Humans Crave Violence Just Like Sex

Humans Crave Violence Just Like Sex

Jeanna Bryner / LiveScience Staff Writer
Thu Jan 17, 10:16 AM ET

New research on mice shows the brain processes aggressive behavior
as it does other rewards. Mice sought violence, in fact, picking fights
for no apparent reason other than the rewarding feeling.

The mouse brain is thought to be analogous to the human brain in
this study, which could shed light on our fascination with brutal
sports as well as our own penchant for the classic bar brawl.

In fact, the researcher say, humans seem to crave violence just like they do sex, food or drugs.

Love to fight

Scientists have known that mice and other animals are drawn to fights. Until now, they didn’t know how the brain was involved.

The new study, detailed online this week in the journal
Psychopharmacology, reveals the same clusters of brain cells involved
in other rewards are also behind the craving for violence.

"Aggression occurs among virtually all vertebrates and is necessary
to get and keep important resources such as mates, territory and food,"
said study team member Craig Kennedy, professor of special education
and pediatrics at Vanderbilt University in Tennessee. "We have found
that the reward pathway in the brain becomes engaged in response to an
aggressive event and that dopamine is involved."

Mouse brawl

For the experiments, the researchers placed a pair of mice, one male
and one female, in a cage. Then, the female was removed and a so-called
male intruder mouse entered the cage. That triggered aggressive
behavior in the resident male. The tell-tale signs of aggression
included tail rattle, an aggressive sideways stance, boxing and biting.

After the initial scuffle ended, the resident male mouse was trained
to nose-poke a target to get the intruder to return. Results showed the
home mouse consistently poked the target and fought with the introduced
mouse, indicating, the researchers say, that the aggressive encounter
was seen as a reward.

"We learned from these experiments that an individual will
intentionally seek out an aggressive encounter solely because they
experience a rewarding sensation from it," Kennedy said.

To figure out whether the brain’s reward pathway was involved, the
scientists treated the home mice with a drug to block dopamine in
certain parts of the brain known to be involved in rewards like food
and drugs.

The treated mice were less likely to instigate the intruder’s entry.
“This shows for the first time that aggression, on its own, is
motivating, and that the well-known positive reinforcer dopamine plays
a critical role," Kennedy said.

Human violence

Kennedy explained that the experiments have implications for humans.
The reward pathway in the brains of humans and mice are very similar,
he said.

"Aggression is highly conserved in vertebrates in general and
particularly in mammals," Kennedy told LiveScience. "Almost all mammals
are aggressive in some way or another."

He added, "It serves a really useful evolutionary role probably,
which is you defend territory; you defend your mate; if you’re a
female, you defend your offspring."

Even though it served a purpose for other animals, in modern human
societies, Kennedy said, a propensity toward aggression is not
beneficial and can be a problem.

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Original Story: Humans Crave Violence Just Like Sex

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