@tinyliny and bbsmfg3, That is why our trainer recommended us preforming the join up exercises with him. I have spent time with him in the pasture, as for the first week we had him we just left him be. We are always in the pastrue when we are home, cleaning it up, walking, talking, or repairing stuff. Our other two horses are noisy nellies and have to be right there with us. Their curiosity gets the better of them and they want to know what is going on. Blue, on the other hand, is very standoffish. I believe he associates humans with pain and is just not willing to give his trust again to someone. In the first two weeks we had him, he got to the point where you could touch him at feeding time, but only briefly and slowly. Then he will move off, he is always watching, but will not come close. It is if his flight instinct is full throttle. Once you are able to catch him, he will let you lead him just fine, does not bulk or pressure into your space. He will let you brush and pet him about the back and neck, but if you move anywhere up near the top of his neck or head, he shys away. As soon as you unclip him from a line, he moves off and doesn't want to come near again, even when the other horses come over, unless we are handing out grain or treats. I have trained plenty of dogs using classical conditioning, sit treat sit treat sit treat till you eventually start giving the treat every other time, ultimately getting rid of it. Is it possible to train horses the same way? Half the time I wish I could just get into his's mind and tell him that he is going to be safe and NEVER hurt again.
I work at a rescue where we have a couple horses like this. Two in particular come to mind. One is a gaited Criollo, she was trained as a Spanish Dancing horse (look it up if you don't know - it's just a barbaric act). She is not terribly afraid of people, but she certainly doesn't enjoy people - and trust was non-existant. At the sight of a whip, even just walking by her stall with a stick or pitch fork at first would result in her jogging in place. She has many other issues but it's too long to go all into. Another is an Arabian mare who was well used-up in the show circuit. Not truly "abused" just "used", she has no
interest in humans, they've never meant anything good for her.
At our rescue we use Clicker Training (like your classical conditioning with dogs) - I work with some of the horses and have taught some of the teen volunteers to do it too. The horses I just mentioned now come running to the gait when they see their girl - eager to learn. The criollo will eventually be ridable again with this conditioning (she's still at the beginning stages, but is excelling fast) the Arabian is too lame to be ridden, but she does some sweet ground tricks :)
If you're interested in this style of training - which I understand if you aren't (it can be a tough transition) there are some differences in how you do it versus how you would with a dog or cat. There's a whole thread on it if you're interested: Clicker Training: Challenge Accepted
If that's not for you, I think what everyone else was explaining will help a lot. I think it will just take time and patients and focusing on the positive :)