Human beings destroy each other in numerous wars; murder and violence are incurable even in most happy countries. And in the wild males fiercely fight for the territory and females. Can we compare human aggression to animal aggression (of those who belong to the same species, because hunting for food is not aggressive but feeding behaviour)? The scientists from Russian Academy of Sciences Siberian Branch Institute of Cytology and Genetics (Novosibirsk) consider this comparison to be possible and suggest an experimental model of studying aggression on mice in laboratory conditions.
 

This model falls into such kind of aggression that appears after taking part in multiple conflicts and gaining victory experience. The scientists call it “trained aggression”. Despite the fact that this term is not grammatically correct, it reflects the main point: an individual learns to behave aggressively during his life. This happens to people who have to behave aggressively, e.g. soldiers, secret service officers, professional boxers and wrestlers.
 

To put mice in such condition, the researchers forced males to fight every day. And before fighting potential enemies were kept in the same cage separated with a screen with holes, for they couldn’t touch, but could smell each other. Then the screen was removed and angry males usually destroyed enemy’s nest first and then attacked each other. When mice fight, there always is the winner and the loser, who then behaves as a subordinate. According to the rules of human fight, the winner fights another winner. But scientists made animals follow other rules: next time the winner male fights the loser male of another pair. The experiment continued for 10 or 20 days.
 

The behaviour of both animals changed with time. Timid “victims” tried to run away from the enemy or showed their total irresistance (lying on their back), but it couldn’t help stopping the aggressor, who became angrier and attacked fiercely. The victim’s sorry sight seemed to annoy and to infuriate the aggressor. However, when the experiment was topping off, their behaviour changed again – the victim was less attacked and bit, but the aggressor performed a “forced cleaning” of victim’s coat. This ritual requires less energy, but similarly suppresses the victim. The scientists consider this behaviour to be the result of learning.
 

After the experiment physiological state, standard laboratory tests behaviour and brain biochemical parameters of aggressors and victims were studied. The victims lost weight, testosterone – male sexual hormone – and obtained gastric ulcer and immunodeficiency. This indicates a strong stress. Aggressors were OK, because their behaviour was supported by the victory, they didn’t experience devastating consequences of stress. They became more active, but also nervous and bad-tempered. It’s interesting, that winners, as well as losers, almost lost interest in females.
 

The scientists find much affinity between behaviour of mice and human beings who “learned” to be aggressive. Both again and again try t be aggressive, they like to suppress their enemy and to win. War participants often take part in another war for their own free will, or choose the profession dealing somehow with aggression and violence. For them it means positive emotions because victory is the best prize. But their personality changes, they can be groundlessly cruel and aggressive towards other people, bad-tempered and at the same time nervous. As in mice fights, victim, showing capitulation, doesn’t stop the winner; it causes anger instead of compassion. The roots of this behaviour lie in the same biochemical changes in the brain of a mouse and a human being under continuous aggression.
 

The scientists suggest their model for studying all possible consequences of continuous aggression in the laboratory. They think that it can be used for searching medication, which can normalize behaviour of war participants and for searching ways of decreasing aggression in army troops and sports teams.