Defiance
According Webster's online dictionary, defiance means:

1. the act or an instance of defying.
2. disposition to resist : willingness to contend or fight.

I'm going to add a new entry to that...

3. the typical behavior of a child between the ages 1.5 and 3+ years which can drive a parent into complete and utter frustration; a manipulative tactic used by young children in order to gain what they want by throwing tantrums characterized by loud crying, screaming, thrashing on the floor, kicking, and other methods of major drama. Chances of success may vary.