I have a 1.5 year old girl who has taken to hitting, which is entirely age-typical. My response is to gently tell her no and put her hand back at her side. Unfortunately she occasionally has to witness one of her parents hitting the other. She learns fast and mimics behavior after witnessing it once or twice so I fear she is learning that hitting is a behavior to imitate. How can I make it clear to her that hitting is wrong out of the presence of her other parent?
Ummm...let's accept that the parental 'hitting' is playful or in no way abusive (think about that one for a minute). The only way to really reinforce the message you want her to get is to stop the hitting.
Unfortunately, children mirror what they see and hear and they pay deeper attention to those things than to specific instructions. Fortunately, this is how having kids can make us better adults.