Do you enjoy arguing?
Turns out there may be a reason why.
New research from Vanderbilt University found that the brain processes aggression as a reward — much like it does with sex, food and drugs.
Researchers believe the finding points to why all creatures have a natural propensity to fight and could explain why people are so fascinated with violent sports like boxing and football.
The study was published online this week by the Journal of Psychopharmacology.
“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 at Vanderbilt, said in a news release. “We have found that the ‘reward pathway’ in the brain becomes engaged in response to an aggressive event and that dopamine is involved.”
For the study, researchers pitted mice against each other, setting up one pair, a male and a female, in a "home" cage and five “intruder” mice in a separate cage.
When the female mouse was temporarily removed from the home cage, an intruder mouse was introduced in her place, triggering an aggressive response by the “home” male mouse. Aggressive behavior included tail rattle, an aggressive sideways stance, boxing and biting.
Researchers also trained the home mouse to poke a target with its nose to get the intruder to return to his cage, at which point it again behaved aggressively toward the intruder mouse. The home mouse consistently poked the trigger, which was presented once a day, indicating the aggressive encounter with the intruder was perceived by the home mouse 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. Dopamine is a neurotransmitter in the brain often associated with pleasure, motivation and 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. “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.”