Sadly, this past month DS has started doing just that. He's obviously testing his boundaries and generally being a cheeky monkey because he laughs after slapping someone. I'd really like to nip this behaviour in the bud before he becomes old enough to learn that this is 'bad' and a good way to get a reaction from someone. He is only 13 months old though so I'm not sure how much he understands what he's doing, or even where he's learnt this from (DH and I have NEVER raised a hand to each other and when I'm in work, DS is cared for by my parents who also don't hit). He is very bright though and I reckon he knows slapping is getting a rise out of someone.
So far when he slaps, we remove his hand and say 'No, we don't slap/hit people. It hurts.' I'm not a fan of time outs/punishment/reward systems at all. Does anyone have any other ways to tackle this?