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    Men-Commit-Most-Violent-Crimes.-Scientists-Have-St167 Men-Commit-Most-Violent-Crimes.-Scientists-Have-St167 Document Transcript

    • Men commit most violent crimes. Scientists have studied the role of testosterone, the male sexhormone, in the violent and aggressive behaviour.human growth hormone
    • In the laboratory, male mice castration reduces aggression while testosteronereplacement restores aggression in castrated mice The male hormone has aneffect on the organisation of the brain The brain in infancy is sensitive to theeffects of the male hormone, which make it more responsive to the effect oftestosterone in later life However, male individuals differ in theiraggressiveness In one experiment, scientists separated male mice into twogroups: the aggressive and the non-aggressive
    • They were then castrated which reduced their aggression When they gavetestosterone replacement therapy, only those mice that belonged to theaggressive group showed a human growth hormone restoration of aggressivebehaviour In other words, testosterone is necessary for aggressive mice toexhibit aggression, but replacing testosterone is not sufficient to turn apreviously non-aggressive mouse into an aggressive mouse A possibleexplanation for this finding is the idea that early exposure to testosteroneorganizes the brain Testosterone also affects females
    • In female mice, which had their ovaries removed, testosterone - but notestrogen - increases aggressiveness Studies about the relationship betweenhormones and aggression in humans use various methods such as interviews,questionnaires or criminal records to assess aggressive behaviour It doesappear that there is a positive correlation between violence in male and femaleprisoners and circulating levels of androgen Nevertheless, it is unclearwhether androgens facilitate aggression or just encourage social dominance,competitiveness, and impulsiveness It is possible that high levels oftestosterone secreted inside the body encourage behaviour, which aims todominate and enhance ones status over other people
    • Sometimes dominant behavior is aggressive when its clear intent is to inflictharm on another person, but often dominance is aggressive Sometimesdominant behavior takes the form of antisocial behavior, which includesrebellion against authority and law breaking The act of competing fordominant status affects male testosterone levels in two ways The first,testosterone rises in the face of a challenge, as if it were a response to animpending competition The second, testosterone rises in winners and declinesin losers after the competition
    • Thus, there is a two ways relationship between testosterone and dominancebehavior, each one affect the other There are important individual differencesin our response to testosterone In a recent study, research gave testosterone
    • to 56 men aged 20 to 50 years Testosterone treatment significantly increasedaggressive responses on a frustration-inducing computer game involving afictitious subject This effect, however, was not uniform across individuals;most showed little psychological change, whereas a few developed prominenteffect
    • In sports, testosterone increases before competition as a response inanticipation to winning At the same time, winning increases testosterone whilelosing reduces testosterone level These effects also occur in sports fans Thesame effects happen in non-physical games such as chess It is possible thatthese effects are due to changes in status because testosterone increases instudents after graduation and in hostages after their release from captivity
    • Thus, it is possible that these effects will correlate to changes in dominanceStudies have shown that testosterone levels change in response to changes inranking of men There are two possibilities, either testosterone causeschanges in person dominance or dominance affects the level of testosteroneIf testosterone level is a stable personal trait, it is possible to predict a personsaggressive, dominant and antisocial behaviour from measuring this hormone inhis blood Men with higher levels of testosterone are more likely to be arrestedfor offenses (other than traffic violations), to buy and sell stolen property, incurbad debts, or use a weapon in fights
    • On the other hand, testosterone levels vary according to a personsdominance In an interesting study of 2,100 male Air Force veterans,testosterone levels fell and remained low with marriage and rose with divorceIt seems that marriage make men lose their dominance
    • human growth hormone