Hitting

A new skill, one I was not expecting to emerge for 6 months yet:  hitting.  Evidence of human depravity I guess, because Banjo sure as heck has never seen Daddy or I do any hitting.  The amusing part is that it is accompanied by a huge smile and a "hih-YAH" sound.  So far Banjo's hitting victims include:

• the dog (on her doggy pillow bed)
• balloons (adrift on the floor)
• my hat (while on my head)
• my nose (while on my face)
• my boob (in the usual location)

How do I gently instruct my 12 month old that "we don't hit" when she is so clearly enjoying the power of her own muscles and the excitement of trying new things?  She does a karate chop and then looks directly at me with that smile, seeking to gauge my reaction.  My brain tells me to give her zero response and to redirect her to another interest.  We'll see how that works.