5 Development of Human Behaviour · 5.1 Development of human behaviour
5.1.1 Life-span development: heredity, environment, stages, attachment and developmental tasks
Developmental psychology studies how people grow and change from conception to death; change comes from heredity (genotype) interacting with environment to give the visible phenotype, runs through life-span stages up to old age, is helped or harmed by early experience in critical or sensitive periods, is marked by developmental tasks (Havighurst) and, socially, starts with attachment (Bowlby, Ainsworth, Harlow). This note adds to the education notes; it does not repeat them. Growth vs development, principles of development and the basic heredity–environment facts are in EDU-DV-01; childhood stages, play and language in EDU-DV-02; Piaget and Vygotsky in EDU-DV-03; Freud, Erikson and Kohlberg in EDU-DV-04; individual differences and intelligence in EDU-ID-01.
- APPSC Paper I
- Standard level
- 20 min read
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Core facts
- Developmental psychology = the branch that studies how people grow and change across the life span (physical, cognitive, social-emotional). Nature = largely our genetics (heredity); nurture = environment and experience.
- Development (Hurlock) = a progressive series of orderly, coherent changes leading towards maturity.
- Life-span perspective (Paul Baltes): development is lifelong, multidimensional, multidirectional (gains and losses), plastic, contextual (history, culture) and studied by many disciplines.
- Genotype = the genetic make-up a person inherits; phenotype = the observable traits (height, eye colour, intelligence, personality) that result from the genotype and the environment.
- Dominant gene shows its effect when only one copy is present; recessive gene shows only when both copies are recessive. Most psychological traits are polygenic (many genes).
- Heritability = the share of the differences among people in a group that is due to genetic differences (0 to 1). It describes a population, not one individual.
- Twins: monozygotic (identical) come from one fertilised egg and share about 100% of genes; dizygotic (fraternal) come from two eggs and share about 50%, like ordinary siblings.
- Twin study logic: if MZ twins are more alike (higher concordance) than DZ twins on a trait, genes matter for that trait.
- Adoption study logic: compare adopted children with their biological parents (shared genes) and their adoptive parents (shared home). Likeness to biological parents points to heredity; likeness to adoptive parents points to environment.
- Minnesota Study of Twins Reared Apart (Thomas Bouchard, from 1979): identical twins raised in different homes were still strikingly alike in IQ and personality.
- Life-span stages (NCERT order): prenatal → infancy → childhood → adolescence → adulthood → old age.
- Prenatal sub-stages: germinal (conception to 2 weeks), embryonic (2 to 8 weeks: organs form, most sensitive to harm), foetal (9 weeks to birth). Teratogens = outside agents that harm the unborn child (alcohol, drugs, smoking, infections like rubella, radiation).
- Critical period = a fixed window when an experience must occur for normal development (imprinting, Konrad Lorenz, goslings, 1935). Sensitive period = an optimal but not absolute window (language, attachment).
- Robert J. Havighurst: developmental tasks (Developmental Tasks and Education, 1948); success brings happiness and success with later tasks, failure brings unhappiness, social disapproval and difficulty later. He also used the term teachable moment.
- Attachment = a lasting emotional bond between a child and a caregiver. Attachment theory studies close relationships across the whole lifetime.
- John Bowlby (British psychiatrist): father of attachment theory; Attachment and Loss, Vol. 1, 1969; maternal deprivation hypothesis (WHO report Maternal Care and Mental Health, 1951); study of 44 juvenile thieves (1944).
- Mary Ainsworth: Strange Situation test (Patterns of Attachment, 1978); types secure, insecure-avoidant, insecure-resistant (ambivalent); disorganised was added later by Main and Solomon.
- Harry Harlow: infant rhesus monkeys preferred a soft cloth mother to a wire mother that gave milk; attachment rests on contact comfort, not feeding (The Nature of Love, 1958).
Explained
1. Genotype, phenotype and how genes act
| Term | Meaning | Example |
|---|---|---|
| Genotype | inherited set of genes | genes for tallness |
| Phenotype | what is seen | actual adult height |
| Polygenic trait | many genes add up | intelligence, height |
| Heritability | share of group differences due to genes | about 0.5 for IQ in many studies |
The same genotype can give different phenotypes: a child with genes for tallness stays short if badly fed. Genes set a range, and environment decides where in the range a person ends up.
