freezing, approaching while looking away). They reflect different caregiving histories.
• "Kohlberg assessed moral behavior, not reasoning." Kohlberg assessed moral reasoning -- the justification for a decision, not the decision itself. Two people can make the same choice for different stage-level reasons.
• "Piaget's formal operational stage is universal and reached by all adults." Many adults do not consistently reason at the formal operational level, and formal operational thought emerges only in domains where individuals have experience and education.
• "The five stages of grief always occur in order." Kubler-Ross's stages are descriptive, not prescriptive or linear. Grief trajectories vary widely; some people skip stages or experience them in different orders.

Quick review

• Prenatal: Germinal (0-2 weeks, implantation), Embryonic (2-8 weeks, organogenesis, max teratogen vulnerability), Fetal (9 weeks-birth, growth). Newborn reflexes: rooting, sucking, Moro, Babinski.
• Attachment: Bowlby (biological basis), Ainsworth Strange Situation -- Secure (65%, distressed-separation, comforted-reunion), Avoidant (20%, indifferent), Ambivalent/Resistant (10-15%, intense distress, ambivalent reunion), Disorganized (5%, contradictory behaviors). Harlow: contact comfort over feeding.
• Piaget: Sensorimotor (0-2, object permanence), Preoperational (2-7, egocentrism, no conservation, animism), Concrete operational (7-11, conservation, logical about concrete), Formal operational (11+, abstract/hypothetical reasoning).
• Erikson: Trust vs mistrust (0-1), Autonomy vs shame/doubt (1-3), Initiative vs guilt (3-6), Industry vs inferiority (6-12), Identity vs role confusion (12-18), Intimacy vs isolation (young adult), Generativity vs stagnation (middle adult), Integrity vs despair (late adult).
• Kohlberg: Preconventional (Stage 1: punishment, Stage 2: self-interest), Conventional (Stage 3: approval, Stage 4: law and order), Postconventional (Stage 5: social contract, Stage 6: universal principles). Gilligan: care-based morality critique.
• Adolescence: Puberty (primary/secondary sex characteristics), prefrontal maturation lags behind limbic, Identity vs role confusion, Marcia identity statuses (achievement, moratorium, foreclosure, diffusion), imaginary audience, personal fable.
• Aging: Crystallized intelligence stable, fluid intelligence declines. Socioemotional selectivity: prioritize emotionally meaningful goals. Integrity vs despair. Kubler-Ross stages (DABDA) -- descriptive, not linear.