Biological Explanations of Biological Explanations of AggressionAggression

The role of genetic factorsThe role of genetic factors

Lesson objectivesLesson objectives

Describe the role of genetic Describe the role of genetic factors in aggressive behaviour.factors in aggressive behaviour.

Evaluate the effectiveness of Evaluate the effectiveness of genetic explanations for genetic explanations for

aggressive behaviouraggressive behaviour

The genetic explanation… The genetic explanation… A01 starter…A01 starter…

The genetic explanation for behaviour is The genetic explanation for behaviour is based on the ___________________ based on the ___________________ approach which explains human approach which explains human behaviour and experiences as a result of behaviour and experiences as a result of ________ _________ processes. This ________ _________ processes. This explanation provides that certain explanation provides that certain behaviours are _____________ from behaviours are _____________ from parents and thus adopts the __________ parents and thus adopts the __________ side of the n/n debate. side of the n/n debate.

biological

physical

bodily

inherited

nature

Is Aggression Is Aggression caused by caused by genetics?genetics?

Sandberg 1971 first identified what is Sandberg 1971 first identified what is known as 47 XYY karyotype.known as 47 XYY karyotype.

Most individuals have 46 Most individuals have 46 chromosomes, 23 from each parent, chromosomes, 23 from each parent, it is possible for a male to have an it is possible for a male to have an extra Y sex chromosome making extra Y sex chromosome making them XYYthem XYY

Karyotypes describe the number of chromosomes, and what they look like under a light a microscope

Research evidence for XYYResearch evidence for XYY Court-Brown 1965-67Court-Brown 1965-67, found that of a , found that of a

sample of sample of 314314 patients in patients in a high a high security hospitalsecurity hospital, 15 were found to have , 15 were found to have chromosomal abnormalitieschromosomal abnormalities, including 9 , including 9 who had an extra Y chromosome. who had an extra Y chromosome.

Since the Y chromosome is the male sex Since the Y chromosome is the male sex chromosome and the incidence of XYY chromosome and the incidence of XYY in the general population is 1 in 1000, in the general population is 1 in 1000, this suggests that having an extra Y this suggests that having an extra Y chromosome may have predisposed chromosome may have predisposed these men to increased aggressive these men to increased aggressive behaviour.behaviour.

Court-BrownCourt-Brown concluded that those with concluded that those with XYY would be best kept hospitalised XYY would be best kept hospitalised due to an increase likelihood of due to an increase likelihood of aggressive behaviouraggressive behaviour. .

However! However! A02 criticismA02 criticism Further research into the XYY cerotype has Further research into the XYY cerotype has

revealed that although XYY people are on revealed that although XYY people are on average taller than the general population, average taller than the general population, there is no evidence of increased there is no evidence of increased aggression. aggression. (Milunsky, 2004)(Milunsky, 2004)

Nor… higher than average testosterone Nor… higher than average testosterone levels (Ratcliffe et al., 1994). levels (Ratcliffe et al., 1994).

This suggests that the XYY karyotype is This suggests that the XYY karyotype is not related to aggression at all.not related to aggression at all.

Heritability Studies A02 Heritability Studies A02 SUPPORTSUPPORT

Research on humans has supported the notion Research on humans has supported the notion that genes are an important factor in aggressiveness. that genes are an important factor in aggressiveness.

Rutter et alRutter et al. (1990) carried out a . (1990) carried out a meta-analysimeta-analysiof of twin twin studiesstudies on criminality and found that on criminality and found that Dizygotic twins have Dizygotic twins have concordance rates between 13 & 22%,concordance rates between 13 & 22%,while while Monozygotic Twins have concordance rates between Monozygotic Twins have concordance rates between 26 & 51%.26 & 51%.

Since both types of twins grow up together in the same Since both types of twins grow up together in the same environment, environment, the differences between the two are likely to the differences between the two are likely to be due to geneticsbe due to genetics. .

However, it is important to consider that as monozygotic However, it is important to consider that as monozygotic twins do not show a 100% concordance rate there must be twins do not show a 100% concordance rate there must be an environmental contribution to aggressiveness.an environmental contribution to aggressiveness.

Adoption studiesAdoption studies An adoption study by An adoption study by Mednick, Gabrielli & HutchingsMednick, Gabrielli & Hutchings

(1987) shows an interesting interaction between genes (1987) shows an interesting interaction between genes and the environment. and the environment.

The researchers studied the The researchers studied the criminal recordscriminal records of all of all Danish Danish childrenchildren adopted adopted outside their biological family between outside their biological family between 1924 and 1947. 1924 and 1947.

They reasoned that if the They reasoned that if the criminal records of adopted criminal records of adopted children were more similar to those of their biological children were more similar to those of their biological parents than their adopted parents then this would parents than their adopted parents then this would suggest a genetic component in aggression.suggest a genetic component in aggression.

The resultsThe results did show that did show that having a criminal biological having a criminal biological fatherfather increased the risk of criminality, increased the risk of criminality,

butbut the highest risk was for those with a the highest risk was for those with a criminal criminal biological biological father father andand a criminal adoptive father. a criminal adoptive father.

