Few species are capable of recognizing themselves in a mirror. Many species interpret the image in the mirror as that of a conspecific. Being able to form a concept of ‘self’ requires higher mental ability. Do horses have this ability?
There are three stages an animal has to pass in a mirror self recognition test before the final stage of testing where a mark is applied to the animal in a region only visible with the help of a mirror to see if the animal attempts to remove the mark. Prior to this, the animal must show social responses towards the mirror. Then the animal explores the mirror, including looking behind it. Finally, to get to the stage of testing involving the mark, the animal must repeatedly test the mirror by looking at parts of its body that it cannot typically see without the mirror, or performing repetitive behaviours such as sticking out the tongue or moving in and out of the mirror’s range like playing peek-a-boo.
A few years ago there was an open access pilot study (https://doi.org/10.1371/journal.pone.0176717) using four horses and a large mirror to see if the horses would pass these four stages and recognize that it was themselves reflected in the mirror. At that point, the results were inconclusive, with horses recognizing that the reflected image did not behave like another horse but showing inconclusive behaviours for the remaining parts of the test.
More recently another open access study was conducted (https://doi.org/10.1007/s10071-021-01502-7) with more horses and different results. The mark was only used on the 11 horses (out of 14) that passed the first three stages of the testing as described above. A sham mark was used to ensure the horses were not detecting the mark through tactile means instead of actually seeing the coloured mark, and indeed most of the horses scratched more at the coloured mark than at the invisible one.
These results suggest that horses can develop an idea of self after some exploration of a mirror to satisfy themselves that it is not a conspecific. It is also possible that they recognized the mark on the face as unnatural and attempted to intentionally remove it.
Unfortunately, some reporters are touting this preliminary study with the headline that ‘horses worry about their looks,’ which is a sensational and inaccurate portrayal of the study results. Horses have previously been shown to be incapable of worrying about future events. Anxiety and stress are only triggered by context-specific memory. Reading the studies themselves, which are freely available, is much more accurate than reading reporters’ interpretations!
So don’t take my word for it either. Do some digging yourself, read the articles, and comment your thoughts and findings!