Twin Studies Flashcards
Fraternal twins (dizygotic DZ)
product of two different sperm and egg during the same pregnancy
Identical twins (monozygotic MZ)
product of the same sperm and egg during the same pregnancy
when can twins said to be concordant
if they both develop the condition of interest
what do twin studies have an enriched understanding of
contribution of genetic and environmental factors in human behaviour
concordance rate
the extent to which both twins share the same characteristic
issues with generalisability in twin studies
may not generalise to the broader population - twins are not necessarily representative of all individuals
what is a problem with twin studies often using volunteer sampling
biased sample - volunteers may all share similar characteristics
why are twin studies useful
no other human shares 100% of their concordance rate
no other way to study genetic influences so early
Application of twin studies to real life
help to identify trends in families
e.g. the Bloomburg family who couldn’t stay awake in the evenings
validity issues with twin studies
role of genes may be over emphasised
the reason for higher concordance rates in MZ over DZ twins may be environmental instead of due to genes
why can twin studies be seen as unethical
separated twin studies useful for looking at environmental and genetic factors - unethical as twins are now adopted together
high validity
natural control over environmental factors as twins usually share the same environment - we can be sure that differences in concordance rates are unlikely to be from environmental effects
Gottesman and Shields (1966) - sample
57 twin pairs found from 45,000 psychiatric patients where at least one had a schizophrenia diagnosis
Gottesman and Shields (1966) - findings
where one MZ twin had schizophrenia, co-twin at least 42 times more likely to have it than a person from the general population
same sex DZ twin at least 9 times more likely to have it if co-twin was diagnosed
in severe cases of Schizophrenia, concordance rate for MZ twins between 75-91 percent - strongly suggests some genetic basis for schizophrenia
