2. CONCEPT
• In psychology, the term aggression refers to a range of
behaviours that can result in both physical and
psychological harm to oneself, others, or objects in the
environment. This type of behaviour centres on harming
another person either physically or mentally. It can be a
sign of an underlying mental health disorder, a substance
use disorder, or a medical disorder.
• Social psychologists define aggression as behaviour that
is intended to harm another individual who does not wish
to be harmed (Baron & Richardson, 1994). Because it
involves the perception of intent, what looks like
aggression from one point of view may not look that way
from another, and the same harmful behaviour may or
may not be aggressive depending on its intent.
3. THE BYSTANDER EFFECT
The discussion of bullying highlights the problem of
witnesses not intervening to help a victim. This is a common
occurrence, as the following well-publicized event
demonstrates. In 1964, in Queens, New York, a 19-year-old
woman named Kitty Genovese was attacked by a person
with a knife near the back entrance to her apartment building
and again in the hallway inside her apartment building.
When the attack occurred, she screamed for help numerous
times and eventually died from her stab wounds. This story
became famous because reportedly numerous residents in
the apartment building heard her cries for help and did
nothing—neither helping her nor summoning the police—
though these have facts been disputed.
4. • Based on this case, researchers Latané and Darley (1968)
described a phenomenon called the bystander effect. The
bystander effect is a phenomenon in which a witness or bystander
does not volunteer to help a victim or person in distress. Instead,
they just watch what is happening. Social psychologists hold that
we make these decisions based on the social situation, not our
own personality variables. Social psychologists claim that
diffusion of responsibility is the likely explanation. Diffusion of
responsibility is the tendency for no one in a group to help
because the responsibility to help is spread throughout the group
(Bandura, 1999). Because there were many witnesses to the
attack on Genovese, as evidenced by the number of lit apartment
windows in the building, individuals assumed someone else must
have already called the police. The responsibility to call the
police was diffused across the number of witnesses to the crime.
In general, the greater the number of bystanders, the less likely
any one person will help
5. Factors That Can Influence Aggression
The Role of Biology in Aggression
• Aggression is controlled in large part by the area in the older part of the brain
known as the amygdala. The amygdala is a brain region responsible for regulating
our perceptions of, and reactions to, aggression and fear. The amygdala has
connections with other body systems related to fear, including the sympathetic
nervous system, facial responses, and the release of neurotransmitters related to
stress and aggression.
• In addition to helping us experience fear, the amygdala also helps us learn from
situations that create fear. When we experience events that are dangerous, the
amygdala stimulates the brain to remember the details of the situation so that we
learn to avoid it in the future. The amygdala is activated when we look at facial
expressions of other people experiencing fear or when we are exposed to
members of racial out-groups (Morris, Frith, Perrett, & Rowland, 1996; Phelps et
al., 2000).
• Although the amygdala helps us perceive and respond to danger, and this may
lead us to aggress, other parts of the brain serve to control and inhibit our
aggressive tendencies. One mechanism that helps us control our negative
emotions and aggression is a neural connection between the amygdala and
regions of the prefrontal cortex (Gibson, 2002).
6. • The prefrontal cortex is in effect a control center for aggression: when it is more
highly activated, we are more able to control our aggressive impulses. Research
has found that the cerebral cortex is less active in murderers and death row
inmates, suggesting that violent crime may be caused at least in part by a failure or
reduced ability to regulate emotions (Davidson, Jackson, & Kalin, 2000;
Davidson, Putnam, & Larson, 2000).
Key Brain Structures Involved in Regulating and Inhibiting Aggression
7. Hormones Influence Aggression: Testosterone and Serotonin
• Hormones are also important in creating aggression. Most important in this
regard is the male sex hormone testosterone, which is associated with increased
aggression in both animals and in humans. Research conducted on a variety of
animals has found a strong correlation between levels of testosterone and
aggression. This relationship seems to be weaker among humans than among
animals, yet it is still significant (Dabbs, Hargrove, & Heusel, 1996).
• In one study showing the relationship between testosterone and behavior, James
Dabbs and his colleagues (Dabbs, Hargrove, & Heusel, 1996) measured the
testosterone levels of 240 men who were members of 12 fraternities at two
universities. They also obtained descriptions of the fraternities from university
officials, fraternity officers, yearbook and researcher field notes. The researchers
correlated the testosterone levels and the descriptions of each of the fraternities.
They found that the fraternities that had the highest average testosterone levels
were also more wild and unruly, and they were known across campus for the
crudeness of their behavior. The fraternities with the lowest average testosterone
levels, on the other hand, were more well-behaved, friendly, academically
successful, and socially responsible. Another study found that juvenile
delinquents and prisoners who have high levels of testosterone also acted more
violently (Banks & Dabbs, 1996). Testosterone affects aggression by influencing
the development of various areas of the brain that control aggressive behaviors.
