Simply "forget."

Kids love to "forget."  They can be told not to do something one thousand times, yet kids insist on continuing to do what they were told not to.  Even though a child can be looking right at you while you are speaking to them about what not to do, they will end up repeating their wrong behavior.  And when your back is not even turned and you can plainly see them, they go back to doing what you just reminded them not to.  Ah yes.  Children are not dumb.  They are highly intelligent.  Yet they push those buttons of any one watching them, more so the parents, to see what they can get away with and if the guardian will react.
For instance, my oldest daughter, Rachael, has been reminded time and time again to not sit on the upper part of the couch.  Yet she still insists that anywhere on the couch except for the couch cushions is her seat.  Her lazy boy.  Even with her dad and I constantly lecturing her on what could happen if she fell, how its damaging to our sofas, and how its setting a bad example for her younger siblings, she continues to sit everywhere on the couch but.  And discipline seems to not work wonders of any kind.  Even though she kicks and screams on her way to the corner, and it looks as though it is going to be a terrible, horrible, tormenting punishment for her, she still quite simply "forgets" why she was sent there and goes right back to sitting on the upper part of the couch.  When asked why she hasnt listened, her answer is always the same, "I dont know." 
You would think that this action would stop after being lectured more times than one has fingers and toes.  Of course not. 
Another example.  Every morning when I wake my oldest daughter up for school, routine should be to get up, get dressed, and come out for breakfast.  Does she do that?  Nope.  Almost every morning, she is caught in her room playing with her toys while still sitting in her pajamas.  I have to tell her to get dressed.  No, no, no...REMIND her to get dressed.  Then I ask her why she hasn't.  Her answer hasnt changed...."I don't know."  Ugh!  She knows.  There is just that switch in a childs head that I guess has not turned on yet.  Or she is that wise that she knows what she is supposed to do yet she makes it that much more stressful on me in the mornings or when she is doing something she knows better on.  It is almost purposeful. 
Children do know.  They do remember what they are to do and what they are not to do.  Yet it is a game.  It is a test.  Seeing what they can get away with.  It is almost like kids do it on purpose so that eventually we just give up as parents.  Like I said, children are highly intelligent.  Do not turn your back on the attempted "masters" of plan.