RM 2: twin and adoption studies (BP)

Question 1

TWIN STUDIES

Strength

Answer 1

I/J - Validity rating from multiple sources were utilised (teacher and peer ratings) if there were large differences, would highlight biases the teachers/peers had against the child.
E - Therefore, provides interrater reliability means measurement of aggression in study was good allows researchers to make valid conclusions about influence genes play an aggression.

Question 2

TWIN STUDIES

Weakness

Answer 2

I - Can’t conclude cause and effect relationship between genes and aggression as purely correlational.
J - Other factors could affect MZ increased concordance rate for aggression e.g. 1 twin might be stereotyped based on others behaviour
E - therefore teacher pair ratings might be influenced by stereotypes regardless of same rating reducing validity of results that physical aggression is genetically predisposed

Question 3

ADOPTION STUDIES

Strengh

Answer 3

**I/J - **Having a matched design eg controlling gender, and length of time in care minimised participant variables that could have affected internal validity of the results,
E - therefore we can be confident that it is the biological inheritance which caused the difference in the 47 participants born to schizophrenic mothers, not environmental factors such as time in care.

Question 4

ADOPTION STUDIES

Weakness

Answer 4

I - Heston (1966) only found a 10.6% concordance rate which does not provide cause and effect conclusions for genetic predisposition and schizophrenia rates for adopted children as there are other variables, such as drug use, that could have influenced the mental health of the children who were adopted away from their birth family.
However not all factors were able to be controlled. For example, the psychiatric status of the father was not checked, so we can’t be sure if this contributed to the participant’s results.