I'm not sure horses are capable of because it requires reflective thought.
I'm not sure about this. It's hard to discuss this because the only frame-of-reference we have is our own and so we have to talk about horse-emotions in terms of human-emotions to be able to understands each other.
So when I say "my horse is jealous" I actually mean "if that horse was a human and the human did that way I would identify that behavior and it's related emotion as jealousy" - which can make communication clumsy because there's just too many words there.
I believe horses are capable of choosing to "forgive" - again I don't actually believe that forgiveness is an emotion or behavior that horses have, but I do believe they have a similar emotion that functions in the same way - and I also believe horses can and do make "provisional decisions." For example - as long as that specific human is gentle to me I will be gentle back, but if that same human startles or threatens me I'll get aggressive. Now, I don't think for a moment that horses have this kind of dialogue in their heads, but this is only way I can express the effect or function of what I see my Laska do repeatedly.
He has realized that good things can come from humans. He knows from his horrible past that bad things can come from humans. He knows that co-operating with me is what makes the good things flow, but he also knows that co-operating with humans is what allowed the bad things to happen. He wants the good things from me (the affection as well as the treats from the click) so he literally screws up all his courage (and sometimes he even holds his breath) and tries as hard as he can to co-operate so he can make the click happen and get the treat or calmly approach and get the cuddle. Every once in a while he takes on something that is bigger than his self-control and then he goes back to his old aggressive behavior or he kicks out or in some way explodes.
Let me give you an example. For nearly 9 months I did not attempt to saddle him (or bridle him) while we treated his pain. One day I was saddling Freckles and Laska drove Freckles away and presented his back to me several times in a row. I tentatively placed the saddle on his back. He absolutely smiled. He puffed up with pride and got a twinkle in his eyes and rubbed his head on me. I removed the saddle. He asked again and I laid it on him several times. I reached for the girth and he shied away BUT he stopped after one step, took a deep breath and held it while he stepped back to me and allowed me to buckle the girth. He slowly released the breath and took a step or two, and then he got happy again when he realized he could deal with it.
So it seems to me that he wanted the saddle but hadn't thought about the girth, and had to "talk to himself sternly" to allow the girthing (after he remembered that saddles have girths) and he was "relieved" to discover that he could tolerate it and be "proud" of his achievement.
So, in my opinion, I'm fairly sure that horses can and do practice "reflective thought" but that, while it RESEMBLES human reflective thought it IS NOT THE SAME. I'm also fairly sure that horses can "forgive" but again it IS NOT THE SAME as human forgiveness.
I'm rambling on here, but this something that fascinates me. I have these questions in my head, you see.
Do horses "think"? I say yes, they do.
How do they think? Well, not like humans do
It appears so obvious to me that horses do have emotions and thoughts that resemble ours, and that horses do make choices and decisions, and they strive to understand their environment and clarify what their "responsibilities" are.
Ok, shutting up now ...