Biological explanations: Genetic factors

Question 1

Genetics

Answer 1

When looking at how genes affect aggression; this is effectively asking the question of Nature vs Nurture.
The main ways the role of genes in aggression has been examined is through the use of Twin Studies, Adoption Studies and looking at Individual Genes that may play a role.

Question 2

Twin studies

Answer 2

In twin studies; identical twins are compared between non- identical twins for levels of aggression between them. This is be- cause identical twins share the exact genetic makeup as each other while non-identical share only up to 50%.
If identical twins have more similar levels of aggression then it is thought to be due to genetics.

Question 3

Adoption studies

Answer 3

Adoption Studies have looked at examining levels of aggres- sion between adopted children and that of their biological parents. If a positive correlation is found between adopted children and their biological parents then a genetic effect is implied. If a positive correlation is found between the adopted children and their rearing family; a environmental effect is implied suggesting aggression may be due to learning.

Question 4

McGuffin et al (1985)

Answer 4

• In humans aggressive behaviour is more highly correlated with identical twins than in fraternal twins.
• McGuffin found a concordance rate of 87% for ASB for MZ’s compared to 72% for DZ twins.

Question 5

Evaluation of McGuffin et al.

Answer 5

At first glance they support genetics in ASB and aggression.However, these findings indicate that the children are bought up in equal family environments (but it’s diff for MZ’s generally)

Question 6

Mason & Frick (1994)

Answer 6

-Meta-analysis of 12 twin studies (and 3 adoption) involving 3795 twin pairs. They found that 50% of difference between ASB and non-ASB could be due to genetics. (larger estimates of genetic influence)

Question 7

Evaluation of Mason & Frick.

Answer 7

• Meta-analysis means much larger sample than singular study, so potentially cancels out methodological weaknesses in some studies.
• But again twin studies are criticised for assuming equal shared environments.

Question 8

Coccaro et al. (1997)

Answer 8

• Investigates specifically aggressive behaviour rather than ASB or criminal convictions.
• Assessed the degree of genetic and environmental influences on aggression in males.
• Data from 182 MZ’s and 118 DZ’s
• Found that genes accounted for 40% of agg
• Environmental influences on physical agg= 50%
• Environmental influence of verbal agg= 70%

Question 9

Evaluation of Coccaro et al.

Answer 9

• Accounts for both genetic and environmental factors
• Again assumes brought up in equal environments
• Also accounts for different types of aggression.

Question 10

Hutchings & Mednick (1973)

Answer 10

• Reviewed 14000 adoptions in denmark.
• Found a sig positive correlation between the number of convictions for criminal violence among the biological parents and that of their children who had been adopted.

Question 11

Evaluation of Hutchings & Mednick.

Answer 11

• Very large sample so good external validity
• Adoption study so accounts for how genetics are related to environment.
• However the environment could be a factor here with adopted children having a more difficult time adjusting to their environment, learnt behaviour from biological parents previously or even the stigma that is attached with being adopted affecting how they are treated by friends, family and even how they view themselves.

Question 12

Rhee & Waldman (2002)

Answer 12

• Meta-analysis of 51 twin and adoption studies comprising of over 87000 individuals.
• ASB operationalised (behavioural aggression, delinquency, psychiatric diagnoses)
• Genetic influence = 40%
• Environmental influence = 60%
• Little evidence of gender differences.

Question 13

Evaluation of Rhee & Waldman.

Answer 13

• Issues with reporting; these studies included self-reports or reports of pps of similar aggression levels.
• For instance sig differences were found between methods. 39% showed aggression with self reports, and 53% where assessment was done by another person. Shows that method of assessment plays a role in estimates of genetic influence.
• Large sample = good external validity.

Question 14

Overall conclusions of research on twins and adopted children.

Answer 14

• Genetics alone don’t cause aggression, but they may predispose people to aggression.
• Rhee & Waldman suggest that environment is slightly more telling in whether someone will become aggressive.
• Genes perhaps play more of a roles where violence is more serious (Mason & Frick)

Question 15

Why there may an issue with self reports:

Answer 15

• Rhee and Waldman’s study showed that self-reports compared to others assessing the child’s aggression has a significant difference.
• This could be due to the fact when one twin is assessing the other, they use their aggressive twin as a baseline comparison for themselves and so mark themselves low in comparison.

Question 16

Evaluation points: Equal environments.

Answer 16

-One major issue with twin studies is that many researchers assume that MZ and DZ twins raised in the same homes will experience equal living environments. However research has shown that adults (such as teachers, carers, parents) would be more like to treat MZ’s more similarly than DZ’s. This is because they look so much alike, society tends to treat them as the same person.

Question 17

Evaluation: The imperfect nature of twin studies.

Answer 17

-Finding large numbers of MZ twins who are reared apart is extremely rare, therefore researchers must compare MZ’s to DZ’s. However Mz’s are generally treated more similarly than DZ’s. Consequently twin studies are not the perfect genetics versus environment experiment that we would like to imagine.

Question 18

Evaluation: Problems with interpretations of adoption studies.

Answer 18

-One methodological problem is that same countries, such as new zealand +the us, have a higher rate of ASB at the time of adoption than the general pop (sharma et al). Tremblay (2003) maintains that parents who give their child up for adop have higher trends of ASB themselves. Therefore correlations could be due to either genetics, or growing up with ASB parents (environment) prior to adoption and also the feelings of abandonment.

