Psychology: Methodology: Adoption Studies & Evaluation
Adoption studies are carried out because the environment of adopted children is not the same as that of their biological families, yet they still have genes in common with them!
If, for example, we want to find out whether children of a parent with schizophrenia are more likely to also develop it, we have an issue in that children usually share both genes and environment with their biological parents. If we study children who have a parent with schizophrenia and compare them with children without a parents with schizophrenia and choose all adopted children, the issue of environment is controlled, as adopted children do not share their environment with their biological families, so if there are similarities they are likely to be due to genetic factors.
Researchers have found higher instances of schizophrenia in adopted children whose biological mothers had schizophrenia than among adopted children with no family history.
It is possible, however, that the adoptive families are matched so closely to the biological ones that the environments are not significantly different after all.
Obviously they don't just look at schizophrenia, but it's a useful example to use to illustrate how they work!
They allow separation of genes and environment, keeping the genetic link whilst controlling the environment, so similarities can't be from environmental or learning factors! They remove the issue of environment.
Developmental trends can be studied, because they can be longitudinal. The same group can be followed as they develop, so characteristics which rely on genes being triggered can be studied. Trends can be found and linked to genetic influences.
The environment may not be as different as first thought, as adoption is an official process and only certain types of people can adopt. This might mean that all adopted children are brought up in a similar way, so environmental could affect findings.
Children requiring adoption are placed with families similar to their own, so adopted children are brought up in similar environments to that of the biological family, so environmental factors could still affect the findings.
