This is why it is so important to prevent the formation of fear memories associated with riding, trailering, etc. For a horse who has previously been fearful of trailers to overcome his fear, the higher brain centers in the cortex have to send a fear suppression signal to the amygdala. This is called a cortical over-ride, which is a signal that will block the fear me mory but does not delete it. If the animal becomes anxious, the old fear memory may pop back up because the cortex stops sending the fear suppression signal. Fear-based behaviors are complex.
Fear can cause a horse to flee or fight.
For example, many times when a horse kicks or bites, it is due to fear instead of aggression. In a fear-provoking situation where a horse is prevented from flight, he learns to fig ht. Dog trainers have learned that punishing a fear-based behavior makes it worse. When a horse rears, kicks, or misbehaves during training, it may make the trainer feel angry. The trainer may mistakenly think that the horse is angry.