It's because they have a poorly developed prefrontal cortex of the brain :) That is why Blacks tend to be so loud, compulsive, spontaneous, rude, rowdy, aggressive, etc... Due to the fact that they have a poorly developed prefrontal cortex they have a more difficult time than Whites do at controlling their emotions and impulses.      This is a description of the prefrontal cortex of the brain and it's functions......     This brain region has been implicated in planning complex cognitive behaviors, personality expression, decision making and moderating correct social behavior. The basic activity of this brain region is considered to be orchestration of thoughts and actions in accordance with internal goals.