Genetic Factors

Question 1

Outline Lagerspetz’s study from 1979.

(Supports the role of genetics within aggression)

Answer 1

Supports the role of genetics within aggression.

This is because they raised mice in isolation, and separated the mice into two groups depending on the level of aggression displayed when they were mixed with other mice: aggressive mice (TA) and non-aggressive mice (TNA); they were then interbred.

By the 19th generation, aggressive biting behaviour in TA mice was 52%, but in TNA it was only 5%.

The TA mice also had heavier testes than their TNA counterparts, and increased serotonin levels.

This suggests that aggressive traits can be passed through genetics, showing the influence of a person’s disposition for aggression.

However, both mice groups were able to be tamed - suggesting that their environment had also influenced them.

Question 2

What are the 3 main ways that you can study the link between aggression and genetic make-up?

Answer 2

Twin studies.

Adoption studies.

Family studies.

Question 3

Why do psychologists prefer to use non-human animals instead of humans, in research for aggression?

Answer 3

The populations (twin studies), (adoption studies), (family studies) are naturally occurring.

Psychologists sometimes prefer to manipulate the situation by using animals that have been specifically bred to investigate aggression.

Question 4

Why is it sometimes better to use animals over naturally occurring human studies? Give an example of this in a study.

Answer 4

Can manipulate variables.

Control the environment.

Establish cause and effect with more certainty.

E.g. Lagerspetz’s mice, you can easily look at the genetic and heredity effect quickly, compared to that of humans. Such animals such as rabbits can have around 3 litters each year.

Question 5

Outline the study completed by Coccaro et al in 1997.

(Supports the role of genetics within aggression)
(Twin studies).

Answer 5

Supports the role of genetics within aggression.

This is because when they studied adult male MZ and DZ twins, concordance rates of 50% between MZ twins for direct physical assault and 28% for verbal aggression. (This was significantly higher than 19% and 7% for DZ twins).

This suggests there are genetic factors for some human behaviours, and concordance rates being higher in MZ than DZ lends support for genetics in this behaviour.

However, it could also challenge genetics, as concordance rates are not 100%, so environmental factors such as childhood upbringing may have also contributed.

Question 6

Outline the study completed by Waldman et al in 2002.

(Supports the role of genetics within aggression)
(Adoption studies).

Answer 6

Supports the role of genetics within aggression.

This is because their meta-analysis of adoption studies on direct aggression and anti-social behaviour found that genetic influences accounted for 41% of the variance in aggression, more or less in line with the findings from Coccaro’s twin studies.

This is really compelling evidence for genetic influences in aggression, as variance is usually a lot lower, this is very high.

This suggests that genetics had a greater influence on aggression in studies using self-reports rather than parent or teacher reports.

This may have been due to social desirability bias, with parents wanting their children to look well behaved, and teachers want the school to look good; moreover, parents are not always told everything by the kids, so external reports potentially not as accurate as self-report.

Question 7

Outline the study from Brunner et al, 1993.

(Supports the role of genetics within aggression)
(Family studies)

Answer 7

Supports the role of genetics within aggression.

This is because when they studied 28 male members of a large Dutch family who were reportedly involved in impulsively aggressive violent criminal behaviour e.g. rape and murder, they found that these men had abnormally low levels of MAOA in their brains and the low-activity version of the MAOA gene.

This suggests that the aggression may have been a result of abnormalities in levels of NTs.

However, they are a family, so they are all likely to have been influenced by the same environmental effects, (e.g. same role models and traumatic events).

The research findings are also only correlational, as it is not certain that the NTs caused the aggressive acts.

Question 8

What does MAOA stand for?

Answer 8

Monoamine oxidase A.

Question 9

What is the MAOA gene?

Answer 9

An enzyme.

Its role is to break down NTs in the brain after a nerve impulse has been transmitted from one neuron to another.

E.g. It breaks down serotonin into its constituent parts.

Question 10

What is an enzyme?

Answer 10

Biological catalysts that break things down.

Question 11

Give 3 examples of monoamines.

Answer 11

Serotonin.

Noradrenaline. (When in nervous system, acts as a NT).

Dopamine.

Question 12

What determines enzyme production?

Answer 12

Enzyme production is determined by MAOA gene.

Question 13

How does a dysfunction in the MAOA gene result in aggressive behaviour?

Answer 13

A dysfunction in the operation of this gene may lead to abnormal activity of the MAOA enzyme.

This, will then affect e.g. levels of serotonin in the brain.

This may be an abnormal increase or decrease.

Question 14

Does everyone with a MAOA gene dysfunction have increased aggressive behaviour?

Answer 14

No, as it is allele dependent.

Question 15

What is the name of the allele of the MAOA gene that leads to low MAOA activity in brain areas?

Answer 15

Warrior gene.

