Twin Studies Flashcards
Why are twin studies used?
To see if behaviours are shared by those who are genetically similar
What do psychologists look at when they study twins?
The concordance rates meaning the likelihood that if one twin has a certain trait, the other twin will have the same trait
What are monozygotic twins? (identical)
they develop from the same egg and are therefore genetically identical and have 100% of the genes in common
What are dizygotic twins? (fraternal)
they are two babies who share the same womb at the same time but develop from two separate eggs, they share 50% of the same genes like any siblings
If MZ concordance is significantly higher than DZ concordance then
the disorder has genetic componant
If MZ concordance is same or similar to DZ concordance then
the disorder is envrionmentally caused
If MZ concordance is 100% then
the disorder is genetically caused
If MZ concordance is signifcantly less than 100% then
the disorder has an environmental componant
Twin studies are experiments which compare the similarity of behaviour between MZ and DZ twins that have been
brought up together
Epigenetic modification is when
MZ twins become less identical over time due to the environment
Reared apart studies compare the similarity of identical twins who have
grown up together in the same family and those who have grown up in different environments
If those who have grown up apart share characteristsics, it can be
more certaintly claimed that those characteristics have a genetic basis
In adoption studies, similarities between the participanrt and their biological parent suggest genetic componants whereas
similarities between the participant and their adoptive parents would suggest a role for the environment
A weakness of adoption studies is that children are often placed with families similar to their own, therefore,
environmental factors might not be so very different from those of their biological families
A weakness of twin studies is that most people are not twins so results of twin studies may not be representative of the development of non twins, therefore
the findings may not generalise to the development of other children or adults
In adoption studies, developmental trends can be studied because the studies tend to be longitudinal since ppts can be followed as they develop meaning
characteristics that come about as genes are triggered can be studied (E.g schizophrenia) and linked to genetic factors
The usefulness of data from twin studies depends of the instruments used to collect data, e.g
personality/IQ tests which often have questionnable validity and reliability
Due to the adoption process, only certain types of people can adopt which means that the environment may not be as different and
many adopted children are brought up in the same way, so environmental factors may affect the results
A strength of twin studies is that both twins share the same environment which
acts as a natural form of control over the effects it might have
Twin studies are
the main way of studying the effects of genes in behaviour as there is no other way of having identical DNA
It is rare for a child to be adopted by a family immediately from birth, so an adoptee may have spent time living with their biological family, before the adoption took pace or
could have spent time in foster care meaning there are possible confounding variables affecting the findings
Most people are not adopted meaning that those that are adopted are not representative of the whole population and
there may be something different about mothers or babies that led to the adoptions which could have affected the results
Nature refers to
biological causes for behaviour
Nurture refers to
the environmental causes of behaviour: this means the importance of upbringing, regardless of who the parents are
Adoption studies look at the impact of nurture
on children who are raised by parents who are not their biological parents
