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P3: forensic psychology
biological explanations for criminality
what do genetic explanations suggest abt offenders?
-offenders inherit a gene or combo of genes which predispose them or
make them more likely to commit a crime
-twin studies used to illustrate this
what did Lange (1930) investigate?
-investigated 13 MZ and DZ twins where one of the twins in each pair
had served time in prison
what did he find?
-10 of the MZ twins and 2 of the DZ twins had a twin who was also in
prison
-concluded that genetics play a predominant role in offending
behaviour
what did Christiansen (1997) study and find?
-studied 87 MZ twins and 147 DZ twins and found a concordance rates
33% in MZ and 12% in DZ= supports the idea that offending may have a
genetic component
what did Tiihonen et al (2014) find?
-revealed abnormalities on 2 genes which may be associated with
violence
-MAOA gene = controls serotonin and dopamine in the brain and has
been linked to aggressive behaviour
-CDH13= linked to substance misuse and ADHD
what does the diathesis-stress model say abt this?
-criminal behaviour may occur due to an individual with a genetic
predisposition to crime encountering an environmental trigger which
P3: forensic psychology 1
, results in them committing crime
explain one strength of the genetic explanation for criminality
P- research to support diathesis-stress model of crime
E- Mednick et al (1984) studied over 13000 danish adoptees where one
conviction was measured as criminal activity.
neither biological or adoptive parents had convictions= 13.5% did
when one of them had convictions= 20% did
when both parents had convictions= 24.5%
E- suggests that although genetic inheritance plays an important role in
offending environmental influence cant be ignored
L= increases reliability
explain one limitation of the genetic explanation for criminality
P- problems with twin studies
E- they are poorly controlled such as Lange’s research and judgements
related to zygosity were based on appearance rather then DNA testing
so may lack validity
E- cant accurately measure concordance rates + DZ twins may look
similar and be assumed to be MZ twins by appearance which inflates
concordance for MZ twin
D- most twins reared in same environment = confounding variable as
MZ twins look similar they may be treated similarly so internal validity is
compromised because they may be measuring the effect of
environment (how they are treated) rather than genetics
L- concordance rates may be due to shared learning experience not
genetics= reduced internal validity
what do neural explanations suggests abt offenders?
-may be neural differences in the brains of criminals compared to non-
criminals
-evidence comes mostly from anti social personality disorder sufferers
how is APD characterised?
P3: forensic psychology 2
, -lack of emotional responses like guilt and empathy
how did Raine et al (2000) carry out their research?
-brain scans
-criminal vs non criminal
what did they find?
-11% reduction of vol of grey matter as well as reduced activity in
prefrontal cortex of ppl with APD compared to control
what is a mirror neuron?
-neurons which fire in response to personal action and action of others
-may be involved in interpretation of emotion of others
what did Keysers et al (2011) find?
-only when offenders were asked to empathise with a person feeling
pain in a film was their empathy reaction activated
what did they conclude?
-APD individuals are not totally w/o empathy but may have a neural
switch which they choose when to switch on unlike the normal brain
which has empathy switched on permanently
explain one strength of the neural explanation for criminality
P- support for the link between crime and frontal lobe- brain evidence
E- Kandel and Freed (1989) reviewed evidence of frontal lobe damage
and antisocial behaviour. ppl with such damage tend to show
aggressive behaviour and emotional instability and inability to learn
from mistakes.
E- shows that frontal lobe is associated with planning behaviour
D- empirical and objective- use of brain scans etc
L- supports idea that brain damage may be causal factor in offending
behaviour
explain one limitation of the neural explanation for criminality
P- link between neural differences and APD may be complex
E- Farrington et al (2006) studied group of males who scored high on
APD. they experienced factors during childhood such as being raised
P3: forensic psychology 3
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