Nature vs nurture

• Studies on relatives, twins and animals have contributed to our knowledge.
• People are born to be the way they are due to genetic factors (genetic determinism), while others argue that people are raised to be the way they are due to environmental factors (environmentalism).
• The Nature-nurture continuum refers to the idea that both genetic and environmental factors contribute to individual differences.
• Phenotype: observable and measurable characteristics of an individual.
• Genotype: genetic composition of an individual.
• Genetic variant refers to the contribution of different versions of the human genome to individual differences.
• Alleles are genes for the same characteristic.
• Dominant and recessive alleles.
• Both genetic and environmental hypotheses predict similarity between relatives who live together.
• Familial resemblance: assessing resemblance between relatives whose relatedness is known.
• Family resemblance: assessing resemblance between relatives whose relatedness is unknown.
• Correlation in IQ is used to determine components of phenotypic variance.
• Natural experiments are used to study genetic influences, where genetic influences are either controlled or randomised so that the effect of the environment can be studied.
• Environmental influences are controlled so that the effects of genes can be studied.
• Percentage of Genes shared between family members: parent (50%), sibling (50%), twin - identical (100%), twin – non-identical (50%), half-sibling (25%), niece/nephew (25%), aunt/uncle (25%), cousin (12.5%).
• Altricial young are helpless at birth and take time to learn, while precocial young are independent at birth and learn to follow mother, forming a bond of attachment and recognition.
• Individual differences can be explained by a complex interplay between genetic and environmental factors.
• The significance of each of these ways of genetic-environmental interaction changes over the course of development.
• Shared versus non-shared environments: shared – all family share the same environment to the degree that, on average psychosocial environmental characteristics (e.g social class and parenting styles) differ from other families, non-shared – parents no matter how hard they try, do not treat all their children in exactly the same way.
• Niche-picking is the act of actively choosing environments that complement heredity.
• Canalization refers to the tendency of heredity to restrict the development of some characteristics to just one or a few outcomes.
• Genetic-environmental correlation refers to the idea that heredity influences the environment to which individuals are exposed.
• Animal studies can inform us about the development of behaviour in shared and non-shared environments, instinct, maturation, and learning.
• Parental investment involves helping offspring in providing warmth and shelter, food, transport and protection from predators.
• Genes can shape and interact with the environment in three ways: Passive effects, evocative relationship, and active way.
• Genes are probabilistic not deterministic, they code for proteins, not behaviours, and genotype-phenotype correspondence is not perfect.
• Imprinting was advanced by Lorenz in the 1930s, with two major ideas: Imprinting is the result of an instinct, and the "critical period" during which imprinting can occur is limited and severely restricted to the animals very early life.
• Bird song is a good example of how genes can shape and interact with the environment, with some species having a characteristic song, and others not.
• Genes do not fix behaviour in a rigid fashion but establish a range of possibilities, which then depend on environmental influence.
• Comparing shared and non-shared environment can allow us to understand the contribution of genes and environment.
• Heritability: The proportion of phenotypic variance that can be accounted for by genetic difference among individuals.
• Heritability estimate (h2) – A statistic that measures the extent to which individual differences in complex traits in a specific population are due to genetic factors.
• Kinship studies are used to determine the importance of heredity in complex human characteristics.
• Estimating heritability involves comparing the characteristics of family members to determine the importance of heredity in complex human characteristics.
• Population A: Very Variable Environment, e.g different countries, may have lower h2 than in Population B.
• Population B: Very Uniform Environment, e.g same classroom, may have higher h2.
• Each person’s unique genetically determined response to a range of environmental conditions is referred to as the range of reaction.
• Geneticists compare identical twins reared apart or comparing adopted vs nonadopted.
• MZ twins share 100% genetic material and if raised apart AND were still rated as being similar, then this could provide strong genetic evidence.
• Twin studies are used to study the influence of genes on behaviour, as siblings share genes (50%) and twins provide a special example of genetic similarity (100% versus 50%).