twin studys Flashcards
Twin Studys
A way to investigate genes and if they cause behaviors
this is done by comparing the behaviours between DZ twins and behaviour between MZ twins to find any differences in the behaviour that is being studdyed
Normal methord in twin studdys
Comparison between MZ and DZ twins behaviours that have grown up in the same environments to the other twins
Seperated Twins
Compare the similarities and differences of MZ twins behaviours that have grown up together in the same family to those in different environments
If those who have grown up together a more alike than those grown up apart this would then support the role of the environment rather than the role of genes
MZ and DZ (AO1 point 1 for evaluate/ describe q)
MZ twins = 100% geneticaly identical
DZ Twins = 50% Geneticaly Identical
Concordence rate (AO1 point 2 for evaluate/describe q)
If the concordance rate in MZ twins are 100% this would mean that the behavior being studied is a genetic behavior
If there is a higher concordance rate in DZ twins then the behavior would be Environmental
Not 100% concordance rate in MZ twins (AO1 point 3 for evaluate/describe q)
When the concordance rate for MZ twins is still higher than DZ twins but not 100% (80%<= enviroment) there may be other factors affecting the result not just genetics
Enviroments (AO1 point 4 for a evaluate/describe Q)
It is usually assumed that all twins in the study abort up in the same environment to other twins as not to invalidate the results
Example
Brendgen et al 2005
(contempomary study)
quebec newborn twin study
Weakness of Twin Study
(internal validity not 100%MZ CR)
One weakness of using twin studies is but it has low internal validity due to not eliminating extraneous variables of the environment that could have an effect on the results if the concordance rate of MZ twins is not exactly 100%
This would mean the behaviour wouldnt be fully genetic even if the concordance rate was 80% meaning the conclusion would be invalid and therefore has low internal validity
weakness of twin studys
ecological validity seperated twins
In a separated twins twins study it is extremely unlikely to find MZ twins that have grown up in different environments convert for giving it low ecological validity due to it being extremely rare in real life and unethical to artificially create
Strength of twin study
internal validity 100% identical MZ twins
MZ twin share 100% of DNA which means if the concordance rate is also 100% it is guaranteed that’s the behavior being studied is a genetic behavior and this is therefore an objective result meaning this conclusion would have high internal validity due to cause in cause and effect being firmly established
Strength of twin studys
seperated twimd
In separated twin studies if the behavior of the MZ twins is coherent throughout both the MZ twins have grown up in the same environment and MZ twins have grown up in different environments is 100% genetic if there is a difference between them then the behavior is not genetic
This makes the results easily interpretable by researchers and reduces the likelihood of an invalid conclusion and therefore it has high internal validity
What is the Concordance Rate?
a statistical measure
describes the proportion of pairs of individuals that share an attribute
given that one already possesses this trait
For example 100% concordence rate in MZ twins would confirm the attribute they are measuring has a Genetic Cause
