twin and adoption studies Flashcards
is it scientific
not as scientific as scanning methods as you cant control all variables
what do twin and adoption studies look into
characteristics that are mainly genetically controlled want to understand how genes influence behaviour
how similar are identical twins (MZ)
100%
how similar are non identical twins (DZ)
50%
what is epigenetic modification
how different environmental influences which genes are switched on and off
how can you use twin studies to look into similarities
if relatives have a higher than average risk of getting the disorder themselves then it may be that the disorder has a genetic component but families typically share the same environment so could be a factor
what are concordance rate
probability of one twin having the disorder if the other already has it
expressed as a %
what two situations does research look at
- reared together
- reared apart
what did GOTTESMAN test
concordance rates for schizophrenia
MZ had much higher concordance (48%) than DZ (17%)
partly down to genes however if it was all due to genes concordance would be 100% so other factors are affecting it
what is an issue with testing twins who are reared together
they have the same environment and may be treated similarly so cannot tell what is due to genes and what is due to environment
strengths of using twin studies
- no other way of studying genetic influences clearly because only twins have 100% DNA in common
- MZ + DZ share environment and so there is a natural control over environmental effects
weaknesses of using twin studies
- MZ may have a more similar environment than DZ as identical twins may be treated in a more similar way
- most people are not twins. the findings of twin studies do not necessarily generalise to the general population
how can we use adoption studies
most direct way to isolate genes from environment is adoption as genes come from the biological parents, environment comes from adopted parents
any similarity between child and biological parents suggests a role for genes
any similarity between child and adopted parents suggests a role for the environment
what did CARDORET look at
looked at 126 adopted children, 8 of which were born to a biological parent with manic depression but adopted to a healthy couple
3/8 developed a mood disorder
compared to 8/118 of the others
suggests nature over nurture for depression
strengths of using adoption studies
- provide us with the most direct comparison of nature and nurture as they isolate the influences of genes
- investigate a range of variables and used varied samples and methods including trans-racial adoptions
