Name : Allister Wray
Unit 4 - Criminal & Forensic Psychology
Learning Aim A: Understand different psychological approaches to explaining criminal
behaviour (P1, P2,M1, D1)
Keys: … = references
, Biological approach
Twins studies analyse the concordance rate and the number of MZ and DZ twin pairs who
both portray a particular criminal characteristic. Christiansen (1977) conducted a study into
the concordance rate of 3,586 twin pairs in Denmark. They used criminal records to find that
52% Concordance rate between MZ twins; where one identical twin had a conviction, there
was a 52% chance of the other twin having a conviction. Whereas, amongst DZ twins, there
was only a 22% chance. This suggested that crime might be genetic.
Family studies analyse the extent to which criminal behaviour can be inherited. Frisell et al
(2010) conducted a study into the convictions for over 12 million violent crimes in Sweden
over a period of 3 decades. This was done by using a national register. Frisell et al found
that violent criminals were about 5x more likely to have a first-degree relative who happened
to have been convicted of a violent crime. Frisell et al concluded that violent crime may be
influenced by genes.
Adoption studies are valid as they make it easier to separate genetic and environmental
factors for crime. Hutchings and Mednick (1984) conducted a study that examined data on
over 14,000 adopted sons and their families in Denmark from 1924 to 1947 by using national
police records. They found that sons were more likely to have a criminal record if their birth
parents also had a record. The concordance rate of convicted criminals was about 13%, but
rose to a concordance rate of 20% in a sample of adoptees. By contrast, they found a
smaller proportion (14.7%) had a criminal record if their adoptive parent had one. Hutchings
and Mednick concluded that adoptees with a criminal record were more likely to have
biological parents with a criminal record than those who didn't. This meant crime was
genetically inherited.
Diathesis-stress model provides “a way of combining inherited and learning factors”
(Flanagan. 2019). Hutchings and Mednick (1984) conducted a study that examined data on
over 14,000 adopted sons and their families in Denmark from 1924 to 1947 by using national
police records. They found that if both the adoptive parents and the biological parents had
criminal convictions, the concordance rate in the adoptee rose to 24.5%. Hutchings and
Mednick concluded that genetic inheritance can predispose a person to criminal behaviour.
The MAOA gene’s main function is to trigger a production of monoamine oxidase A that
breaks down neurotransmitters, which leads to an increase of aggression and violent
behaviour. This resulted “in the MAOA gene being nicknamed the warrior gene” (Flanagan.
2019). Brunner et al (1993) conducted a study using a genetic analysis (i.e. urine samples)
of a Dutch family, which found that several male family members had engaged in violent
criminal behaviour (i.e. rape and murder). They found that each of the men were found to
have the MAOA gene. Therefore, they concluded that this suggests that the MAOA gene is
involved in destructive behaviour.
The CDH13 (cadherin) gene’s main function is to trigger a production of protein adhesive
(glue) that sits around the brain’s membranes. “Low levels of CDH13 have been linked to
substance abuse, including alcoholism” (Flanagan. 2019). Tilhonen et al (2014) conducted a
study into 900 criminals from Finland using a national prison register and prisoner
volunteers. They found that around 10% of the violent offenders had a low-activity MAOA
gene and a variant of CDH13. Therefore, they concluded that rather than the genetic pattern
suggesting criminal behaviour, it was the genetic combination that made criminal activity
more likely.
Unit 4 - Criminal & Forensic Psychology
Learning Aim A: Understand different psychological approaches to explaining criminal
behaviour (P1, P2,M1, D1)
Keys: … = references
, Biological approach
Twins studies analyse the concordance rate and the number of MZ and DZ twin pairs who
both portray a particular criminal characteristic. Christiansen (1977) conducted a study into
the concordance rate of 3,586 twin pairs in Denmark. They used criminal records to find that
52% Concordance rate between MZ twins; where one identical twin had a conviction, there
was a 52% chance of the other twin having a conviction. Whereas, amongst DZ twins, there
was only a 22% chance. This suggested that crime might be genetic.
Family studies analyse the extent to which criminal behaviour can be inherited. Frisell et al
(2010) conducted a study into the convictions for over 12 million violent crimes in Sweden
over a period of 3 decades. This was done by using a national register. Frisell et al found
that violent criminals were about 5x more likely to have a first-degree relative who happened
to have been convicted of a violent crime. Frisell et al concluded that violent crime may be
influenced by genes.
Adoption studies are valid as they make it easier to separate genetic and environmental
factors for crime. Hutchings and Mednick (1984) conducted a study that examined data on
over 14,000 adopted sons and their families in Denmark from 1924 to 1947 by using national
police records. They found that sons were more likely to have a criminal record if their birth
parents also had a record. The concordance rate of convicted criminals was about 13%, but
rose to a concordance rate of 20% in a sample of adoptees. By contrast, they found a
smaller proportion (14.7%) had a criminal record if their adoptive parent had one. Hutchings
and Mednick concluded that adoptees with a criminal record were more likely to have
biological parents with a criminal record than those who didn't. This meant crime was
genetically inherited.
Diathesis-stress model provides “a way of combining inherited and learning factors”
(Flanagan. 2019). Hutchings and Mednick (1984) conducted a study that examined data on
over 14,000 adopted sons and their families in Denmark from 1924 to 1947 by using national
police records. They found that if both the adoptive parents and the biological parents had
criminal convictions, the concordance rate in the adoptee rose to 24.5%. Hutchings and
Mednick concluded that genetic inheritance can predispose a person to criminal behaviour.
The MAOA gene’s main function is to trigger a production of monoamine oxidase A that
breaks down neurotransmitters, which leads to an increase of aggression and violent
behaviour. This resulted “in the MAOA gene being nicknamed the warrior gene” (Flanagan.
2019). Brunner et al (1993) conducted a study using a genetic analysis (i.e. urine samples)
of a Dutch family, which found that several male family members had engaged in violent
criminal behaviour (i.e. rape and murder). They found that each of the men were found to
have the MAOA gene. Therefore, they concluded that this suggests that the MAOA gene is
involved in destructive behaviour.
The CDH13 (cadherin) gene’s main function is to trigger a production of protein adhesive
(glue) that sits around the brain’s membranes. “Low levels of CDH13 have been linked to
substance abuse, including alcoholism” (Flanagan. 2019). Tilhonen et al (2014) conducted a
study into 900 criminals from Finland using a national prison register and prisoner
volunteers. They found that around 10% of the violent offenders had a low-activity MAOA
gene and a variant of CDH13. Therefore, they concluded that rather than the genetic pattern
suggesting criminal behaviour, it was the genetic combination that made criminal activity
more likely.