Question 19

Individual genes (MAOA)

Answer 19

Individual genes have also been examined and some candi- date genes have been identified that may play a role. MAOA is a gene that regulates the metabolism of Serotonin which low levels of such have been associated with aggressive impulsive behaviour. A faulty variant of the gene however could result in low levels of serotonin and thus lead to such aggressive behaviour.

Question 20

MAOA Description

Answer 20

• MAOA is an enzyme that breaks down neurotransmitters; noradrenaline, serotonin, and dopamine.
• If the gene responsible for producing MAOA is defected, then these neurotransmitters are not broken down, leaving excess amounts in the bod.
• Each are thought to increase aggression, for instance serotonin and dopamine imbalance are common in aggressive patients.

Question 21

Brunner et al. (1993)

Answer 21

• Conducted a study examining a dutch family who had a history of many of its male members involved with serious violent crimes (rape, Arson). Studying them low levels of MAOA were found and later a defective gene was identified in the male members.
• The defect of MAOA was found in all violent men but none was found in the nonviolent members.
• Brunner et al. believe that excess neurotransmitters may predispose the men to violence under stress.

Question 22

Evaluation of Brunner et al.

Answer 22

Limited influence of gene- It’s unlikely that there is a causal relationship between a single gene and specific behaviour. Genetic deficiencies may exert some influence but not the sole cause.
-Environmental factors-
similar behaviour could also be explained due to similar exposure and learning from role models within the family influencing behaviour through SLT
-Only male members were tested and found to generally have aggressive traits however none of the female members were checked nor were they commonly found to have aggressive tendencies despite having a 50% chance of carrying the gene.

Question 23

Caspi et al. (2002)

Answer 23

-Looked at role of environment in predicting aggressive, antisocial behaviour, specifically at severe childhood maltreatment.
-Those with low levels were associated with higher levels of aggression however only if they were maltreated previously.
Those with high levels of MAOA and were mistreated and those with low levels of MAOA and were not mistreated did not exhibit any anti-social behaviour.
-Tested only 442 individuals

Question 24

Conclusion of Caspi et al.

Answer 24

• Low MAOA on its own did not lead to aggression, maltreatment during childhood was weakly associated with later aggression.
• If a child has a defect of MAOA and the child is subjected to maltreatment, then they will likely show and conduct ASB and have a predisposition towards violence.

Question 25

Deterministic view

Answer 25

This is therefore Deterministic in assuming genes control people and they have little ability for free will or conscious thought which is clearly possible by people. People have the ability of free will and making their own decisions and those found to have “aggressive” genes are not always found to be aggressive.

Question 26

AO2: Role of environment in conjunction with genes

Answer 26

In parallel with these genetic studies of human aggression, Caspi et al (2002) studied the role of childhood maltreatment as a risk factor in later antisocial behaviour and found that boys who experience abuse, e.g. punitive parenting, are at risk of developing into violent offenders. The abuse increases the risk of later criminality by about 50 per cent. However, most maltreated children do not become violent adults. Just as with the MAOA study above, there is no clear cause and effect relationship.

Question 27

Results of Caspi et al.

Answer 27

• They found that the MAOA gene alone was not enough to result in ASB, however when in conjunction with maltreatment as a child it was very significant in showing ASB.
• It also showed that having no MAOA defect, but maltreatment as a child was a high predictor in ASB.
• The data does not reveal that antisocial behaviour is a genetic disease. However, they begin to unravel the complex interplay between genes and environment and perhaps shed light on those who are at risk of developing antisocial behaviour.

Question 28

How does Caspi et al. relate to previous studies on genetics?

Answer 28

The results from Caspi et al. are in conjunction with the results of other studies because the results over all from Caspi showed that environment is more effective in predicting ASB than genes.
-In general it seems that aggression in environment is slightly more important then genes.

Question 29

IDA points

Answer 29

• Practical application: it allows lawyers and criminals ways to identify the route of their aggressive behaviour. It could also allow people to predict aggressive behaviour and so prevent exposure to maltreatment.
• Free will and determinism - these findings suggest that depending on the way your brought up its deterministic to ASB, but we all have free will in what we do, so are they really prone to be aggressive.

Question 30

IDA - issue with studying genetics in ASB

Answer 30

The idea of a gene causing aggression is a determinist one. It might suggest that people with the gene cannot stop themselves from behaving aggressively. However the idea of legal responsibility rests on the assumption of free will, that we can choose whether to commit crimes or not.

Question 31

IDA -> courts changed their mind due to MAOA gene

Answer 31

Courts however seemed to have recognised that people with a defect MAOA gene who have suffered childhood maltreatment are not able fully to exercise free will, for example a Tennessee jury found Bradley Waldroup guilty of voluntary manslaughter instead of first degree murder when genetics was used to support the case.

Question 32

AO2 Evaluation: the positives

Answer 32

Might lead to treatments for personality disorders which are risk factors for aggression (i.e defect and intervene before crime is committed)
-For instance studies of the molecular genetics pathways are leading to the production of pharmaceuticals to fix the pathway problems and hopefully show an observed change in aggressive behaviour. (Nelson & Chiavegatto, 2001)

Question 33

Maori case

Answer 33

-Maori leaders reacted furiously after a scientist said their race carried a ‘warrior gene’ that predisposed them to violence and criminal behaviour. Dr Rod Lea said Maori men were twice as likely as europeans to have MAOA.