A02 Evaluation of heritability A02 Evaluation of heritability studiesstudies

The heritability studies, although The heritability studies, although providing support for a genetic providing support for a genetic contribution to aggressiveness are contribution to aggressiveness are limited in that they studied limited in that they studied criminality, rather than criminality, rather than aggressiveness and aggressiveness and not all crime is not all crime is violentviolent. In fact,. In fact,

Mednick and his colleagues reported Mednick and his colleagues reported that the largest effect in their study that the largest effect in their study was for non-violent crime.was for non-violent crime.

Animal Breeding Animal Breeding StudiesStudies

In animal breeding studies, animals In animal breeding studies, animals are selectively bred for certain traits. are selectively bred for certain traits. If it is possible to breed for If it is possible to breed for aggression, this would suggest that aggression, this would suggest that genes contribute to aggressivenessgenes contribute to aggressiveness

Dmitri Belyaev Dmitri Belyaev 19501950

Belyaev's aim was to reduce the Belyaev's aim was to reduce the aggressiveness of the Silver Fox to make them aggressiveness of the Silver Fox to make them easier to breed for their much sought after easier to breed for their much sought after silver fur. silver fur.

He found that after 18 generations the He found that after 18 generations the animals were tame: they approached humans, animals were tame: they approached humans, barked like dogs and even rolled over to have barked like dogs and even rolled over to have their tummies tickledtheir tummies tickled..

Unfortunately for Belyaev, the animals even Unfortunately for Belyaev, the animals even looked like dogs, with floppy ears and a looked like dogs, with floppy ears and a piebald coat – not the silver coat that the fur piebald coat – not the silver coat that the fur industry required. industry required.

The silver fox breeding programme was also The silver fox breeding programme was also able to breed extremely vicious silver foxes, able to breed extremely vicious silver foxes, which supports the hypothesis that genes are which supports the hypothesis that genes are involved in aggression.involved in aggression.

Aggression in mice AO2 Aggression in mice AO2 SUPPORT/CRITICISMSUPPORT/CRITICISM

Other studies have shown that it is possible Other studies have shown that it is possible to breed highly aggressive male and female to breed highly aggressive male and female mice (Cairnes, 1983). mice (Cairnes, 1983).

However, Cairnes found that the However, Cairnes found that the aggressiveness was linked to a particular aggressiveness was linked to a particular developmental stagedevelopmental stage: the animals were : the animals were only aggressive during mid life, but not only aggressive during mid life, but not during early or late life. during early or late life.

Nevertheless, the study does show that Nevertheless, the study does show that genes can affect aggressiveness.genes can affect aggressiveness.

Evaluation of animal research Evaluation of animal research (from both sides) (from both sides)

A problem with research on animals is A problem with research on animals is that it is difficult to generalise the results that it is difficult to generalise the results to humans, nevertheless, mice are often to humans, nevertheless, mice are often used in genetic studies because their used in genetic studies because their genes are homologous (SIMILAR) to those genes are homologous (SIMILAR) to those of humans, this means they produce the of humans, this means they produce the same proteins, which are used in a same proteins, which are used in a similar way. similar way. So, even though there are So, even though there are ___________ issues with animal research, ___________ issues with animal research, it still provides ___________ evidence.it still provides ___________ evidence.

Molecular GeneticsMolecular Genetics

New technologyNew technology has enabled has enabled researchers to examine DNA at the researchers to examine DNA at the molecularmolecular level. level.

Researchers are now able to investigate Researchers are now able to investigate the the proteinsproteins in a particular sequence of in a particular sequence of DNA codes for, which cells in the body DNA codes for, which cells in the body express those proteins and the role of express those proteins and the role of that protein in the body. that protein in the body.

This type of research has produced a This type of research has produced a number of breakthroughs in the effect of number of breakthroughs in the effect of genes on aggressive behaviour.genes on aggressive behaviour.

Chromosones Chromosones

GenesWhich in turn of

made of

consists of lots of

DNA

DNA tells cells what protein to make

MAO-A MAO-A

MAOA gene has been associated with MAOA gene has been associated with increased aggressiveness. increased aggressiveness.

It is sometimes referred to as the ‘Warrior It is sometimes referred to as the ‘Warrior Gene’Gene’

The MAOA gene produces Monoamine Oxidase, The MAOA gene produces Monoamine Oxidase, a chemical that is involved in the breakdown of a chemical that is involved in the breakdown of the neurotransmitters serotonin, dopamine the neurotransmitters serotonin, dopamine and norepinephrine in synapsesand norepinephrine in synapses..

  

What is Serotonin?What is Serotonin? Serotonin is a neurotransmitter.Serotonin is a neurotransmitter.

