Gifted Issues Discussion homepage Forums General Discussion behavior systems???

I agree with Taminy's advice.
You may want to try a punisher - loss of privelege - for aggression if it continues. I would try the positive approach first though. I would also suggest you ignore the agression and walk away (assuming your child doesn't self-injure of isn't at risk of hurting anyone else). If your son is doing this to gain access to tangibles then make sure you don't give into his demands no matter what, especially when he's hitting you.
By ignoring, I don't mean ignore the child, I mean specifically ignore the behavior. Avoid statements during the heat of the moment like "no hitting". I know this is a hard one for parents to grasp but it all comes down to attn. Now this does not mean you should not discuss more appropriate ways of getting wants met when your child is calm - just never during the behavior itself.
It's really hard to assess like this so you may want to seek help from a professional should the aggressive behavior continue.
Also, there's plenty of peer-reviewed research on the successful use of token economies, etc. published in reputable journals. I don't have the links but folks are welcome to google - The Journal of Applied Behavior Analysis, or Behavioral Interventions - just to name a few.