In general the Cerebral Hemispheres of the horse are not connected very well.
This causes a bad communication between the two different sides of the brain. Therefore not all information that enter one side of the brain automatically also reach the other side.
This explains the balking reaction of horses. When they got used to a new object only from one side they will possibly balk when they see the new object the first time from the other side. The information (“Don’t worry- this object is new but no danger“) simply did not get communicated to the other side of the brain.
However, there are some methods that help to train the communication inside the brain. Especially the training methods invented by Michael Geitner from Rechtmehringen in Germany help to activate the awareness of the horse. Here you can find all detailed information about this successful training!