cocker spaniel won't come when called(teaching a dog to come)

[Micky Moo]

My pooch likes to be different. We rescued him from the pound, and he had no idea what obedience was, let alone training. It took me 2 and a half months to teach him to Shake Paws. Now he's got the gist of learning, he is very quick to pick up things.

I digress: My pooch will come when called if we are out (I still keep him on a long leash as I have a spinal disorder and cannot run after him if he did decide to run off), but if we are at home and he can see me and I call him to me, he just sits there and watches me. He might deign me with his presence after a minute or so, but never straight away. I use the clicker method to train him and whilst training he obeys every command, I have slowly tried to randomise the treats, but he seems to know if he will get a treat or not. My trainer said it was all to do with body language, so I have tried hard to show the same look and body language with or without a treat, but he just seems to know.
How can I make him come every time, with or without treats. (I NEVER click without a reward!)

[spin]

I realized quickly with my pup, that good things must happen when he comes on command.

of course treats are great, but you must be careful what happens when the dog does come.

Never use the come command prior to punishment, or when you are ending the fun.

If coming means it is time to go inside, then the dog will be less likely to obey. If possible, go get the dog in this situation. Practice the come command when you can simply treat or praise and then let the dog go back to what it was doing.