Lifespan Development – Discovering Psychology (Chapter 9)

Lifespan Development – Key Themes

  • Developmental psychology = scientific study of how people change across the entire lifespan.
    • Focuses on changes that are:
    • Physical
    • Cognitive
    • Social
  • Life is usually divided into qualitative stages (abrupt or gradual).
    • May be defined by: age, life-transitions, critical periods.
  • Major stage chart (conception ➔ death):
    • Prenatal (conception→birth)(\text{conception}\rightarrow\text{birth})
    • Infancy & Toddlerhood (birth→2 yrs)(\text{birth}\rightarrow2\,\text{yrs})
    • Early Childhood (2→6 yrs)(2\rightarrow6\,\text{yrs})
    • Middle Childhood (6→12 yrs)(6\rightarrow12\,\text{yrs})
    • Adolescence (12→18 yrs)(12\rightarrow18\,\text{yrs})
    • Emerging Adulthood (18→25 yrs)(18\rightarrow25\,\text{yrs})
    • Young Adulthood (25→40 yrs)(25\rightarrow40\,\text{yrs})
    • Middle Adulthood (40→65 yrs)(40\rightarrow65\,\text{yrs})
    • Late Adulthood (65 yrs→death)(65\,\text{yrs}\rightarrow\text{death})

Genetic Contributions to Development

  • Genotype vs. Phenotype
    • Genotype = 4646 chromosomes ( 2323 pairs) inherited from biological parents.
    • Phenotype = observable traits – produced by gene × environment interaction.
  • Basic biological units
    • Zygote: single cell at conception (egg + sperm).
    • Chromosome: long DNA strand in nucleus.
    • DNA (deoxyribonucleic acid): double helix; chemical basis of heredity.
    • Gene: segment of DNA that encodes a protein – basic unit of heredity.
  • Epigenetics
    • Studies cellular mechanisms regulating gene expression.
    • Expression can be triggered by other genes, internal chemistry, external environment.
    • Critical to understanding genotype–phenotype conversion.

Prenatal Development

  • Overall theme: Single-celled zygote ➔ full-term fetus.
  • Three sub-periods
    1. Germinal / Zygotic 00(–)2 wks2\,\text{wks}
    • Rapid mitosis, implantation in uterine wall.
    1. Embryonic 3→8 wks3\rightarrow8\,\text{wks}
    • Formation of amniotic sac, umbilical cord, placenta.
    • Greatest susceptibility to teratogens (radiation, toxins, infectious agents, drugs, alcohol, maternal stress).
    1. Fetal 9 wks→birth9\,\text{wks}\rightarrow\text{birth}
    • Growth, maturation, functional refinement.
  • Brain development
    • ≈3 wks\approx3\,\text{wks}: fluid-filled neural tube lined with stem cells.
    • Tube top thickens ➔ hindbrain, midbrain, forebrain.
    • Stem cells proliferate ➔ neurons + glia.
    • Synaptic pruning: used connections strengthen, unused eliminated.
    • 6th6^{\text{th}} prenatal month: fetal EEG resembles newborn; sleep–wake cycles appear.
    • At birth: brain ≈25%\approx 25\% adult weight (< 1 lb1\,\text{lb}); postnatal dendritic growth & synaptogenesis.

Infancy & Childhood – Physical and Sensory Foundations

  • Newborn reflexes (survival-oriented, automatic):
    • Rooting (cheek touch ➔ head turn + mouth open)
    • Sucking (oral stimulation ➔ rhythmic suck)
    • Babinski (foot stroke ➔ toe fan/curl)
    • Grasping (finger hold, can lift baby)
    • Stepping (pre-walking leg motions)
  • Sensory capacities
    • Vision: near-sighted, prefer human faces; best focus 6–12 in6\text{–}12\,\text{in}.
    • Hearing: hours after birth prefer mother’s voice.
    • Smell: 22-day-olds prefer mother’s scent.
  • Brain & motor milestones
    • Brain reaches 75%75\% adult weight by end of infancy.
    • Motor skill progression: cephalocaudal (top➔bottom) & proximodistal (center➔limbs).
    • Universal sequence but variable timing (see milestone chart: rolling, sitting, standing, walking, etc.).

Temperament & Early Social Experience

  • Temperament types (Thomas & Chess, 19861986): Easy, Slow-to-warm-up, Difficult – relatively stable.
  • Reactivity (Kagan)
    • High-reactive = intense responses; Low-reactive = calm/bold.
    • Rooted in genetics/biology but molded by environment & culture.
  • Cultural sleeping arrangements
    • U.S.: solitary sleep; Mayan & others: co-sleeping fosters interdependence.
Attachment
  • Harlow’s monkeys: contact comfort > food reinforcement.
  • Ainsworth’s Strange Situation
    • Secure vs. Insecure attachment patterns based on exploration, distress, reunion behaviors.
    • Secure attachment predicts later emotional & relational health; infants may form multiple secure bonds.

