Final answer:
Twin studies, adoption studies, and family studies are 3 kinds of studies used to determine the role of heredity and environment in determining psychological characteristics.
Step-by-step explanation:
The 3 kinds of studies commonly used to determine the role of heredity and environment in determining psychological characteristics are twin studies, adoption studies, and family studies.
In twin studies, researchers compare identical twins, who share the same genes, with fraternal twins, who share only half of their genes. By comparing the similarities and differences in personality traits between these two types of twins, researchers can determine the influence of genetics and environment.
In adoption studies, researchers compare the similarities between adopted children and their biological parents, who share genes but not environment, with the similarities between adopted children and their adoptive parents, who share environment but not genes. This allows researchers to separate genetic influences from environmental influences.
In family studies, researchers study the similarities in personality traits among family members, who share genes and environment. This helps to understand the combined effect of genetics and environment.