Marvin Minsky believes that our brain works in several levels:
Reflective Brain
Deliberative Brain
Reactive Brain
External World

As the external world changes, the reactive brain might create an instant instinctive reaction. Negative reactions out of fear, for example, almost always "light up" the amygdala portion of the brain. But the amydgala also is known to shrink in human males after they are castrated. So this part of the brain is both involved in reactive and agressive forms of action.

Living Systems

Type-4 life is a name for organic life. It tends to reproduce itself, (human males and others excepted) and depend on ego or self-interest to be in existence. A water glass is a form of type-5 life and you will notice that it is neither squishy nor egotistical. It depends on others for its reproduction. If you have an attractive glass, friends will ask about it and ask for it at the shops in town. This demand, external to the glass itself, is what causes the glass to be reproduced, not any self-aggrandizement.