It seems that elephants aren’t the only large animals out there with an impressive memory: French researchers have confirmed that horses are also able to retain what they learned a long time ago—for better or for worse.

“Once they’ve learned something, they’re not going to forget it easily!” said Lea Lansade, PhD, researcher in the behavior science department of the National Institute for Agricultural Research (INRA) in Tours, France. “And they’re not just going to forget it over time. For riders, that has both pros and cons. If you teach your horse something, he’s going to remember it for years and years, even if you haven’t practiced it in the meantime.

“But the downside is that if he has had a bad experience, he won’t forget that either, and he can pull out his defensive mechanisms against that bad experience many years later,” she said. “He won’t have forgotten it.”

Along with Mathilde Valenchon, MS, PhD candidate in INRA’s behavior science department, Lansade tested 26 horses’ long-term memories. These horses had been used by the same research group in studies related to positive and negative reinforcement two years prior. In one task, the horses had learned to back up when told, “Back!” by the handler and received a food reward. In the second, the horses had to cross an obstacle after hearing a bell ring, to prevent being subjected to a puff of air. In the current study, Lansade and Valenchon tested the horses’ ability to perform the same tasks after two years without practice.

All horses displayed a solid long-term memory in both tasks, regardless of whether the initial reinforcement had been positive or negative and regardless of the horse’s temperament, Lansade said.

“We set out to see how temperament would affect memory, as it does for acquisition,” she said. “But to our great surprise, all the horses—without exception—perfectly retained the exercise they had learned two years earlier, even though none of them had been trained on those tasks during that time. You could almost say it was too easy for them.”

However, when the researchers removed the reinforcement (food reward or air puff) in the current study, the horses tended to stop performing the tasks, she added. And in this scenario, the horses’ temperament appeared to play a role in which ones stopped performing and which ones did not. Specifically, Lansade said, it was the fearful horses in the backing-up test that continued to perform the longest even when the food reward ended. But in the obstacle-crossing test, it was the least sensitive horses that kept performing even when the air puff stopped. Further studies are needed to understand how temperament affects this phenomenon, Lansade said.

Previous research by Evelyn Hanggi, PhD, has already suggested that horses are capable of long-term memory of around 10 years. But this “formidable” study only involved three horses, which could have been “exceptionally talented” with extensive training, Lansade said.

“What we needed was another study that tested a larger group (in our case, 26) of just average riding club horses, who had only been trained in the tasks for a few minutes a day for only 15 days,” she said. “The next study should test a large group of horses for memory as long-term as what we saw in Hanggi’s study, of around 10 years.”

The study, “Characterization of long-term memory, resistance to extinction, and influence of temperament during two instrumental tasks in horses”  (link will appear in an upcoming issue of Animal Cognition.