Twin method 3-3

Co twin method. It uses twin study method by using one twin as a control subject who does not receive certain stimulus training or changes in the environment and allowed to grow as they would usually grow where as the first twin is given training for change in environment to study changes.

Goldberg 2003 study used to determine if combat ptsd increases other mental disorders. It showed that combat ptsd increases other mental disorders even after controlling for other factors. Therefore it is environmentally influenced character.

Limitations.

Famous studies. 1979 Minnesota twin studies. 4000 twin study in Sweden. 2014 on sexual orientation and IQ.