Question 16

What has the warrior gene (allele of MAOA gene) been associated with?

Answer 16

Associated with various forms of aggressive behaviour.

Question 17

Outline the study completed by Stuart et al in 2014.

(Supports the association between the MAOA gene and aggression)

Answer 17

Supports the association between the MAOA gene and aggression.

This is because when they studied 97 men who, because they had been involved in inflicting intimate partner violence (IPV), were part of a batterer treatment programme, they found that men with the low activity MAOA gene were the most violent perpetrators of IPV; engaging with the highest levels of physical and psychological aggression, and inflicting the worst injuries on their partners.

This suggests that the low MAOA gene levels are potentially a cause for aggressive acts.

However, it would be reductionist to only consider one gene, and exclude the role of the environment.

It is also androcentric, which restricting findings to men - leaving female vulnerability unknown.

Question 18

Do genes function by themselves?

Answer 18

Genes are crucial influences on aggressive behaviour but they do not function in isolation.

Question 19

What else must be present for low MAOA gene activity to relate to adult aggression?

Answer 19

Low MAOA gene activity is only related to adult aggression when combined with early traumatic life events.

Question 20

Outline Frazzetto et al’ study from 2007.

(Supports diathesis stress within the MAOA gene explanation for aggression)

Answer 20

Supports diathesis stress within the MAOA gene explanation for aggression.

This is because they found an association between higher levels of antisocial aggression and low-activity MAOA gene allele in adult males, but only in those who had experienced significant trauma (e.g. abuse) during the first 15 years of life.

Those who had not experienced such trauma in their childhood did not have particularly high levels of aggression as adults, even when they possessed the MAOA low-activity allele.

This suggests that diathesis and stress contribute to the formation of aggression.

Question 21

Outline Moffitt et al’s study from 1992.

(Supports diathesis stress within the MAOA gene explanation for aggression)

Answer 21

Supports diathesis stress within the MAOA gene explanation for aggression.

This is because when they studied 442 New Zealand males studied from birth to age 26, it was found that those who had suffered abuse and had the low activity version of the gene were 9x more likely to indulge in anti-social behaviour, including aggression.

This suggests that diathesis and stress contribute to the formation of aggression.

Question 22

Can we separate nature and nurture in the explanation of aggression for genetics?

Answer 22

Your environment interacts with your genes.

You might have the genes for a certain behaviour, but your environment controls its expression.

The interlinking is so strong, there is no way to separate the two.

Question 23

Outline ‘reductionist’ as an evaluative point of using a single gene as an explanation for aggression.

Answer 23

Reductionist, as it only focuses on a specific explanation.

Aggression is such a complex behaviour: this can be seen through the types of aggression.

The situation in which someone might act is so vast, so you cannot reduce all examples to a single gene.

Question 24

Outline ‘biologically deterministic’ as an evaluative point of using a single gene as an explanation for aggression.

Answer 24

Biologically deterministic, as it renders behaviour genetically lawful and predictable.

Frazzetto’s research was biologically and environmentally determinism.

Instead, a holistic approach should be taken, considering the individual as a whole, e.g. the person and their environment.

Question 25

Outline Stuart et al’s study.

(Supports a more holistic viewpoint on genetic roles in aggression)

Answer 25

Supports a more holistic viewpoint on genetic roles in aggression.

This is because they found intimate partner violence in men was associated with the 5-HTT gene (influences serotonin activity in the brain) as well as low activity MAOA genes; it was found that the combination of the two genes was most closely linked with IPV.

This suggests that more than one gene is involved in aggression

However, only studying two genes is still really reductionist.

Question 26

Outline Vassos et al’s study from 2014.

(Challenges the singularity of genes in aggression)

Answer 26

Challenges the singularity of genes in aggression.

This is because their meta-analysis found no association between any single gene and aggression.

Their explanation for this surprising result is that even several genes are unlikely to fully explain a behaviour as multifaceted as aggression.

The researchers calculated that hundreds or thousands of genes interact in a complex way to determine aggressive behaviour, casting doubt over any search for single candidate genes.

This suggests the diathesis stress explanation is more valid, as all genes of all different behaviours can manifest aggression.

Question 27

Outline Mertins et al’s study from 2011.

(Supports the idea that low activity alleles of the MAOA gene is involved in aggression, and high activity alleles of the MAOA gene is involved in being more placid)

Answer 27

Supports the idea that low activity alleles of the MAOA gene is involved in aggression, and high activity alleles of the MAOA gene is involved in being more placid.

This is because when they studied PPs with low-activity and high-activity alleles of the MAOA in a money-distributing exercise, they found that males with high-activity allele were more co-operative and made fewer aggressive moves than the low-activity PPs.

However, this is quite a weak supporting evidence, as it has low mundane realism; the task is not natural and performed under lab conditions.