It can be found in the It can be found in the central nervous systemcentral nervous system (CNS) where it has various functions, (CNS) where it has various functions, including the “regulation of mood” including the “regulation of mood”

Serotonin has effects all over the body:Serotonin has effects all over the body:Low levels of serotonin in the brain can result in Low levels of serotonin in the brain can result in

impulsive behaviour, aggression, overeating, impulsive behaviour, aggression, overeating, depression, alcohol abuse and violent suicidedepression, alcohol abuse and violent suicide

How does this work? How does this work? A01A01

It is thought that having It is thought that having too littletoo little of of the the MAO-A MAO-A gene leads to the brain gene leads to the brain being flooded with being flooded with too much serotonintoo much serotonin, , norepinephrine and dopamine, which norepinephrine and dopamine, which eventually leads to a lowered eventually leads to a lowered sensitivity to these neurotransmitters. sensitivity to these neurotransmitters.

low sensitivity is equivalent to low low sensitivity is equivalent to low activity.activity.

Research evidence A02Research evidence A02 Moffat et al.Moffat et al. (2002) (2002) conducted a conducted a longitudinallongitudinal study of study of

422 males422 males in in New ZealandNew Zealand. He studied their . He studied their history of history of abuseabuse and and criminal convictionscriminal convictions, their penchant for , their penchant for violenceviolence and any symptoms of and any symptoms of antisocial personalityantisocial personality disorder. disorder.

His findings showed that there was a His findings showed that there was a link between MAOA link between MAOA & the risk of being convicted of a violent crime& the risk of being convicted of a violent crime; ; however!..however!.. this was only when participants this was only when participants also suffered also suffered abuse as children. abuse as children.

This is a clear example of a gene-environment This is a clear example of a gene-environment interaction, the gene only exerts its effect in particular interaction, the gene only exerts its effect in particular environmental conditionsenvironmental conditions..

A02 3-POINT PARAGRAPH? IDAA02 3-POINT PARAGRAPH? IDA A03 3-POINT PARAGRAPH? A03 3-POINT PARAGRAPH? MAGECMAGEC

Video Clip: Jim Fallon on the "Warrior Gene"Video Clip: Jim Fallon on the "Warrior Gene"

Summary of main pointsSummary of main points There are several ways in which genetic factors in aggression have There are several ways in which genetic factors in aggression have

been investigated. been investigated. In the 1960s and 70s a popular theory was that males who have In the 1960s and 70s a popular theory was that males who have

inherited an extra Y chromosome are more 'male' and therefore, inherited an extra Y chromosome are more 'male' and therefore, more aggressive; more aggressive;

however, this hypothesis as been shown to be incorrect. however, this hypothesis as been shown to be incorrect. Nevertheless, animal breeding studies consistently show that it is Nevertheless, animal breeding studies consistently show that it is

possible to select for aggressiveness and twin and adoption studies possible to select for aggressiveness and twin and adoption studies in humans suggest that genes influence aggressive behaviour; in humans suggest that genes influence aggressive behaviour;

more recently, psychologists and biologists have developed a better more recently, psychologists and biologists have developed a better understanding of how genes can influence behaviour by using new understanding of how genes can influence behaviour by using new technology to investigate the genetic mechanisms that lead to technology to investigate the genetic mechanisms that lead to increased aggressiveness. increased aggressiveness.

MOA-A production has been associated with aggression. Referred to MOA-A production has been associated with aggression. Referred to as the “warrior gene” by some researchers.as the “warrior gene” by some researchers.

It appears that genes do increase the risk of aggression, but only It appears that genes do increase the risk of aggression, but only when combined with environmental risk factors, such as abuse and a when combined with environmental risk factors, such as abuse and a neglectful family environment.neglectful family environment.

How far does research How far does research support the genetic support the genetic

explanation of aggression?explanation of aggression?In groups of 4: use the 3-point rule to plan In groups of 4: use the 3-point rule to plan

your part of the answer to the above your part of the answer to the above question-specifically identify S.E.Equestion-specifically identify S.E.E

A01: ESSAY PLAN 9 MARKSA01: ESSAY PLAN 9 MARKS

A02: A02 SUPPORT 6 MARKSA02: A02 SUPPORT 6 MARKS

A02: CRITICISM 6 MARKSA02: CRITICISM 6 MARKS

A03: MAGEC 4 MARKSA03: MAGEC 4 MARKS

A02/3 SEE – State the point of evaluation;Explain/evidence for the point of evaluation; Elaborate the point of evaluation (linking to relevant research or deepening the explanation) pgvii f Dog Book

Depth and breadth…

Save your part as

AO1 KNOWLEDGE

AO2 SUPPORT

AO2 CRITICISM

AO3 MAGEC

Exit Pass….Exit Pass….In...pairs write a 3 point A02 paragraph for your given theoryIn...pairs write a 3 point A02 paragraph for your given theory

Example:Example:

‘‘Piaget’s theory is an example of the biological Piaget’s theory is an example of the biological approach….approach….

He claimed that maturatoin was the key to He claimed that maturatoin was the key to cognitive development….cognitive development….

This implies that biological rather than This implies that biological rather than environmental factors are of most importance environmental factors are of most importance in cognitive development’in cognitive development’