Bio-physiological and psycho-social theories of aggression
Aggression has been defined as any ‘’behaviour apparently intended to injure some other
person or object’’ (Bee & Boyd 2004, p. 318). Researchers have been broadly explaining
aggressiveness in two ways; bio-physiological and psycho-social theories. The aim of the
current essay is to discuss and compare some of these theories, and explore their main
contributions to the study of aggressive behaviour.
According to the ethological theory, aggression is rooted in biology and functions as ‘’the
fighting instinct in beast and man…’’ (Lorenz 2002, p. IX). Ethologists claim that any behaviour
that promotes survival and successful reproduction is adaptive. Lorenz (2002) argued that
aggression has played a huge role in the evolutionary development of all species by helping
their members to defend their territories, successfully compete for resources and mates as
well as to establish a social rank order. However, it must be noted that Lorenz based his theory
solely on studies of non-primates. Therefore, applying it to human beings may not be
legitimate. Additionally, this theory fails to explain cultural differences in aggressiveness.
When analysing 30 primitive cultures from the standpoint of peacefulness and
aggressiveness, Fromm (1973) found that only six of these societies were characterized by
much interpersonal violence and aggression. Eight of them were classed as life-affirmative, as
they were characterized by peacefulness, gentleness; with hostility and violence being
extremely rare among these people. The rest were described as non-destructive-aggressive
societies, in which aggressiveness and competition were present, but not central. These cross-
cultural findings suggest that the social context plays a crucial role in the aetiology of
aggression.
Another instinct theory of aggression is the psychoanalytic theory. Freud (1961) proposed
that humans are born with two basic drives; the libido (Eros) and the death instinct
(Thanatos), which together make up the self-centred part of the psyche called the ID. The
death instinct represents an innate destructiveness, which is directed against the self.
However, this aggressive impulse greatly conflicts with Eros, which is why it is often displaced
onto others. Occasionally, aggression is released through socially more acceptable, even
desirable, means such as sports; a process known as sublimation. Both Lorenz and Freud
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, shared the view that aggressive energy accumulates overtime, if unacknowledged, and when
it reaches a certain point, it must be released in some way or another.
There has been some evidence to support Freud’s theory. Megargee (1966) found that
violent crimes are quite often committed by overcontrolled aggressive individuals, who had
been repressing their anger rigorously. She hypothesized that aggressive energy built up in
these people overtime and eventually reached a crucial point, where it exceeded their
defences, and exploded resulting in an excessively aggressive act. However, D’Silva and Dugga
(2010) found little evidence to support Megargee’s hypothesis of an overcontrolled hostility
pattern in offenders with a single violent act. Additionally, Freud’s theory also fails to account
for cultural differences.
Physiological theories of aggression have implicated different genetic deficits as well as
various structural and functional brain abnormalities in the aetiology of aggressive behaviour.
Raine, Lencz, Bihrle, LaCasse and Colletti (2000) found that individuals with antisocial
personality disorder had an 11 per cent reduction in the grey matter of the orbital prefrontal
cortex (OPFC), which is heavily involved in impulse control and emotion regulation, compared
with non-offending and substance-using controls. Similar results were obtained from a study
of male children with conduct disorder (Huebner et al. 2008). Moreover, Brunner et al. (2010)
found that adolescent females with borderline personality disorder, which is also often
characterized by impulsivity and affective aggression, had decreased grey matter volume in
the dorsolateral prefrontal cortices and in the left OPFC compared to healthy controls.
However, these results must be interpreted with some caution. Given that these studies used
very small samples, their findings cannot really be generalized. Mellen (2008) also argued
that not everyone with reduced grey matter behaves aggressively, that suggests that it is only
one of numerous predisposing variables, which is most likely to be correlated with aggression
when other genetic and socio-bibliographical risk factors are also present.
Reduced glucose metabolism in the prefrontal cortices (PFC), which are involved in
personality expression, executive function and social behaviour moderation, has also been
implicated in predisposing to impulsive aggression (Raine 2008). Glucose provides energy for
the brain. Since the glucose use in PFC is reduced, it has been proposed that the brain region
cannot function properly due to insufficient energy. This particular impairment has been
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