Glossary of terms
Additive genetic influence, the “adding up” of genes to influence behaviour
Aetiological influences, genetic and environmental influences underlying a phenotype/disease
Aetiology, the causes of a phenotype/disease
Broad-sense heritability, the sum of all genetic effects – additive and dominant
Dizygotic twins, non-identical twins
Dominance genetic influence, the “interaction” of genes at a particular locus which influence behaviour
Monozygotic twins, identical twins
Narrow-sense heritability, sum of all additive genetic influences
Nonshared environmental influence, environmental factors unique to each family member which account for their dissimilarity
Nosology, the classification of diseases
Quantitative genetics, the branch of behavioural genetics focussed on understanding the aetiology of numerous phenotypes using statistical methods and a special study design – e.g., family studies or twin studies
Shared environmental influence, family-wide environmental influences which act to make family members similar