twin and adoption study Flashcards
what did Gottesman and shields do
compared Mz and Dz twins for schizophrenia
compared blood groups, finger prints and facial alikeness
obtain medical history from questionnaires and interviews with parents
personality test
concordance rate MZ = 42% and DZ = 9%
genetic component
nature of nurture
must be some environmnetal element as MZ not 100%
evaluate twin studies
+ main way of studing effect of genes on behaviour
+ both twins share same environment, form of conrol
- MZ twins may share same environment more than DZ as they are treated more the same, could explain higher concordance, reduce validity
- most people arent twins, not reperesentative, generalise
+ generate large volume of data, reliable
+ info taken from twin register, contain info about many variables, samples have the ability to be large and representative
+ good starting point
- usefullness depends of instruments used
what are reared apart twin studies
MZ twins separated and brought up in different environments causing characteristic differences
evaluate reapered apart twin studies
+ environmental conditions controlled, similar characteristics is due to identical DNA
+ controlling for genetic differences, identical DNA and two different environments
- not many MZ twin reared apart
- one of the twins may be brought up by different member of same family
- may experience similar environment during separation
what are adoption studies
same genes with biological parents, same environment as adoptive parents
evaluate adoption studies
+ way of separating genes from environment
- environment may not be as different, only certain types of people adopt
- people who adopt are unusual so unrepresentative, well educated, lower mental illness
- most people not adopted
+ useful in showing twin studies often over estimate genetic factors
+ developmental trends can be studies becuase studies are longitudinal
- rare for child to be adopted by family immediatley from birth so have spent time with biological parents
what is the aim of heston
test genetic contribution to SZ by comparing group of adults born to Sz mothers ehre mother and child permanently separated after first 2 weeks after birth
what is the method of heston
had to appear as normal children
mother had to have diagnosis of Sz, thinking disorder, negative for syphilis and separated at birth
58 ppts matched on sex, type of placement and length of time on child care
psychiatric review conducted to see a diagnosis of Sz, records examined, standaridied interviews, Iq test
what was hestons results
10.6% of experimental group developed SZ
0% of control group
later in life 16.6% would develop Sz
what were the conclusions of heston
genetic cause
the lifetime risk of 16.6 was consistent with other findings
other factors shouldnt be ignored
evaluate heston
+ large sample size
+ inter rater reliablitity, 2 psychiatrists and heston analysis
+ ethical, not deliberately separated, 4 ppts withdrew
- most not apoted
- children normally go to similar families, cofounding variables
- american ppts, ethnocentric
