>>Actually, decreased testosterone levels tend to cause a male to become more mellow, as I understand it. However, I wonder if steroids could be at work among the belligerent and aggressive types?
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>Nope, when they are in a "normal" range (300 to 1200 for male, 70 to 250 for female) a mellow temperment is apt to be default. When below/above normal, cranky behaviors come on -- irritability, agressive acting out. The somewhat natural deline with aging can result in 'instigating behaviors' in effort to pump T back up. The cranky nursing home guy usually fares better than the passive one. Winners of sporting events have a T rise for while. Winning fans too. The losing team & fans will have a T drop for a while. A bout of illness or injury will cause T to drop until recovery.
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>T is a molecule. While popularly refered to as a "male" hormone, it is required by both males and females. While greater T amounts are usually found in males, much variation can be 'normal' within each sex as one body may respond more or less sensitively than another.
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>I've no handy links at the moment to support the above but if you're interested I'd be happy to dig 'em back up. Just lemme know...

Thank you Steven! I checked a few links and you are correct.