biological explantions - genetic Flashcards
twin and adoption studies
Christiansen studied over 3500 twin pairs in denmark
found concordance rates for offender behaviour of 35% for identical (MZ) males and 13% for non identical (DZ) males with slightly lower rates for females
offender bahviour was checed agaiabst danish police records
this data indicates that it is not just the behavour that might be inherited but the underlying predispoding traits
Crowe foudn that adopted children whose biological mother has a criminal record had a 50% risk of having criminal record by the age of 18
whereas adopted children whose bioloigcal mother didnt have a criminal recrd only had a 5% risk
candidate genes
gentic analysis fo almost 800 finnish offenders by Tiihonen et al
suggest thst two genes - MAOA and CDH13 may be associated with violent crime
MAOA - regulates serotonon in the brian and has been linked to aggressibe behaviour
CDH13 - linked to substance abuse and attention deficit hyperactivity disorder
about 5-10% of all severe violent crime in finland is attributsble to the MAOA and CDH13 genotypes
diathesis- stress model
if genetics do have soem inflcune on offending it seems likely that this is at least partly moderated by the effects of the envrionment
a tendency towards offending behaviour may coem about through the combination of genetic predispostion and biological or psychological triggers
exmaple - raised in a dsyfucntional envrioment or having criminal role models
limitation
issues with twin evidence
assumptions of equal envrinments
it is asued by researchers studying tiwn that envuromental factors are held constant becuase they are brought up together and therefore must experce similar enviromentnts
however this shared environment assumption may apply much more to MZ than DZ twins
becuase MZ twins look idnetical people tend to treat them more cimilarly which in turn affects thie rbehaviour
higher concordance rates for MZ in twin studied may simply be beaucse they are treated much more similarly than DZ twins
strength
support fro diathesis- stress
study of 13 000 danish adoptees was conducted by Mednick et al
when neither the biologival nor adoptove parents had convtions the percentage of adoptees that did was 13.5%
this figure rose to 20% when either the biological parents had convtions and 24.% when both adoptove and biological parents ha convtions
shows that gentic inhwritance plays an importnat role in offendign but enviromental inflcne is clearly also importnant privding support for the diathesis stress midel of crime
