Summarize research findings on the role of genetics and environment in the development of psychological disorders.

Research in behaviour genetics demonstrates that personality traits and psychological disorders stem from both biological and environmental influences. Intelligence and personality serve as common examples studied through family genetic research, twin studies, and adoption analyses.

Genetic Factors

Scientists examine family relationships where "children share 50% of the genes, while twins share 100% of their genes." Twin studies help disentangle genetic from environmental effects by comparing identical (monozygotic) and fraternal (dizygotic) twins.

Environmental Factors

Environmental components split into:

• Shared environment: Experiences common to siblings raised together
• Non-shared environment: Unique experiences specific to each individual

Key Findings

Psychological characteristics result from complex gene-environment interactions rather than single genes. The evidence shows both genetics and environment function together synergistically in shaping personality and behaviour. However, shared environmental factors appear less significant than individual environmental experiences and genetic predisposition in determining psychological outcomes.