2. Twin and adoption methods
| Method | Compares | Points to heredity if | Weakness |
|---|---|---|---|
| Twin study | MZ vs DZ twins | MZ more alike than DZ | MZ twins are also treated more alike |
| Twins reared apart | MZ twins in different homes | they stay alike | homes are often similar |
| Adoption study | child vs biological and adoptive parents | child resembles biological parents | selective placement, prenatal effects |
| Family study | relatives of different closeness | likeness rises with shared genes | families share homes too |
The usual findings: IQ, temperament and the risk of some mental disorders (schizophrenia, bipolar disorder) show clear genetic influence; language, religion, values and most attitudes come mainly from the environment.
3. Interaction, not addition. Genes and environment work together:
- Reaction range (Irving Gottesman): genes fix the upper and lower limits; environment decides the point reached.
- Canalisation (C.H. Waddington): some traits (walking, babbling) are so strongly guided by genes that only extreme environments can change them.
- Gene–environment correlation (Sandra Scarr and Kathleen McCartney, 1983): passive (parents give both genes and a matching home), evocative (a child's traits draw certain responses from others), active or niche-picking (older children seek settings that suit their genes).
- Epigenetics: experiences such as stress or poor nutrition can switch genes on or off without changing the genes themselves.
4. Life-span stages to old age
| Stage | Approximate age | Key changes |
|---|---|---|
| Prenatal | conception to birth | germinal, embryonic, foetal; teratogens |
| Infancy | birth to 2 | reflexes, motor milestones, attachment |
| Early childhood | 2 to 6 | language, play, self-control, gender roles |
| Middle and late childhood | 6 to 12 | school skills, peers, logical thinking |
| Adolescence | 12 to 18–20 | puberty, identity, abstract thinking |
| Early adulthood | 20 to 40 | career, intimacy, marriage, parenthood |
| Middle adulthood | 40 to 60–65 | generativity, career peak, menopause, empty nest |
| Late adulthood (old age) | 60–65 onwards | retirement, health, loss, life review |
- Hurlock's eleven stages: prenatal, infancy (birth to 2 weeks), babyhood (2 weeks to 2 years), early childhood (2–6), late childhood (6–10/12), puberty (10/12–13/14), early adolescence (13/14–17), late adolescence (17–18), early adulthood (18–40), middle age (40–60), old age (60 onwards).
- Adolescence: growth spurt and puberty; adolescent egocentrism (David Elkind): the imaginary audience (feeling watched by everyone) and the personal fable (feeling unique and invulnerable, which feeds risk-taking, including delinquency); the search for identity (Erikson).
- Adulthood: choosing work and partner, raising children, caring for ageing parents; mid-life review of goals.
- Old age: slower reaction time, weaker senses and memory for new material; fluid intelligence declines but crystallised intelligence (knowledge, vocabulary) holds up or rises; adjustment to retirement, the empty nest, widowhood and illness; social support and activity protect well-being.
- Facing death: Elisabeth Kübler-Ross (On Death and Dying, 1969) described five reactions: denial, anger, bargaining, depression, acceptance. Not everyone goes through all five or in this order.
5. Early experience and critical / sensitive periods
- Imprinting: newly hatched goslings follow the first moving object they see (Lorenz), only within a short period after hatching.
- Vision: David Hubel and Torsten Wiesel showed that a kitten with one eye kept closed in the first months never gained normal vision in that eye (Nobel Prize 1981).
- Language: children cut off from language until late (the case of Genie, found in California in 1970 at age 13) never fully mastered grammar; second-language accents are easier to avoid when learnt early (Lenneberg's critical period, in EDU-DV-01).
- Prenatal: each organ has its own critical period; most damage from teratogens happens in the embryonic stage (weeks 3–8).
- Social: children raised in poor institutions (for example orphanages without a steady caregiver) show delays; those adopted early recover better than those adopted late. Michael Rutter separated deprivation (a bond formed and then broken) from privation (no bond ever formed), the latter being more harmful.
- Application: early screening of hearing and sight, early childhood care (Anganwadi / ICDS), early intervention for disabilities, stable foster or family care instead of long institutional care, and family-based care for children in need of care and protection.
