Only a few individual animals have recognised themselves in mirrors before.
If you ask people to list the most intelligent animals, they’ll name a few usual suspects. Chimpanzees, dolphins and elephants are often mentioned, as are crows, dogs and occasionally pigs. Horses don’t usually get a look in.
So it might come as a surprise that horses possess an unusual skill, widely considered an indicator of self-awareness. In a recent study, researchers have found horses can recognise their reflections in mirrors.
Animals looking at a mirror for the first time often respond socially – they act as if their reflection is another animal. After a while, this social response tends to subside. Some animals lose interest at this point, but others will go on to explore the mirror and investigate how they can make the reflection move using their own body.
Once animals have stopped responding socially, scientists test their understanding using the “mark test”. The animal is marked in a location they’ll only be able to see in the mirror, perhaps on their forehead or ear. Then scientists watch to see if the animal spends more time touching this body part in front of the mirror when it’s marked than when it isn’t. If it does, this suggests the animal recognises its reflection.
This test was first used to demonstrate self-recognition in chimpanzees in 1970, and scientists have since used versions of the test to look for self-recognition in many other species. The results suggest that self-recognition is rare. Among non-primates, only a few individual animals have passed the mark test, including four Bottlenose dolphins, two Eurasian magpies and an Asian elephant.
But a new study by researchers in Italy has found evidence of self-recognition in horses. Interestingly, the results suggest the ability is not just limited to a few clever individuals. While we should be cautious about generalising from a single study, this suggests self-recognition might exist in horses as a species.
In the study, a large mirror was placed in a horse training arena. Once horses got used to the mirror and stopped responding socially, the researchers used the mark test to look for self-recognition, comparing the horses’ behaviour in two conditions. In one condition, researchers drew a cross shape on both of their cheeks using a colourless ultrasound gel. In the other, they were marked in the same way but with a coloured ultrasound gel.
The important question was whether the horses would be more interested in the visible marks than the invisible ones. And they were. The horses spent around five times longer scratching their faces in front of the mirror when they were visibly marked.
The researchers concluded that they saw the marks in the mirror, understood that those marks were on their own faces, and were trying to remove them. They recognised their reflections.
The mark test is often described as a test for self-awareness. But whether that’s true is debatable, and depends on what we mean by self-awareness – a tricky philosophical question.
When we say that a person is self-aware, we often mean they [ … ]