I have a 9 mo. old boxer Roxy who i've tried and tried to train to sit. When i raise a treat over her head and say "sit Rox" she will duck and run. She is a rescue we adopted at 3 mo. old, not sure if there is a history of abuse or not. She isn't really jumpy any other time. Sometimes when I go to get a treat our other two boxers will sit and she'll sit on her own. But when I try to get her to sit she won't. Any advice?
You might like to try setting up a training session that includes Roxy and one of your other dogs. have Roxy pay attention while you use the Sit command with your other dog, giving lots of praise and perhaps even treats (if it's not too distracting for them).
You could also try predicting when Roxy is about to sit, issuing the command, then going overboard with the praise if she follows through. I did this sort of thing with my dog to teach her to urinate on command (quite a useful trick!)
Do you ask your dogs to sit before they are fed? This might be a great opportunity to teach the command, because in my experience, dogs will do almost anything for you if it means they will get some yummy dinner!
It seems to me that Roxy is uncomfortable with people reaching over her head. She may have had a bad experience as a puppy
You could try having her by your side instead of in front of you (a less threatening situation in the doggie world) and instead of reaching to gesture at her head you could try gently pushing on her hind-quarters as you give the command. This may take some time but with lots of praise and few treats she should be sitting on command before you know it.
Multiple short training sessions (~5 minutes each) are always more efficient than a single long session. Involve your other dogs during the training sessions so that Roxy feels like it is part of being in a pack.