6. Havighurst's developmental tasks. A developmental task arises at about a certain period of life; it comes from three sources: physical maturation (learning to walk), cultural pressure of society (learning to read, behaving as a responsible citizen) and the person's own values and aspirations (choosing a career).
| Period | Age | Examples of tasks |
|---|---|---|
| Infancy and early childhood | 0–6 | walk, take solid food, talk, control elimination, learn sex differences, tell right from wrong |
| Middle childhood | 6–12 | physical skills for games, get along with peers, reading, writing, arithmetic, conscience and values, personal independence |
| Adolescence | 13–18 | mature relations with peers of both sexes, accept one's body, emotional independence from parents, prepare for a career and marriage, socially responsible behaviour, a set of values |
| Early adulthood | 19–30 | select a partner, start a family, rear children, manage a home, start an occupation, civic responsibility |
| Middle age | 30–60 | adult civic and social responsibility, help teenagers become adults, satisfactory career, adjust to physical changes and ageing parents |
| Later maturity | 60+ | adjust to declining strength and health, retirement and lower income, death of spouse, affiliate with one's age group, satisfactory living arrangements |
Use: teaching and counselling are most effective at the teachable moment, when the body is ready, society expects the task and the person wants it.
7. Attachment theory
- Bowlby (ethological view): attachment is an inborn, evolved system that keeps the infant close to the caregiver for safety. Ideas: monotropy (one main attachment figure), a sensitive period in the first two to three years, and an internal working model (the child's mental picture of self and others that guides later relationships).
- Bowlby's phases: pre-attachment (birth to about 6 weeks), attachment in the making (6 weeks to 6–8 months), clear-cut attachment (6–8 months to about 18–24 months: stranger anxiety and separation anxiety appear), formation of a reciprocal relationship (from about 18–24 months).
- 44 juvenile thieves (1944): 14 of the 44 young thieves Bowlby studied showed affectionless psychopathy (no guilt or concern for others), and 12 of those 14 had suffered long early separation from their mothers; among 44 non-delinquent children attending the same clinic, only 2 had such a separation. This is why the topic matters in work with delinquents.
- Ainsworth's Strange Situation: a 12- to 18-month-old child, the mother and a stranger go through eight short episodes (about 3 minutes each) of separation and reunion in an unfamiliar room. Observed: willingness to explore, stranger anxiety, separation distress, behaviour at reunion.
| Type | During separation | At reunion | Caregiver style |
|---|---|---|---|
| Secure (B, about 60–70%) | some distress | seeks comfort, soon settles | sensitive, responsive |
| Insecure-avoidant (A) | little distress | ignores or avoids mother | distant, rejecting |
| Insecure-resistant / ambivalent (C) | very upset | seeks and resists contact (angry) | inconsistent |
| Disorganised (D) | confused | dazed, contradictory | frightening or abused, neglected |
- Harlow's monkeys: baby monkeys fed by the wire mother still spent most time clinging to the cloth mother and ran to it when frightened. This rejected the "cupboard love" (feeding) explanation of attachment. Monkeys reared in total isolation later showed fear, aggression and poor parenting.
- Rudolph Schaffer and Peggy Emerson (Glasgow, 1964): infants attach most strongly to the person who is most responsive, not the one who feeds most, and many form multiple attachments.
8. One-page comparison of the four stage theories
| Approx. age | Piaget (cognitive) | Erikson (psychosocial) | Kohlberg (moral) |
|---|---|---|---|
| 0–1½ | sensorimotor (0–2) | trust vs mistrust | — |
| 1½–3 | sensorimotor ends; preoperational (2–7) begins | autonomy vs shame and doubt | — |
| 3–6 | preoperational | initiative vs guilt | preconventional (to about 9): punishment, then exchange |
| 6–12 | concrete operational (7–11) | industry vs inferiority | preconventional moving to conventional |
| 12–18 | formal operational (11+) | identity vs role confusion | conventional: good-boy/good-girl, law and order |
| 18–40 | formal operational | intimacy vs isolation | conventional; a minority postconventional |
| 40–65 | — | generativity vs stagnation | postconventional (few): social contract, universal principles |
| 65+ | — | ego integrity vs despair | — |
Vygotsky gives no fixed age stages: development comes from social interaction and culture; learning leads development through the zone of proximal development, with scaffolding by a more knowledgeable other; speech moves from social to private to inner speech.
| Theorist | Number of stages | Driving force | Span |
|---|---|---|---|
| Piaget | 4 | the child's own activity, equilibration | to adolescence |
| Vygotsky | none fixed | social interaction, culture, language | whole childhood |
| Kohlberg | 3 levels, 6 stages | cognitive growth, moral conflict | childhood to adulthood |
| Erikson | 8 | psychosocial crisis at each stage | whole life |
Common traps
- ✗ "Phenotype is the genetic make-up." ✓ That is the genotype; the phenotype is the observable trait (genes + environment).
