Horses Remember Training From Years Ago
Research has demonstrated that horses possess exceptional abilities to retain what they've learned. Horses tested in a scientific study remembered how to perform tasks they'd learned as long as a decade earlier, even though the horses had not applied their training during the intervening years.
Researchers tested how well three horses could do the tasks that the animals had been taught years previously, but not revisited since. In one experiment, a horse had learned to use the relative size of items to select the right one. Without any additional training in the intervening seven years, the horse correctly applied the concept about size not only to familiar objects, but also for the first time to items displayed on monitors.
In another test, a horse was trained to select items based on the characteristics they shared within a category. Ten years later, the horse accurately applied that same rule without hesitation to familiar situations, and again with LCD monitors it hadn't encountered before.
In a third test, two horses showed they'd retained what they'd learned about differentiating between stimuli, performing just as well as when they were first trained.
This research confirms what many horse owners have observed: horses do remember events for a long time. Furthermore, the study shows that many years later
Evelyn B. Hanggi and Jerry F. Ingersoll. 2009. Long-term memory for categories and concepts in horses (Equus caballus). Animal Cognition.