If your kid says they understand why we don't hit (or kick, scratch, bite), and then does it again anyway, the yes probably isn't the problem you think it is.

 The pencil, the iPad time lost, the toy they didn’t get wasn't the problem. New research says your kid's anger has an address, and it isn't always the one you'd expect.

You've explained the rule clearly, calmly, more than once. It still doesn't transfer to the next situation. New research says the problem was never repetition.