Note: This is unscientific and unproven, only smatterings of my own observations.
"They don't think."
Yeah, they can be. But as pointed out in this post on the Retired Racehorse blog, they can be amazingly patient and kind and careful. Check out Zenyatta and her autistic friend Jack.
Now I don't know a lot about autism (though I did just start reading Horse Boy and have read a book called Speed of Dark) but what I've read often mentions sensory overload--basically too much for the brain to deal with at any given moment and not having the neural processes in place to channel that energy and frustration in what are considered "normal" ways.
Sound a little bit like horses in general and what people consider typical in Thoroughbreds.
Bar seems to have a sensitivity and responsiveness to energy around him that often surprises me. At first, I thought it was just horse energy--other horses setting him off, making him nervous--which made sense from the track background. It's almost like getting outside the pattern and routine of the track presents that horse brain with more options than they can figure out how to deal with, so they do what works for them and over-react.
In working with him, I've seen that it's not just other horses and it absolutely is affected by whatever is going on around him, including and particularly my emotions and energy. The calmer I am, the more confident I am, the better he is.
I've also seen both Bar and Lena bring their own energy down when another horse is acting out, becoming an anchor while another horse spins out of control. Maybe that's what horses sense with autistic people somehow.
No, Thoroughbreds--especially those right off the track--are not for the absolutely green beginner--though sometimes I think I came really close to that description when we got Bar--and they do present challenges and hurdles even for experienced riders. I certainly don't advocate an OTTB as a cure-all, either.
But if Zenyatta is a typical racehorse--a hot, crazy, Thoroughbred--she also has a side Jack can reach. Perhaps it is only that Jack doesn't expect her to be anything but what he perceives--grace, beauty, and gentle power.