3.2 Human development

Brain development is the maturation and reorganisation of neural systems across childhood and adolescence. Growth in connectivity and executive control can change what a person can learn or regulate, but development is not a single timetable.

Genes, nutrition, stress, sleep and social experience interact with maturation. A developmental difference may reflect timing, opportunity or measurement rather than a fixed ability or a simple biological cause.

A teenager may improve planning as fronto-parietal networks mature, while practice and school demands also shape the skill. The same age range contains large individual variation, so averages are not a destiny.

Maturation is not the same as inevitability. Separate biological change, experience, task demands and the evidence used to infer a mechanism.

A critical period is a narrow developmental window in which particular input is required for typical development; a sensitive period is a time of heightened responsiveness when later learning may still occur. Neuroplasticity allows experience to strengthen, weaken or reorganize neural connections within biological constraints. Evidence of poorer outcomes after late input supports a timing effect only when deprivation, opportunity, recovery and alternative explanations are also considered.

Sociocultural factors are the language, practices, relationships, institutions and norms through which people learn. They shape which skills are valued, which strategies are available and how behaviour is interpreted.

Cross-cultural differences can reflect different activities and expectations rather than different basic capacity. Compare tasks fairly, ask whose knowledge defines success, and avoid treating one schooling style as a universal baseline.

A child who learns mental arithmetic through market transactions may use strategies that a classroom test does not reward. The context changes the practice and the measurement, not necessarily the underlying potential.

Culture is not a single national label and sociocultural explanation does not deny biology. Identify the practice or institution that supplies the learning opportunity.

A stage theory proposes qualitatively distinct forms of thinking or behaviour that emerge in an ordered sequence; a continuous model proposes gradual, quantitative change as processes strengthen with maturation and experience. Both organize development, but they predict different patterns of transition.

Piaget's account is a stage theory: changes in cognitive structure are used to explain why children solve classes of problems differently across stages. An information-processing model is continuous: gains in attention, processing speed, strategy use and working memory can accumulate and vary by task. Evaluate each by its mechanisms, predictions, cultural range and evidence for abrupt versus gradual change.

If children improve steadily across several memory tasks, the pattern supports continuous change more than a single abrupt transition. If a coordinated new way of reasoning appears across tasks near the same period, that is more consistent with a stage claim—but practice, task language and schooling must still be ruled out.

A stage is not a rigid age label and continuous change is not simply ‘getting older’. Distinguish competence from task performance, look for within-person transitions, and do not assume one model must explain every domain of development.

Theory of mind is the ability to represent another person's beliefs, intentions, knowledge or feelings, including the possibility that they are mistaken. It supports prediction and communication but is not identical to empathy.

Tasks often test whether a child distinguishes reality from another person's belief. Performance depends on language, executive control, familiarity and task demands, so a failed task does not isolate one missing mental ability.

If a child sees a toy moved while another person is absent, predicting where that person will search tests access to information rather than the child's own knowledge. The mismatch is the key evidence.

Passing a false-belief task does not prove mature social understanding in every setting, and failing it does not prove an absence of all perspective-taking.

Attachment is an enduring relationship that provides security and a base for exploration. Consistent sensitive care can support regulation, while deprivation or disrupted caregiving can increase risk for later difficulties.

Outcomes depend on timing, duration, quality of replacement care, temperament and later relationships. Correlation between early experience and later behaviour cannot by itself establish one pathway or eliminate resilience.

A child separated from a primary caregiver may show distress and later difficulty trusting adults, but stable alternative care and supportive relationships can change the trajectory. Risk is not a sentence.

Attachment is not the same as constant contact and one early event does not determine a person's future. State the mechanism, developmental window and protective factors.

Attachment can contribute to development of self through repeated co-regulation and expectations about whether the self is worthy of care and whether others are available. These internal working expectations can guide emotion regulation and relationships, but they are revisable through later supportive experiences and should not be treated as fixed personality types.

Enculturation is the gradual learning and internalising of a culture's norms. Through family, peers, school, media and institutions, children learn what people like them are expected to value, feel and do, and these expectations become part of self-concept and identity.

Norms are transmitted through modelling, instruction, stories, routines, approval and sanctions. A child may first comply to gain acceptance, then internalise the standard and use it to evaluate the self. The process is active: children interpret, negotiate and sometimes resist competing norms.

A child repeatedly praised for helping younger relatives may learn that responsibility to family is valued and come to describe being dependable as part of who they are. Peers or school may promote different expectations, so the resulting self reflects several social contexts rather than one uniform culture.

Enculturation is not genetic inheritance and a shared norm does not produce identical selves. Identify who transmits the norm, the reinforcement or meaning that supports it, evidence of internalisation, and the possibility of change across contexts.

Peer influence occurs when people of similar age or status shape behaviour, identity or norms. Social identity processes can make group membership meaningful, while comparison supplies standards for belonging and distinction.

Influence can support prosocial behaviour or increase risk, depending on the group norm, status structure, opportunity and the person's need for acceptance. Agency and multiple peer groups prevent a single-pressure explanation.

A new student may adopt a team's training routine to be recognised as a member. If the team rewards unsafe dieting, the same belonging mechanism can produce harm rather than health.

Peer influence is not automatically conformity or coercion. Identify the group, the valued identity, the reward or sanction and whether the person accepted or resisted the norm.

Childhood experiences include caregiving, conflict, trauma, opportunity and social loss. Their effects depend on exposure, interpretation, developmental timing, support and later experiences rather than on the event label alone.

War or chronic threat can affect stress regulation, learning and relationships, but studies must separate direct exposure from displacement, poverty, family disruption and selective survival. Protective relationships can moderate risk.

Two children exposed to the same move may show different outcomes because one has stable schooling and a trusted adult. Comparing only the event without the surrounding pathway hides the mechanism.

An adverse experience is not a diagnosis and resilience is not proof that no harm occurred. State the outcome, time course, alternative exposures and evidence quality.

Observation systematically records behaviour as it occurs. Naturalistic observation preserves context; controlled observation standardises the situation. Structured coding makes observations comparable but can miss unexpected meaning.

Define behaviours operationally, train observers and check inter-observer agreement. Reactivity, observer expectations, sampling time and ethical privacy limits affect validity; covert observation requires a strong justification and safeguards.

To study playground cooperation, code each helping episode, sample the same time windows and compare observers' classifications. The design can show frequency and context, but not automatically the private intention behind an action.

Seeing a behaviour does not prove its cause. Distinguish frequency, interpretation and inference, and report who was observed, when, and under what conditions.

To conduct the practical: define an observable research question; choose naturalistic or controlled, overt or covert, participant or non-participant design; operationalise mutually clear behaviour categories; choose event or time sampling; pilot the coding schedule; obtain consent or justify and safeguard any public observation; train observers and check agreement; record without identifying participants; then summarize patterns and report reactivity, privacy and causal limits.