Cognitive Development – Piaget’s Theory

  • Children actively construct knowledge via interaction with environment.
  • Four qualitatively distinct stages
    1. Sensorimotor (0→2 yrs)(0\rightarrow2\,\text{yrs})
    • Learning via senses & actions.
    • Lack object permanence until late stage.
    1. Preoperational (2→7 yrs)(2\rightarrow7\,\text{yrs})
    • Symbolic play, language explosion.
    • Limitations: egocentrism, irreversibility, centration, non-conservation (classic liquid task).
    1. Concrete Operational (7→11 yrs)(7\rightarrow11\,\text{yrs})
    • Logical operations on concrete objects; mastery of reversibility, conservation, classification.
    • Still cannot handle abstract/hypothetical reasoning.
    1. Formal Operational (adolescence→adulthood)(\text{adolescence}\rightarrow\text{adulthood})
    • Abstract, hypothetical, scientific thought; depends on domain expertise.
  • Strengths: groundbreaking, spurred research, key insight of qualitative shifts.
  • Critiques: underestimated infants, cultural/ social influences (Vygotsky’s ZPD), overestimated universal attainment of formal operations (info-processing view).

Adolescence – Biological, Cognitive & Social Transition

  • Begins ≈11–12\approx11\text{–}12; ends with adult roles.
  • Puberty
    • Primary sex characteristics: ovaries, uterus, testes, penis mature.
    • Secondary characteristics: breasts, facial hair, voice change.
    • Growth spurt: rapid height/weight.
    • Typical timing table (girls 22 yrs ahead):
    • Menarche ≈12.5\approx12.5, first ovulation 13.513.5.
    • Boys: first ejaculation 1313, voice lowers 1515.
  • Timing factors: genetics, nutrition, body fat, stress, father absence; heavy exercise delays, obesity hastens.
  • Early maturation effects
    • Boys: athletic & popular but higher risk behaviors.
    • Girls: negative body image, higher teen pregnancy risk.
  • Transgender youths: puberty may cause distress ➔ possible use of puberty blockers (controversial).
  • Adolescent brain
    • 2nd gray-matter spurt ∼11\sim11–1212 then pruning back-to-front.
    • Limbic hyper-reactivity vs. still-maturing prefrontal cortex ➔ emotionality, impulsivity.
  • Social relations
    • Healthy rise in parent conflict = autonomy development.
    • Peer influence rises; romantic relationships begin ( 25%25\% by 1212, 70%70\% by 1818 ).
Identity – Erikson & Beyond
  • Identity vs. Role Confusion stage: exploration ➔ commitment.
  • Erikson’s pathway: role confusion → moratorium → integrated identity.
  • Other lasting psychosocial stages (trust–mistrust … ego integrity–despair) define adulthood & aging outcomes.
Moral Development – Kohlberg
  • Preconventional (punishment/obedience, mutual benefit)
  • Conventional (interpersonal expectations, law & order)
  • Postconventional (legal principles, universal ethics)
  • Critiques: reasoning ≠ behavior; cultural & gender debates (Gilligan’s care ethic – mixed evidence).

Adulthood – Emerging, Young, Middle

  • Emerging adulthood (late\,teens\rightarrowlate\,20s)
    • Exploration & instability before full adult commitments.
    • Exists mainly in industrialized societies.
    • Median age at first U.S. marriage ∼30\sim30 men, ∼28\sim28 women – risen steadily since 19601960.
  • Physical trends
    • Peak strength 2020s–3030s; gradual decline midlife; accelerated decline late life.
    • Influenced by genes + lifestyle (epigenetic interaction).
  • Reproductive hormones
    • Menopause (late 3030s–early 5050s): end of menstruation & fertility.
    • Andropause: gradual testosterone drop; erectile, libido changes.
  • Social roles
    • Diverse marriage/cohabitation patterns; >50\% first marriages end in divorce.
    • Parenthood transition: temporary dip in marital satisfaction; rises after “empty nest.”
    • Dual-career dynamics; fathers more involved but mothers still primary caregivers in hetero couples.

Late Adulthood – Aging Well

  • Life expectancy U.S.: men 7373, women 7979 (mean).
  • Majority remain healthy & self-sufficient.
  • Cognitive aging
    • Stability until ≈60\approx60; vocabulary stable till ≈90\approx90.
    • Decline areas: memory, perceptual speed, verbal fluency; accelerated under chronic stress & low stimulation.
  • Protective factors
    • Aerobic exercise = neuroprotective; 11-year walking program ↑ hippocampal volume 2%2\% vs. 1.5%1.5\% decline in stretching controls.
    • Education, mental engagement, rich social life.
  • Activity theory of aging: life satisfaction highest when continuing or replacing previous activities.
    • Achieve ego integrity (life review satisfaction) vs. despair (regret).
Death & Dying
  • Attitudes shaped by culture/religion; worry peaks midlife then drops.
  • Kübler-Ross stages: denial, anger, bargaining, depression, acceptance – not universal, order varies.

Parenting Styles & Raising Healthy Children

  • Authoritarian: high demand, low warmth – obedience, possible low self-esteem.
  • Permissive: high warmth, low control.
    • Permissive-indifferent = low warmth & control.
  • Authoritative: high warmth + reasonable control – linked to higher grades, confidence.
    • Practical guidelines: show love, listen, inductive discipline, tailor to temperament & cognition, avoid perfectionism.

Ethical & Practical Implications

  • Honors gene–environment interplay: interventions (education, parenting, exercise) can offset biological risks.
  • Public health: awareness of teratogens, adolescent risk behaviors; support for transgender youth.
  • Policy: maternity/paternity leave, elder exercise programs, school curricula on moral reasoning.