Horses can tell you when they want a blanket – and when not

Some horses in Norway can tell you whether they want to wear a blanket or stick with bare backs, according to a new study.

The discovery is an important addition to understanding of horse smarts and learning abilities, according to researchers at the Norwegian Veterinary Institute. They taught 22 horses to use symbols to indicate their blanket-wearing preference - and the equines' easy mastery of the task suggests they understood that the symbols had meanings that led to outcomes.

''Our aim was … to develop a tool to 'ask' horses whether or not they prefer to wear a blanket under different weather conditions,'' the authors wrote in Applied Animal Behaviour Science. In the end, they added, ''Horses chose to stay without a blanket in nice weather, and they chose to have a blanket on when the weather was wet, windy and cold.''

More than a century ago, a German horse nicknamed Clever Hans became a celebrity in Europe for his whiz-like ability to answer complex math, reading and spelling questions by tapping his hoof. Today, he's an example of some of the pitfalls of scientific studies involving people and animals: Hans, it turned out, was stumped when his human testers didn't know the answer to the question - which meant he was actually clever at reading the unconscious cues of people.

Horse cognition research has come some way since then, and the animals have shown savvy at recognizing shapes and telling objects apart. But this task added another level.

The subjects were 23 ordinary riding horses with charming names including Poltergeist, Virvelvind and Romano (one horse died shortly after the training, leaving 22 in the end). All had previously experienced wearing blankets when their owners deemed it necessary. To help the horses express their own preferences, the researchers created three simple boards: One with a horizontal bar meant ''put blanket on''; an unmarked board meant ''no change''; and a board with a vertical bar meant ''take blanket off''.

Then the horses went through a methodical literacy course of sorts. First, the trainers introduced the symbols one at a time. Horses that touched it with their muzzles would be rewarded with a thin slice of carrot, and then the corresponding action would be carried out - the blanket taken on or off. Once the horses had that down, they were shown both symbols at the same time, but they only got their treats if they touched the ''relevant'' one. In other words, if a horse wearing a blanket touched the symbol that meant ''put a blanket on,'' he'd get nothing.

Next, the researchers introduced temperature to the equation. Horses were draped in thick blankets that made them sweaty and ''obviously hot'', or they were put outside in what the Norwegians called ''challenging weather'' - so it really must have been awful - until they tensed, tucked in their tails or showed other signs of being cold. They had to pick the relevant symbol 12 times to move onto the next step, which was meeting the blank ''no change'' board. Picking that one always earned a carrot, but never a blanket status change.

After that, the horses saw all three boards in various combinations and locations, and only relevant choices led to snacks. Then they were given a ''free choice'' between two relevant symbols.

But the ''ultimate test,'' the researchers wrote, was carried out in the elements - several variations of them over the course of nearly a year. And the horses nailed it, each and every one of them.

''In total, these results strongly indicate that the horses had learnt to communicate their preferences using symbols,'' the authors wrote.