[ExI] aggression rewarded

[Mike Dougherty]

This reminded me of the EP discussions about war/warlike behaviors...

http://psychcentral.com/news/2008/01/15/brain-views-regression-as-a-reward/1783.html

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Brain Views Aggression As A Reward
By: Rick Nauert, Ph.D.
      Senior News Editor

Reviewed by: John M. Grohol, Psy.D.
      on January 16, 2008

Tuesday, Jan. 15 (Psych Central) -- boxingResearchers have discovered
that the brain processes aggression as a reward similar to sex, food
or drugs. The insight may explain our propensity to fight and our
fascination with violent sports tracing back to Roman gladiators and
extending to current events such as boxing and football.

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

"It is well known that dopamine is produced in response to rewarding
stimuli such as food, sex and drugs of abuse," Maria Couppis, who
conducted the study as her doctoral thesis at Vanderbilt, said.

"What we have now found is that it also serves as positive
reinforcement for aggression."

For the experiments, a pair of mice - one male, one female - was kept
in one cage and five intruder" mice were kept in a separate cage. The
female mouse was temporarily removed, and an intruder mouse was
introduced in its place, triggering an aggressive response by the
"home" male mouse. Aggressive behavior included tail rattle, an
aggressive sideways stance, boxing and biting.

The home mouse was then trained to poke a target with its nose to get
the intruder to return, at which point it again behaved aggressively
toward it. The home mouse consistently poked the trigger, which was
presented once a day, indicating it experienced the aggressive
encounter with the intruder as a reward.

The same home mice were then treated with a drug that suppressed their
dopamine receptors. After this treatment, they decreased the frequency
with which they instigated the intruder's entry.

In a separate experiment, the mice were treated with the dopamine
receptor suppressors again and their movements in an open cage were
observed. They showed no significant changes in overall movement
compared to times when they had not received the drugs. This was done
to demonstrate that their decreased aggression in the previous
experiment was not caused by overall lethargy in response to the drug,
a problem that had confounded previous experiments.

The Vanderbilt experiments are the first to demonstrate a link between
behavior and the activity of dopamine receptors in response to an
aggressive event.

"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. "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."

Vanderbilt University researchers will publish their findings online
in the journal Psychopharmacology.