Your Horse’s Brain (A Myth Debunked)

By Terry Golson

The nature of science is that we build on what we know. Sometimes we have to discard ideas when more solid information comes along. Sometimes what has been researched is very, very complex, but the popular press gets hold of it, someone writes a best-selling book inflating it into a whole philosophy, and a little piece of information becomes ingrained into our communal psyche. That’s what happened with the left brain/right brain theory of learning. Over and over it’s been disproven, and yet we still tell ourselves that we’re one sort of person or another and even base teaching methods on it. Yes, we have innate personalities, but it’s not because one side of the brain is dominant. Here’s a good article about this, and here’s some research.

But what does this have to do with horses? Somewhere along the line someone must have read about horse brain anatomy and somehow the facts got skewed so that now there’s a firmly held belief that is detrimental to training. This misinformation taps into that false theory about right brain/left brain independence. This myth claims that one side of the horse’s brain cannot talk to the other. That what a horse sees out of one eye appears so unique to the horse that when the same thing is viewed by the other, it’s as if the horse is seeing it for the first time. This is not true.

The brain has two hemispheres. They communicate rapidly to each other via a ropey-looking structure called the Corpus callosum. It is only when that is severed (surgery or injury) that the two hemispheres act independently (if the individual survives.) Otherwise, the brain’s workings are smoothly integrated. Horses have large, intact, and fully functioning Corpus callosum. This has been proven with high field MRI, and also with a behavioral study. I haven’t been able to find the origin of the myth that the horse either doesn’t have a Corpus callosum, or that it is negligible in size, but that idea is out there. It’s on the American Quarter Horse Association website which states that the horse’s brain is “missing the corpus callosum.” One blog says, “change sides, train a new horse.” This just isn’t so, and if you base training methods on it, you’re doing you and your horse a disservice.

Here Tonka is eyeballing a decorative cairn along the road.


On the way back he eyeballed it again. Not because he thought it was a different pile of rocks, but because he was still interested in what it was. By the time we rode by the cairn on the way home the light had shifted. He knew it was the same pile of rocks, but it deserved a second look. (How a horse tilts its head, how it sees in sunlight and dark does come into play here. Read this about horse vision.) Rocks balancing on each other like that is out of the ordinary. Horses often worry about such things. (Delve into more in the spooking category on this blog.) Because I know that Tonka’s (very intelligent) brain is processing all of this, all he needed was for me to be relaxed, let him think about it, and we were able to ride by without drama.


Your horse’s brain is a miraculous organ. Brain science is still in its infancy. But we do know that the horse has all of its parts intact! And that your horse is fully capable of understanding and thinking through what they see in the world around them. Trust in that intelligence.

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10 thoughts on “Your Horse’s Brain (A Myth Debunked)

  • Gin

    Another interesting blog. Thanks. I have always heard that one-sided brain thing and didn’t have any reason to doubt it. Makes more sense what you wrote about it.

  • Karen Pryor

    Glad to know that the horse has a sensible and smoothly working brain.
    They do like to think, and pause to inspect novelty.
    Only when they are shoved around and forced too much do they shut down. anyway that’s my observation.
    Karen Pryor

  • Brennan

    Great article, Terry. But how do you explain the fact we have to train horses on “both sides” as if they are seeing the action/activity/stimulus for the first time?

    • Terry Golson Post author

      This explains that we don’t have to do that. They are perfectly aware of the world around them, both sides. At the same time. If your horse spooks coming back around, it might be that the shadows, the movement, etc. have changed. It’s not that they don’t know that those objects aren’t there.

  • Elizabeth VanRoss

    Hi Terry. Great article. Anyone studying equine anatomy, or anyone lucky enough to be able to dissect an equine brain, will indeed find a fully functioning corpus callosum. Information received by the brain through all five of the horses senses will be fully processed by its cognitive functions. However, because horses do not think in words, when taught a concept, such as how to place its feet on a curved line to create a circle, the horse will not transfer that information from one side of the brain to the other. The concept must be taught in both directions. Maybe that is where the confusion came from…

    • Terry Golson Post author

      Lucky you to have done a dissection! I don’t quite understand your point. Do animals need words to learn how to travel in different directions? The equivalent of human language? I don’t think so. I wouldn’t use the term “concept” to describe a horse traveling on a circle. “Concept” training for me is more about the intangible, for examples, targeting a specific learned shape; selecting “bigger” from “smaller.” I’d be interested in reading more research about what the corpus callosum is and isn’t capable of. If you have links, do send!

  • Judy

    It’s Humans with their chauvinism that shows me lack of intelligence.. I Find horses are much more intelligent then what they are given credit for . I train my horses on both sides with no issues , just like people they have a more predominant side …. So maybe they are not so much left/right brained but the behaviors associated with such ( put in equine behaviors) I find is very interesting and works .

  • Anna Bakker

    Hello Terry, I am very intrigued by your article. I also always thought the horse was very one-sided. May I ask where you got your information from (scientific articles?) I am writing a small piece about the subject.

    Kind regards 🙂