Continuous can be defined as ”any behaviour enacted with

Continuous efforts have been made by
researchers to provide an operational and measurable definition for human
aggression. However, there is an overall agreement that aggression can be defined
as ”any behaviour enacted with the intention to harm another person who is
motivated to avoid that harm” (Anderson
and Bushman, 2002, p28). Aggression can manifest itself in many forms such
as instrumental aggression (i.e. terrorism and robbery), hostile aggression
(i.e. impulsive murder and road rage) and relational aggression. There has been
considerable debate surrounding the biological vs. social psychological origins
of aggression, which will be explored.  


Many types of theories have formulated an
answer to the question of whether individuals are biologically inclined to be
aggressive. Theories that explore biological origins have been put forward to
argue that aggression is an innate response in humans, an example being
evolutionary theories. It states that aggressive behaviour was seen as being adaptive
for our ancestors for a number of reasons including deterring mates from
infidelity, defending against attack and co-opting the resources of others (Buss & Shackelford, 1997). One
might argue that these economic and social advantages of aggression were
context-specific, as only when individuals were threatened by these adaptive
problems, did they act aggressively towards others. Evolutionary theories have
also emphasized that there is a gendered difference in the reproduction of
aggression due to intrasexual competition (Trivers,
1972). Males have less parental investment in offspring than females, so this
provides them with opportunities for greater success in reproduction. This
creates greater competition among males to fight for their share of female
mates, to ensure the passing on of their genes to future generations. Contemporary
research has supported the innateness of aggression by exploring the cross
culturalism of aggression in regards to male aggression. Theorists like Craig and Halton (2009) found that
government data in the US showed men are ten times more likely than females to
commit murder and Moffitt et al. (2001)
found in a sample of 1000 individuals living in New Zealand, men were 2.4 times
more likely to be involved in anti-social behaviour.  

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Despite there being clear empirical support
to the claim, there are clear methodological issues. There is a lot of contradiction;
evolutionary theories claim that aggression was used to protect one’s community,
but in a contemporary setting, humans use aggression against their closest
relatives in cases of domestic abuse and child abuse. An example is the brutal
murder of a mother at the hands of her violent ex-boyfriend (The Mirror, 2017). Another example is the
‘House of Horrors’ case, where the parents of 11 children were arrested and
charged with torture, child abuse, imprisonment and sexual assault (The Telegraph, 2018). This may suggest
that evolutionary theories aren’t as applicable to modern society as first
thought, which may be the result of changes in attitudes and social behaviour. Also,
such explanations cannot account for the variability in aggressive acts or
cultures. It fails to provide an explanation for the variation in
aggressiveness in a number of contexts, for instance, where a woman has acted
unfaithful to her husband: in one case her husband beats her, in a second her
husband murders her and in the third case he gets drunk. Furthermore, it
doesn’t explain cultural differences; for example, in the Yanomami culture male
violence is often positively associated with a position of status, whereas in
other cultures violence has negative societal associations. Thus, this
questions the contribution of evolutionary theories regarding how innate aggressive
behaviour is.


Another main theory that supports the biological
perspective of aggression examines the role of hormones and genes. Research has
suggested a positive correlation between the male hormone, testosterone, and
aggressive tendencies. For example, males with high testosterone levels were
more likely to be involved in delinquent and violent behaviour (Archer, 1991). Likewise, serotonin has
been linked to an increase in levels of aggression in humans. More specifically, low levels of the
serotonin metabolite, 5-hydroxy-indole acetic acid (5-HIAA), in cerebrospinal
fluid, has been directly linked with violent behaviour. Birger et al. (2003) supported this as he discovered suicide
attempters who used violent means had reduced levels of 5-HIAA in their spinal


In regards
to the genetic predisposition towards aggression, twin and adoption studies have
explored this. Research looked into the heritability of aggression and found
that 50% of the variance in aggressive behaviour can be explained by genetic
influences in both genders, whilst the other 50% can be explained by
environmental factors (Rhee and Waldman,
2002). Twin studies looked at monozygotic (MZ) and dizygotic (DZ) twins and
found a greater concordance rate of 87% in aggression in MZ twins, who share
100% of their genes, compared with 72% in DZ twins, who share just 50% of their
genes (McGuffin and Gottesman (1985).
An adoption study by Mednick et al.,
(1983) found a strong positive correlation between the number of criminal
convictions of biological fathers and the number of criminal convictions of
their sons, who had been adopted. Therefore, this supports the biological
nature of aggression.


However, evidence for this theory is largely
mixed. There is not yet conclusive evidence to support the theory that hormones
like testosterone and serotonin cause aggressive behaviour. Some research has
contradicted the relationship between testosterone and aggression; Kreuz and Rose (1972) found no
significant differences in
testosterone levels between prisoners who fought frequently and prisoners who
did not, suggesting that testosterone does not play a main role in aggression. The
issue of gender may also confound the results. Research into hormones
focus predominantly on male aggression and therefore suggest that males are
more aggressive than females, but this is not always the case. There are many
instances where a female has committed acts of aggression i.e. murder. Rose West is an infamous serial killer
who was found guilty of the torture, rape and murder of 10 young women, and
sentenced to life in prison in 1995. Therefore, this criticises the biological
study into aggressive behaviour.


