Twin studies

Twin studies reveal the absolute and relative importance of environmental and genetic influences on individuals in a sample. Twin research is considered a key tool in behavioral genetics and in content fields, from biology to psychology. Twin studies are part of the methods used in behavior genetics, which includes all data that are genetically informative – siblings, adoptees, pedigree data etc.

Twins are a valuable source for observation because they allow the study of varying family environments (across pairs) and widely differing genetic makeup: "identical" or monozygotic (MZ) twins, share nearly 100% of their genes, which means that most differences between the twins (such as height, susceptibility to boredom, intelligence, depression, etc.) is due to experiences that one twin has but not the other twin. "Fraternal" or dizygotic (DZ) twins share only about 50% of their genes. Thus powerful tests of the effects of genes can be made. Twins share many aspects of their environment (e.g., uterine environment, parenting style, education, wealth, culture, community) by virtue of being born in the same time and place. The presence of a given genetic trait in only one member of a pair of identical twins (called discordance) provides a powerful window into environmental effects.

The following 15 pages are in this category, out of 15 total. This list may not reflect recent changes (learn more).

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