Science, as much as I love it can be and often is wrong. When you start applying it to living beings then you have no absolutes.
I've seen a welsh B eye up an electric fence, try to push it down and get zapped, so he turned sideways and pushed it with his rug. Has a horse got the brain power to do that? According to science no he hasnt, having seen it I have to say they have.
I've also seen a pony let itself out of the stable, go round and open all the other stables, he didnt find any food (i presume that was what he was going for) and then headed for the feed room (it was at this point that I intervened). Again science says he should not have been able to reason enough to open the bolts on those doors and he certainly shouldnt have been able to figure out how to open the kickbolt at the bottom of the door.
I've watched a horse wiggle its way out of a rug without damaging itself or the rug (I sat and watched because I was sick to death of finding expensive rugs inside out, soaking wet in the middle of the field). Deffinate premeditation there. The horse must have wanted the rug off and figured out a way to get it off. Unfortunatly for me he did it on a regular basis.
I've had enough experiance with horses to know that there are no absolutes with them and this seems to be something you are lacking.