Can Magpies Recognize Themselves in a Mirror? The Test

What is the mirror test?

The mirror self-recognition test was developed by the American psychologist Gordon Gallup in 1970 with chimpanzees. It is often called the mark test.

First, an animal is allowed to get used to a mirror. Then a colored mark is placed on a part of its body that it cannot see directly, such as the forehead or throat. If the animal looks in the mirror and then touches, scratches or examines the mark on its own body, it seems to understand that the reflection shows itself rather than another animal.

Most animals never get that far. They treat their reflection as a stranger, displaying to it, attacking it or ignoring it. For decades only great apes clearly passed, and many scientists believed the ability needed a mammal’s layered neocortex.

The 2008 magpie study

In 2008, Helmut Prior, Ariane Schwarz and Onur Güntürkün of the Ruhr University Bochum in Germany published their magpie study in the journal PLoS Biology. They tested five hand-raised Eurasian magpies.

Each bird received a small colored sticker, yellow or red, on the black feathers of its throat. A magpie cannot see its own throat, except in a mirror. As a control, the birds were also tested with a black sticker that blended in with their feathers, and with a colored sticker but no mirror.

The results, as reported, were striking. Some of the birds with a colored mark repeatedly tried to reach it with their bill or scratched at it with a foot while a mirror was present, sometimes until the sticker came off. They hardly ever did this with a black mark or without a mirror. The researchers concluded that magpies understood the image in the mirror was themselves.

The study made headlines because birds have no neocortex. If magpies could recognize themselves, then self-recognition must have evolved separately in birds and mammals, an example of convergent evolution.

The 2020 replication

Good science depends on results being repeated. In 2020, a Spanish team led by Manuel Soler of the University of Granada published a replication in the Journal of Comparative Psychology. They followed the original method closely but tested a larger number of magpies.

They did not find the same result. Magpies touched or scratched at the marks about as often whether or not a mirror was present, which suggests the birds were reacting to the feel of the sticker rather than to what they saw in the mirror. The researchers stressed that their results did not disprove the 2008 study, but said the original evidence should be treated with caution.

Why might the studies differ? Possibilities include the small number of birds in each study, differences in the birds’ backgrounds and experience, the weight and placement of the stickers, and the difficulty of telling mark-directed scratching from normal preening. Small, single studies are easy to over-interpret, which is why repeated tests matter.

Which other animals pass the mirror test?

Some pigeons can pass a modified version after intensive training, but untrained pigeons do not. That difference is important: the classic test asks whether an animal recognizes itself spontaneously.

What the mirror test does and does not tell us

Passing the mirror test is strong evidence that an animal can link its reflection to its own body. Failing it does not prove an animal has no sense of self. The test depends on eyesight, on interest in a mark on the body and on the animal’s normal grooming habits. Animals that rely mostly on smell or hearing, or that simply do not care about a spot of color, may fail for reasons that have nothing to do with intelligence.

For this reason, many researchers now prefer to look at several kinds of evidence together, rather than treating the mirror test as a simple pass-or-fail measure of self-awareness.

How smart are magpies?

Whatever the mirror results, magpies are among the most intelligent birds. Their forebrain is large relative to their body size, they hide food and remember where they put it, and they move their caches when another bird is watching. In experiments, magpies and other corvids track hidden objects and solve problems that challenge many mammals.

Their relatives show similar skills, as explained in how smart are crows and ravens? and in the wider ranking of the smartest animals. The magpie’s reputation as a jewel thief, on the other hand, does not stand up to testing: see do magpies steal shiny things?