Aggression usually starts with an emotion like annoyance, frustration, or even fear. Children may be unable to control these emotions. When feelings boil up inside, they come out as:
Tense or angry face and body language
Snappish or aggressive tone of voice
Throwing things
Hitting, pushing, kicking, or biting
Where do they get this from?
Everybody gets angry. Children differ in how quickly they feel annoyed or frustrated and how quickly those emotions turn into aggression. Temperament plays a big role in how quickly and how intensely they get angry.
What children do when they get angry is learned either from trial and error or from watching what others do.
They learn that some behaviors make them feel less angry, so they do those behaviors more.
They might also learn that some behaviors get a big reaction from other people, so they do those behaviors more.
Aggression also gives children a lot of control over others- adults, children, and pets- as all are a little afraid of them.
Children who have experienced stress or traumatic events might experience a trauma cue, have a hard time controlling their reactivity and emotions, and jump into an angry outburst.