Factors Influencing Development
Heredity and environment
Heredity provides genotype and potential; environment provides expression. Reaction range, canalisation, gene-environment correlation and epigenetics matter. Nature and nurture interact; they are not additive opposites. Temperament interacts with caregiving: a good fit supports adjustment, a poor fit creates stress.
Family, socio-economic and cultural factors
Family structure, parenting style, stimulation, nutrition and health shape outcomes. Authoritative, authoritarian, permissive and uninvolved styles describe differing warmth and control. Socio-economic status affects resources, stress, schooling and health care; poverty operates through food insecurity, crowded housing, chronic stress and unequal school quality. Culture shapes expectations, language, gender roles and child-rearing practices.
Nutrition and health
Protein-energy malnutrition, iron deficiency anaemia, iodine deficiency and repeated infections affect growth and cognition. Immunisation, safe water, sanitation and antenatal care are protective. Health and nutrition effects are cumulative and often reversible with timely intervention.
Worked example
Two children have similar scores at age 6, but one lives in a deprived household. Reasoning: you cannot conclude heredity is stronger because environment has been restricted; the reaction range has not been expressed. Look for cumulative risk and protective factors, not a single-cause answer.
Traps
Do not say heredity sets a fixed ceiling; do not call socio-economic status a cultural factor; do not confuse correlation with causation; do not ignore bidirectional effects, because the child also affects the family.