Horses can be tricky creatures, and even the most tolerant rider will occasionally yield to the temptation to give their mount a ticking off and a stern look.

But, according to groundbreaking new research, they really shouldn’t: the horse may bear a grudge.

Scientists at the Universities of Sussex and Portsmouth have established that horses can not only read emotions, but can then remember the emotional expression of humans.

Published in the journal Current Biology, the discovery is the first example of its kind among mammals and sheds new light on the intelligence of the species.

The research team conducted controlled experiments whereby domestic horses were presented with a photograph of an angry or happy human face.

Several hours later the animals saw the person depicted in the photograph, then in an emotionally neutral state.

Even the short-term exposure to the photograph was found enough to generate clear differences in the subsequent reaction of the horse when it saw the human in the flesh.

The scientists noted that, despite the human being in an an emotionally neutral state during the live meeting, the horses’ direction of gaze differed depending on whether the person had been depicted as happy or angry.