I bought one of those blow-up exercise ball things to play with and use around Diego as a de-spooking object. I also got an "anti-burst" ball, thinking that maybe I could leave it in his corral for him to play with. So this weekend, after a nice lunging session in our remaining slush and mud, I decided to blow up the ball and see how he reacted. He was mildy curious as I was pumping my little heart out, making strange whooshing sounds, but he merely deigned to look across at me with a "And just what are you up to now?" expression.
After it was all blown up (I was disappointed to realized exactly how SMALL the 65 cm ball was), I carried it over to Dig for him to check out. He walked over and sniffed the ball briefly for a millisecond and decided it wasn't worth his attention. So I lifted it up and dropped it over the top rail into the corral, about 4 feet in front of him. He looked at it, bored. So I asked him to put his head down and sniff it, he bumped it with his lip and proceeded to try to go back to napping. So I pushed and kicked the dang thing around (it has sand inside so you have to shove it) and he could hardly be bothered to watch what I was doing. After a bit, I put my hand under his chin (he was loose, not haltered) and had him walk over and "kick" the ball a couple of times by bumping it with a front leg. Overall, he was totally unamused and bored with the whole idea, if "This is stupid and I'm too mature to play" had a face, it was the one he had on.
The only reaction I got from him out of the whole thing was when I finally picked the ball up and threw it over the top corral panel rail and into the barn/shed, over his back and behind his head, where it bumped around and made a few small crashing sounds, at which point he had the decency to hop his back feet over 6 inches to the side so he could see that it was only the ball that made that noise.
So despooking - SUCCESS, toy - FAIL