Theories and Methods of Development

This is Unit One, part one, on what lifespan development studies and the questions it asks. Unit One opens with a definition: the scientific study of growth, change and stability from conception to death. Carry one question through this part: how much can experience change a developing person, and when does it matter most? Most of these entries circle it. Near the end of the part, the field answers with a distinction between two kinds of window. By the end you will be able to define lifespan development and its three key words. To tell continuous from discontinuous change, and say what a stage theory claims. To explain what a heritability estimate can and cannot tell you, and name the three routes linking genes and environments. To tell a critical period from a sensitive one. And to name Freud's five stages and the three parts of his model of the mind.

Three entries: what psychology studies, when it became a science, and the branch this course belongs to.

First, what psychology is the study of.

HGD 0001 Psychology Defined

Psychology is the scientific study of the mind and of the behaviour it produces, from observable actions to the thinking behind them. Behaviour means observable action. The field also studies affect, a person's emotional experience, including reading other people's emotions, and cognition, every kind of thinking, from memory and calculation to imagination and language.

When psychology became a science, and when it began.

HGD 0002 Wundt Founds a Science

Psychology is dated as a science from eighteen seventy-nine, when Wilhelm Wundt founded it as a scientific discipline in Germany. One date and one founder. The questions themselves are far older. Ancient Greek thinkers, Socrates, Plato and Aristotle, were asking about development around four hundred BCE. The science is young; the questions are not.

The branch of psychology this course is about.

HGD 0003 Lifespan Development

Lifespan development, also called developmental psychology, is the scientific study of growth, change and stability from conception to death. The field's own shorthand is from womb to tomb, every age included. Human development names the wider field, which draws on anthropology, medicine, history, economics and law as well as psychology.

Five entries on the definition's three key words, one early case study, and the domains the field tracks.

The first two words: growth and change.

HGD 0004 Growth and Change

Growth in development usually means maturation, most often biological, such as height, weight and puberty, but also psychological, such as vocabulary. A child's vocabulary and social skills expand year by year alongside their height. Change is not a straight line. It is non-linear, and it can run in either direction across a life.

The third word, stability.

HGD 0005 Stability

Stability is the absence of pronounced change: characteristics that stay the same, or work similarly, across long stretches of life. Picture a shy toddler who grows into a quiet, socially inhibited adult decades later. Temperament and personality account for much of that stability, which is why later units return to both.

One of the field's earliest case studies.

HGD 0006 Victor of Aveyron

Jean-Marc Gaspard Itard, a French physician, wrote a case study of Victor, the Wild Boy of Aveyron, who grew up without human contact. One boy, found living apart from people, was observed and described in great detail. Itard published in eighteen oh two, nearly a century before the child study movement of the eighteen nineties.

Why the field wants its findings put to use.

HGD 0007 Science Put to Use

Application is the goal of turning developmental evidence into practical solutions, such as laws and programmes built on what research shows. One example is a limit on how many non-family teenage passengers a teen driver may carry. The rule rests on research showing that teenagers' risk-taking and reward-seeking are strongly swayed by their peers.

The areas of life that development spans.

HGD 0008 The Domains of Development

Development is studied in five domains: biological, cognitive, social, emotional and personality, tracked across every life stage. This course pairs them, body and mind, then self and others, for each stage. Social, emotional and personality development together are sometimes called psychosocial development, the word Erikson's theory is named for.

Two entries on the field's first great question: does development move gradually, or in steps?

Two ways that change can unfold.

HGD 0009 Continuous and Discontinuous Change

Continuous development is gradual, day-by-day progress. Discontinuous development is a change in kind that does not follow directly from what came before. Vocabulary grows word by word, then two-word phrases give way, seemingly overnight, to sentences. One change can show both patterns: puberty looks sudden, yet the hormonal preparation behind it is continuous.

The theories built on discontinuity.

HGD 0010 Stage Theories

Stage theories, such as Piaget's and Erikson's, describe development as brief bursts of rapid change between long stretches of stability. Picture a staircase: long flat landings joined by short, steep climbs. Development is also assumed to be progressive, so moving back to earlier forms, called regression, can signal that something is wrong.

Five entries on the field's oldest debate, and on how genes and environments work together.

The oldest debate, and the misconception inside it.

HGD 0011 Nature and Nurture

Nature and nurture both shape almost every human characteristic, genes and environment together, in proportions that vary from one trait to another. The timing of puberty is one example; genes and nutrition both help to trigger it. The misconception is nature or nurture, as if one must win. The field now asks how the two combine for each trait.

How researchers measure the genetic share.

HGD 0012 Heritability Estimates

A heritability estimate is the extent to which genetic differences explain differences in a trait across a group of people. It splits the differences across many people into genetic and environmental shares. It says nothing about one person. A heritability estimate never tells you how much of your own trait comes from your genes.

The limits that genes may set.

HGD 0013 Reaction Range

Reaction range is the idea that genes set upper and lower limits for a trait, and environment decides where within that range a person lands. Picture two children with the same genetic range, one raised with rich stimulation, one without. Applied to intelligence, the idea remains largely theoretical, because researchers cannot ethically manipulate how children are raised.