The hormone also affects physical development such as muscle strength, body
mass, and height that influence our ability to successfully aggress.
8. • Although testosterone levels are much higher in men than in
women, the relationship between testosterone and aggression is
not limited to males. Studies have also shown a positive
relationship between testosterone and aggression and related
behaviors (such as competitiveness) in women (Cashdan, 2003).
Although women have lower levels of testosterone overall, they
are more influenced by smaller changes in these levels than are
men.
• Testosterone is not the only biological factor linked to human
aggression. Recent research has found that serotonin is also
important, as serotonin tends to inhibit aggression. Low levels
of serotonin have been found to predict future aggression
(Kruesi, Hibbs, Zahn, & Keysor, 1992; Virkkunen, de Jong,
Bartko, & Linnoila, 1989). Violent criminals have lower levels
of serotonin than do nonviolent criminals, and criminals
convicted of impulsive violent crimes have lower serotonin
levels than criminals convicted of premeditated crimes
(Virkkunen, Nuutila, Goodwin, & Linnoila, 1987).
9. Drinking Alcohol Increases Aggression
• Alcohol increases aggression for a couple of reasons. First, alcohol disrupts
executive functions, which are the cognitive abilities that help us plan, organize,
reason, achieve goals, control emotions, and inhibit behavioural tendencies
(Séguin & Zelazo, 2005). Executive functioning occurs in the prefrontal cortex,
which is the area that allows us to control aggression. Alcohol therefore reduces
the ability of the person who has consumed it to inhibit his or her aggression
(Steele & Southwick, 1985).
• Second, when people are intoxicated, they become more self-focused and less
aware of the social situation, a state that is known as alcohol myopia. As a result,
they are less likely to notice the social constraints that normally prevent them
from engaging aggressively and are less likely to use those social constraints to
guide them. The narrowing of attention that occurs when we are intoxicated also
prevents us from being aware of the negative outcomes of our aggression. When
we are sober, we realize that being aggressive may produce retaliation as well as
cause a host of other problems, but we are less likely to be aware of these
potential consequences when we have been drinking (Bushman & Cooper, 1990).
10. Negative Emotions Cause Aggression
• One kind of negative affect that increases arousal when we are
experiencing it is frustration (Berkowitz, 1989; Dollard, Doob,
Miller, Mowrer, & Sears, 1939). Frustration occurs when we
feel that we are not obtaining the important goals that we have
set for ourselves. We get frustrated when our computer crashes
while we are writing an important paper, when we feel that our
social relationships are not going well, or when our schoolwork
is going poorly. How frustrated we feel is also determined in
large part through social comparison. If we can make
downward comparisons with important others, in which we see
ourselves as doing as well or better than they are, then we are
less likely to feel frustrated. But when we are forced to make
upward comparisons with others, we may feel frustration. When
we receive a poorer grade than our classmates received or when
we are paid less than our coworkers, this can be frustrating to
us.
11. Aggressive Cues
• Weapons : Obviously using a weapon can increase aggression and
violence, but can just seeing a weapon increase aggression? The
answer is yes. Research has shown that the mere presence of a
weapon increases aggression, an effect called the weapons effect.
• Violent Media: Content analyses show that violence is a common
theme in many types of media, including television programs, films,
and video games. The results from hundreds of studies have shown
that violent media increase aggression. The correlation between TV
violence and aggression is only slightly smaller than that correlation
between smoking and lung cancer. Not everyone who consumes
violent media becomes aggressive, and not everyone who is
aggressive consumes violent media. The first violent movie seen can
make a person nauseous. After repeated exposure, however, the
person craves more and more. The effects of viewing violence are
cumulative. Seeing one violent movie probably will not make a
person more aggressive. But repeated exposure to media violence
can have harmful long-term consequences.
12. • Self and Culture
• Norms and Values: Amok is one of the few Indonesian words used
in the English language. The term dates back to 1665, and describes
a violent, uncontrollable madness. A young Malay man who had
suffered some loss of face or other setback would run amok,
recklessly performing violent acts. They believed it was impossible
for young men to restrain their wild, aggressive actions under those
circumstances. However, when the British colonial administration
disapproved of the practice and began to hold the young men
responsible for their actions, including punishing them for the harm
they did, most Malays stopped running amok.
• The history of running amok thus reveals three important points
about aggression. First, it shows the influence of culture: The
violence was accepted in one culture and prohibited in others, and
when the local culture changed, the practice died out.
13. Second, it shows that cultures can promote violence without placing a
positive value on it. There is no sign that the Malays approved of
running amok or thought it was a good, socially desirable form of
action, but positive value wasn’t necessary. All that was needed was for
the culture to believe that it was normal for people to lose control under
some circumstances and act violently as a result. Third, it shows that
when people believe their aggression is beyond control, they are often
mistaken—the supposedly uncontrollable pattern of running amok died
out when the British cracked down on it.
