Behavior

All I need is a good night’s sleep

Horses need a good night’s sleep to support learning and coping, just as humans do. A recent study at the University of Helsinki found that short periods of rapid eye movement (REM) sleep impair a horse’s perseverance and performance in demanding learning tasks.

Mira Hämäläinen, DVM, who is on the veterinary faculty at the University, and her colleagues investigated equine learning using a reverse learning test designed by her research group. In the test, the horse is taught to touch an object for a reward. When the horse learns the task, the setting is changed, the correct object is changed, and the horse must adapt its actions. The test can be done in the field, she said.

Most of the riding school horses involved in the study learned the task and completed the test successfully. Learning was measured by counting the number of correct responses per minute. This proved to be a sensitive and practical way of monitoring the horses’ progress.

“Our reverse learning test can be completed in a single day in the horse’s own enclosure. Traditionally, learning has been investigated through tests that take several days. Requiring only 2 people and simple equipment, the new test is easy to apply in practice,” Dr. Hämäläinen said.

Coping hinges on REM sleep quantity
Sleep is a central pillar of learning and memory in all animal species studied. Insufficient sleep impairs the formation of memory traces, as well as attention, motivation and flexibility when awake.

Dr. Hämäläinen’s study monitored nighttime REM sleep in 16 riding school horses (14 geldings and 2 mares) for 6 weeks, measuring their sleep cycle 5 times over 48 hours. Twelve of the horses were Warmbloods, and 3 were Finnish horses.

The results were clear: Horses with REM sleep lasting more than 30 minutes per night performed better in the reverse learning test than those with a shorter duration of REM sleep. “Shorter REM sleep did not increase the number of mistakes, but it had a particular effect on how long the horses worked on the task,” Dr. Hämäläinen said.

In other words, all the horses were able to complete the task, but those with less REM sleep gave up more easily. “This suggests that REM sleep in horses is associated with motivation and perseverance,”
Dr. Hämäläinen explained.

No external signs of sleep disturbances were observed in the study, although some of the horses exhibited little REM sleep. The results nevertheless indicate that short REM sleep can affect equine performance, particularly when the task requires prolonged concentration and flexible thinking.

“While the horses were quick to learn simple tasks, the effects of short REM sleep periods started to show in longer and more demanding tasks,” Dr. Hämäläinen said.

“The findings offer a new tool for assessing the learning capacity and welfare of horses. They also emphasize the importance of sleep as part of their overall well-being,” said doctoral researcher Iina Brotherus, who studies equine sleep.

The study showed that coping in horses is not solely about training or motivation. The quality of sleep can also determine how effectively horses learn and tackle everyday challenges, they said. MeV

FOR MORE INFORMATION
Hämäläinen MJ, Brotherus IL, Wigren HKM, et al. Effect of horse sleep behavior on performance in a field-side spatial reversal learning test. Sci Rep. 2026;16:4265.