Three routes by which genes shape environments.

HGD 0014 Gene–Environment Correlation

Gene–environment correlation means that people's genes help shape the environments they experience, so the two cannot be treated as independent. One reading child shows all three types. In passive correlation, parents pass on both genes and a home: parents who love reading give her their genes and a house full of books. In evocative correlation, her inherited traits draw responses from others, and her constant reading prompts library trips. In active correlation, she chooses a setting that fits her tendencies, and joins a book club. So a home full of books may reflect the parents' genes, which the child shares, as much as the books themselves. Separating nature from nurture takes designs that pull the two apart.

How environment changes the way genes work.

HGD 0015 Epigenetics

Epigenetics is the study of how environment and behaviour change the way genes are expressed, without changing the genes themselves. Stressful surroundings, for example, can trigger chemical tags on DNA that alter how particular genes are expressed. Research suggests that childhood trauma may sensitise the body's stress-regulating systems through chemical changes of this kind.

Seven entries on what typical development looks like, and on the windows when experience matters most. The opening question is answered here.

What typical development looks like.

HGD 0016 Normative Development

Normative development means the typical or expected outcomes of growth, observed across a wide range of conditions and settings: most children reach the same milestones in very different homes and cultures. Humans are highly adaptable. Good outcomes occur even in poor circumstances, and it takes extreme deprivation, at particular times, to severely restrict development.

The capacity behind that adaptability.

HGD 0017 Resilience

Resilience is the capacity for adapting well in the face of adversity, the definition the American Psychological Association gives. Picture a child meeting serious hardship at home and still reaching the typical milestones. The exam's outline pairs risk and resilience: the hardships that threaten development, and the capacity to meet them.

The first kind of window.

HGD 0018 Critical Periods

A critical period is an age range during which certain experiences are required for an ability to develop at all. If the needed experience is missing at the time, the ability fails to develop normally. The strongest evidence comes from rare cases of extreme deprivation, since the experience cannot ethically be withheld.

One such case of extreme deprivation.

HGD 0019 Genie

Genie was a girl severely neglected and rarely spoken to, rescued in the nineteen seventies at thirteen, well past early childhood. After rescue her comprehension and speech improved, yet her language stayed markedly unlike typical speech, and it was processed in her brain's right hemisphere, not the left. Her case is read as evidence for a critical period.

The gentler kind of window.

HGD 0020 Sensitive Periods

A sensitive period is an age range when a characteristic is especially open to environmental input, so experience then helps but is not required. A coach who times new training to an adolescent athlete's growth spurt is using one. Other examples span the lifespan: youth leaders during adolescent identity work, and life review for older adults in assisted living.

The payoff: the two windows side by side.

HGD 0021 Critical or Sensitive

Critical and sensitive periods both describe windows when experience matters more than usual, but they differ in what happens if the window is missed. In a critical period a particular experience is required; without it the ability does not develop normally, as Genie's case suggests for language. In a sensitive period the right experience is especially helpful, so learning is easier then, but the ability can still develop later. One question sorts every example: if the window is missed, is the ability lost, or only harder to gain? That is the answer to the question this part opened with. The two terms are often used as if they meant the same thing. They do not.

How averages relate to individual children.

HGD 0022 Averages and Individuals

Developmental findings are statistical averages, so an individual who differs from the norm does not invalidate them; sequence and typical window matter most. A toddler producing two-word phrases at twelve months rather than the typical eighteen is one example. Culture shifts timing too: Israeli parents encouraged more tummy time than Dutch parents, and their babies crawled better.

Two entries to close the part, opening the field's theories with Sigmund Freud.

Freud's sequence of psychosexual stages.

HGD 0023 Freud's Psychosexual Stages

Sigmund Freud's psychosexual theory holds that early childhood experiences shape personality as children pass through a sequence of stages: oral, anal, Oedipal, latency and genital. Frustration or overindulgence at a stage was said to cause fixation there, producing a dependent, controlling or competitive personality style.

Freud's model of the mind's structure.

HGD 0024 Id, Ego and Superego

Freud's structural model divides the mind into three interacting parts: the id, seat of drives and instincts; the ego, logical and reality-oriented; and the superego, the conscience. Impulse, reason and conscience each pull on an everyday decision. Personality reflects their balance: a dominant id yields impulsiveness, a dominant superego overcontrol, a dominant ego a balanced style.

Look at what you can now do. You can define lifespan development as the scientific study of growth, change and stability from conception to death, and say that change is non-linear while stability is the absence of pronounced change. You can tell continuous change, gradual and day by day, from discontinuous change, a change in kind, and say that stage theories describe brief bursts between long stretches of stability. You can explain that a heritability estimate describes a group and never one person, and name the passive, evocative and active routes by which genes shape environments. You can tell a critical period, when experience is required, from a sensitive period, when it helps but is not required. And you can name Freud's five stages, oral, anal, Oedipal, latency and genital, and the id, ego and superego. Part two opens with how the ego manages anxiety.