Aggression in Men: Hormone Levels Are a Key

Those who had higher levels of testosterone and related hormones had a personality profile that researchers described as ''dominant with some aggressive behavior.''

''The picture we get is of a man who attempts to influence and control other people, who expresses his opinions forcefully and his anger freely, and who dominates social interactions,'' said John B. McKinlay, a psychologist at the New England Research Institute in Watertown, Mass., who was on the research team.