- ✗ "Fraternal twins share all their genes." ✓ Identical (MZ) twins share about 100%; fraternal (DZ) about 50%.
- ✗ "Heritability tells how much of one person's IQ is genetic." ✓ It describes differences within a group, not an individual.
- ✗ "Bowlby devised the Strange Situation." ✓ Ainsworth devised it; Bowlby gave attachment theory.
- ✗ "Harlow showed that attachment comes from feeding." ✓ He showed it comes from contact comfort (cloth mother).
- ✗ "Imprinting was studied by Harlow." ✓ Imprinting = Lorenz (goslings); Harlow = rhesus monkeys.
- ✗ "Developmental tasks were proposed by Erikson." ✓ Havighurst (1948); Erikson gave psychosocial crises.
- ✗ "Generativity vs stagnation belongs to old age." ✓ It is middle adulthood; old age is ego integrity vs despair.
- ✗ "Vygotsky gave four stages." ✓ Piaget gave four stages; Vygotsky gave no fixed stages (ZPD, scaffolding).
- ✗ "Critical and sensitive periods are the same." ✓ A critical period is a strict window; a sensitive period is the best time, but later learning is still possible.
Quick revision
- Genotype = genes; phenotype = genes + environment, the visible trait.
- MZ twins about 100% shared genes, DZ about 50%; twin, twins-reared-apart and adoption studies separate nature and nurture.
- Life-span view: Baltes; lifelong, multidirectional, plastic, contextual.
- Prenatal: germinal 0–2 weeks, embryonic 2–8 weeks (most sensitive), foetal 9 weeks to birth.
- Old age: fluid intelligence falls, crystallised holds; Kübler-Ross: denial, anger, bargaining, depression, acceptance.
- Critical period: Lorenz imprinting; Hubel and Wiesel kittens; Genie and language.
- Havighurst (1948): developmental tasks, six periods, teachable moment.
- Bowlby: attachment theory, monotropy, internal working model, 44 juvenile thieves (1944).
- Ainsworth: Strange Situation; secure, avoidant, resistant; disorganised (Main and Solomon).
- Harlow: cloth mother over wire mother = contact comfort.
Go deeper: Deeper (beyond what APPSC Paper I usually asks)
Deeper Advanced
1. Limits of heritability. A heritability of 0.5 for IQ does not mean half of a person's IQ comes from genes. It is a figure for a population in one environment; if every child got the same environment, heritability would rise because only genes would differ. A highly heritable trait can still change a lot with environment (height has risen over generations with better food; IQ scores rose across the twentieth century, the Flynn effect).
2. Continuity vs discontinuity and stability vs change. Stage theorists (Piaget, Erikson, Kohlberg, Freud) see development as discontinuous: qualitatively different steps. Learning and information-processing theorists see it as continuous: gradual addition of skills. Bowlby and Freud stressed early experience (stability); the life-span view stresses plasticity (change is possible later).
3. Attachment beyond infancy. Cindy Hazan and Phillip Shaver (1987) found adult romantic styles that mirror Ainsworth's types (secure, anxious, avoidant). Cross-cultural Strange Situation studies (Van IJzendoorn and Kroonenberg, 1988) found secure attachment most common everywhere, with more avoidant children in Germany and more resistant children in Japan and Israel, so the test partly reflects culture. Rutter (Maternal Deprivation Reassessed, 1972) argued that the harm Bowlby described comes from discord and lack of any bond, not from separation as such.
4. Use for a probation officer. Early privation, broken attachments and disorganised attachment are risk factors for conduct problems; adolescent egocentrism and peer pressure explain much risk-taking; developmental tasks give a checklist for a social investigation report (schooling, peer relations, independence, work preparation). Strengthening family bonds and providing a stable adult mentor are the practical uses of attachment research.
Practise this topic. Questions on Nature of development, heredity and environment, individual differences and life-span stages, with answers explained.
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