Researchers have defied seven major classes of aggression: predatory, inter-male, fear, irritable, maternal, instrumental (to obtain a goal) and territorial. The amygdala and the hypothalamus, two brain centers, have been centered out as important motivators in aggressive situations. Thankfully, with the potential for such conflict we are given tools in the form of body language that help us gauge aggression in others in order to prevent us from serious injury or death. Since modern humans are primarily vocal, we often ignore some of the cues signifying aggression, but these become very potent as conflict escalates and our verbal language deteriorates to uncontrolled screaming and cussing.