Our three yr old daughter hits our eight month old every now and again - once a week it seems over the past 6 weeks or so - usually when she is tired and he steals her barbie doll etc!
we abhor hitting. we put her in time out for 3-5 mins and explain firmly this is very bad and daddy doesnt hit and mummy doesnt hit and neither must she.
...but this has happened 4 or 5 times now.
I'd be interested to know if you think its possible to actually stop the hitting completely ie should we be making more of a deal of this with her (20 min timeouts/very strong disapproval)