In light of these flaws, there is the
argument that aggression has social psychological origins. An explanation of
these origins is the frustration-aggression hypothesis. This suggests that ”frustration
always leads to some form of aggression” (Dollard
et al., 1939) and referred to situations where an individual’s goals or
expectations are thwarted, so they feel frustrated and often engage in
aggressive behaviour. This hypothesis can be applied to a number of contexts
such as sport aggression. Edmans et al.
(2007) found that after players’ positions were altered in a soccer game leading
to poor results, the supporters became frustrated and began throwing objects
onto the field. This shows that because their expectations of the team playing
well were thwarted, they became violent. Therefore, this provides supporting
evidence for the frustration-aggression hypothesis.


However, this theory can be hugely criticised
for being deterministic. It assumes that frustration will inevitably lead to
some form of aggression but this is incorrect. In some cases, there are other
factors that may cause aggression with frustration i.e. social factors like the
location or the presence of weapons. Frustration can lead to a whole host of
emotional responses including sadness, despair and motivation. Frustration does
not only have negative effects, but can be a positive force for change as it
can encourage individuals to challenge the obstacles and work harder towards
their goal. Likewise, aggression doesn’t always occur out of frustration; it
could be the product of revenge, social and economic instability or the lack of
social consequence. Therefore, there is not a clear causal link between
frustration and aggression, and devalues its contribution to the explanation of


Nevertheless, another social psychological
explanation is deindividuation theory, which looks at crowd influence on an
individual’s behaviour. Being part of a crowd leads to a loss of self-identity
(Diener, 1980) and encourages
anti-social behaviour. One might argue that this is due to individuals
believing they are just another face in the crowd, so they are less likely to
be identified and held accountable for their actions. Under these anonymous
conditions, individuals may be more motivated to deviate from the socially
accepted norms of behaviour, and instead turn to violent and aggressive
behaviour. Anonymity has been found to have a direct link to group size; the
larger the size of the group, the more anonymous an individual is, which leads to
a greater engagement in anti-social behaviour (Kugihara, 2001). Research that explores deindividuation theory and
the effect of anonymity focuses predominantly on negative social behaviour such
as aggression. For instance, Silke
(2003) found that perpetrators that committed around half of the violent
assaults in Northern Ireland between the years 1994 to 1996 wore disguises.
Similarly, Douglas and McGarty (2001) discovered
that online individuals are more likely to send harmful content to others, as
their identities are hidden from their victims, and thus would not face any
consequences. This, therefore, provides strong support that when individuals’
identities are hidden, they are more likely to engage in anti-normative
behaviour, disproving the innateness of aggression.


But, deindividuation theory has several
flaws. It assumes that individuals in a deindividuated state will always act in
an aggressive and violent manner, but this is not true. In some contexts, being
part of a crowd can lead to an increase in pro-social behaviours. The
hacktivist group, Anonymous, is an international organisation consisting of an
online and offline community, so identities are protected even in public when
members wear masks to conceal their identity. The group involves itself in political,
social and environmental issues i.e taking down white supremacist sites, protesting
against animal cruelty and hacking pro-ISIS twitter accounts. Supporters of the
group have referred to them as ‘freedom fighters’, whilst others have denounced
them as ‘cyber-terrorists’. Furthermore, there is a lack of supporting evidence
to support deindividuation theory; for example, Postmes and Spears (1998) conducted a meta-analysis of 60 studies
and found that anti-normative behaviour was not more common in large groups or
crowds, contradicting the claim that group membership increases anti-social

Alternatively, there are other models that
looks at the social-environmental causes of aggression in childhood and later
life. This explanation also disproves the biological nature of aggression as it
states that an individual’s social environment is a central factor when
explaining the causes of aggression. The ‘cycle of violence’ theory established
by Wisdom (1989) states that
exposure to a dysfunctional environment in childhood can lead to an increased
risk of exhibiting aggressive behaviour in youth and adolescence. This was later
supported by Loeber et al., (2005)
who said that violent youths are twice as likely to have grown up around high
rates of violence within the family. A dysfunctional environment can be
categorised as childhood maltreatment or conflict.


But, theorists have tried to combine
biological and social explanations of aggression. Recent studies have explored
the gene vs. environment interaction, by looking at the role of the monoamine-oxidase
A (MAOA) gene, and the relationship between exposure to abuse and anti-social
behaviour. Fergusson et al., (2011) discovered
that individuals with low levels of the MAOA gene, who were exposed to abuse in
childhood, were more likely to develop anti-social behaviour in later life.
Like these researchers, Anderson &
Bushman (2002) developed the General Aggression Model, which integrates
social, cognitive, developmental and biological explanations, in the attempt to
explain aggressive behaviour. Thus, this provides us with a holistic approach
that supports the innateness of aggression, but also highlights the social
contexts in which aggression takes place.


To conclude, after considering the evidence, aggression
can be argued to be an innate response in humans through evolutionary theories
and hormonal and genetic research but there is also the argument that it is not,
by looking into social psychological explanations like the frustration-aggression
hypothesis and deindividuation theory. However, the flaws of each of these
theories have called for an integrated approach to truly assess the role of
biology in aggression. Although theorists have attempted this, an example being
the genes vs. environment interaction and the General Aggression Model, there
is always a need for further research to gain a better understanding of human
behaviour, in this case aggression.