• Self-Control: In 1990, two criminologists published a book called
A General Theory of Crime. Such a flamboyant title was bound to
stir controversy. After all, there are many crimes and many causes,
and so even the idea of putting forward a single theory as the main
explanation was pretty bold. Criminals seem to be impulsive
individuals who simply don’t show much respect for norms, rules,
and standards of behavior.
14. If self-control is a general capacity for bringing one’s behavior into line with
rules and standards, criminals lack it. Another sign is that the lives of
criminals show low self-control even in behaviors that are not against the law
(e.g., smoking cigarettes).
• Culture of Honor
The southern United States has long been associated with greater levels of
violent attitudes and behaviors than the northern United States. In comparison
to northern states, southern states have more homicides per capita, have fewer
restrictions on gun ownership, allow people to shoot assailants and burglars
without retreating first, are more accepting of corporal punishment of
children at home and in schools, and are more supportive of any wars
involving U.S. troops. Social psychologist Richard Nisbett hypothesized that
these regional differences are caused by a southern culture of honor, which
calls for violent response to threats to one’s honor. A similar culture of
violence exists in the western United States, or the so-called Wild West,
where a cowboy could also lose his wealth quickly by not protecting his herd.
(Cowboys herded cows, hence the name.) This violent culture isn’t confined
to the southern and western United States; cultural anthropologists have
observed that herding cultures throughout the world tend to be more violent
than agricultural cultures.
15. • Humiliation: Humiliation appears to be the primary cause of violence and
aggression in cultures of honor. Humiliation is a state of disgrace or loss of self-
respect (or of respect from others). It is closely related to the concept of shame.
Research shows that feelings of shame frequently lead to violent and aggressive
behavior. In cultures of honor there is nothing worse than being humiliated, and
the appropriate response to humiliation is swift and intense retaliation.
• Age and Aggression: Research has shown that the most aggressive human
beings are toddlers, children 1 to 3 years old. Researchers observing toddlers in
daycare settings have found that about 25% of the interactions involve some
kind of physical aggression (e.g., one child pushes another child out of the way
and takes that child’s toy). High aggression rates in toddlers are most likely due
to the fact that they still lack the means to communicate in more constructive
ways. No adult group, not even violent youth gangs or hardened criminals,
resorts to physical aggression 25% of the time.
Young children do not commit many violent crimes, especially as compared to
young men. This is most likely due to the fact that young children can’t do much
physical damage, because they are smaller and weaker. Longitudinal studies show
that serious aggressive and violent behavior peaks just past the age of puberty. After
the age of 19, aggressive behaviors begin to decline. However, a relatively small
subgroup of people continue their aggressive behavior after adolescence. These
“career criminals” typically started violent offending in early life. The earlier the
onset of aggressive or violent behavior is, the greater is the likelihood that it will
continue later in life.
16. • Gender and Aggression: Research shows that males are more
physically aggressive than females, but this difference shrinks when
people are provoked. Males are also more verbally aggressive than
females, although the difference is much smaller. Females are often
taught to be less direct in expressing aggression, so they often resort
to more indirect forms of aggression. When it comes to relational
aggression, for example, females are more aggressive than males.
Relational aggression is defined as intentionally harming someone’s
relationships with others. Some examples of relational aggression
include saying bad things about people behind their backs,
withdrawing affection to get what you want, and excluding others
from your circle of friends. Thus, rather than simply stating that
males are more aggressive than females, it is more accurate to state
that both sexes can behave aggressively, but they tend to engage in
different types of aggression.
17. • Aggression and Biased Social Information Processing: People do not passively
respond to the things happening around them, but they actively try to perceive,
understand, and attach meaning to these events. For example, when someone
bumps a shopping cart into your knee in the local supermarket, you will likely do
more than just feel the pain and take another carton of milk from the shelf.
Instead, you will try to make sense of what happened to you (often this occurs
automatically and so fast that you’re not even aware of it): Why did this person
bump me? Was it an accident or was it intentional?
According to the social information processing model, the way people process
information in a situation can have a strong influence on how they behave. In
aggressive people, the processing of social information takes a different course than
in nonaggressive people. For example, aggressive people have a hostile perception
bias. They perceive social interactions as more aggressive than nonaggressive people
do. Aggressive people pay too much attention to potentially hostile information and
tend to overlook other types of information. They see the world as a hostile place.
Aggressive people have a hostile expectation bias. They expect others to react to
potential conflicts with aggression. Furthermore, aggressive people have a hostile
attribution bias. They assume that others have hostile intentions. When people
perceive ambiguous behaviours as stemming from hostile intentions, they are much
more likely to behave aggressively than when they perceive the same behaviors as
stemming from other intentions. Finally, aggressive people are more likely than others
to believe that “aggression pays.” In estimating the consequences of their behavior,
they are overly focused on how to get what they want, and they do not focus much on
maintaining good relationships with others. This is why aggressive people often
choose aggressive solutions for interpersonal problems and ignore other solutions.
