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Book Summary: The Book of Humans: A Brief History of Culture, Sex, War and the Evolution of Us

Author: Adam Rutherford

Substory: Mirror Test

Another part of this complete cognitive package is not just knowing others, but knowing yourself. Recognition that you are an individual with agency and self-determination. The mirror test is a standard of ethology nowadays. Can you recognise that the image reflected from a mirror is not a moving picture or someone mimicking your actions, but is actually you? It’s designed to test the ability of an organism to be visually self-aware. In some versions of the test, you spot a bit of dye on the forehead of the participant, without them knowing, and see if they try to touch their own heads where the dot is. This way, they are recognising that the mark on the individual in the mirror is in reality on their own head. By the time human children are about two years old, they will direct their hands to the dot on their head. If you have a baby, this is a fun and easy experiment to do from six months old.

A few animals have also passed this test, to much acclaim. Bottlenose dolphins and killer whales appear to pass, sea lions do not. Three elephants have been tested by placing a red cross on their heads, not visible without a mirror, and of those, only one, called Happy, acknowledged and repeatedly tried to touch the spot with her trunk.1 Of the super-smart birds, so far only a single magpie has shown any ability to recognise that the reflection is their own body.

I wonder how significant mirrors are in the grand scheme of cognitive evolution. Certainly, this test shows a level of thinking that relates an abstraction to reality – ‘that is me, but it is also not actually me’ but it’s a strange sort of test from which to extrapolate huge inferences. It tests visual recognition, when many organisms don’t primarily rely on sight for sensory input. Surely a dog would be better off doing some sort of smell-mirror test? Also, it’s testing an artifice. Animals presumably can see and detect parts of their own body, in the full absence of mirrors in their lived experience. Does that make them somehow quantitatively less self-aware than us? I don’t think it does. Gorillas don’t pass, though maybe ones in captivity with a lot of human familiarity might. Then again, eye contact is generally a sign of extreme aggression in gorillas, so maybe getting them to spend time staring at an image of a gorilla is not reflective of their cognitive capabilities. In 1980, the psychologist B. F. Skinner also challenged the significance of the mirror test by intensively training pigeons to pass it. Bribed with food, the pigeons were shown dots that they first had to twist their heads to see, and second, they could see in the mirror. After a few days’ training, the pigeons would identify spots on their own bodies, by only looking at the mirror. They had learnt to pass the mirror test, for a handful of seeds.

I’m not saying that the mirror test is invalid; it’s more that being self-aware is certainly a facet of a high-cognition mind, but there are many ways to be self-aware other than clocking oneself in a looking glass. It’s quite an anthropocentric test, as it relies on the assumption that being able to see oneself in a mirror is an important symptom of a state of mind. Toads spend a lot of time sitting very still after reversing into damp holes, but we don’t consider that fortitude of endurance to be a neuroscientific benchmark of any sort, even though it’s clearly important to the toad. We talk of the traditional five senses, but in reality, there are many more than that. Proprioception is a significant one here – awareness of one’s own body in space; another is interoception – an awareness of one’s internal bodily state: try sitting perfectly still (like a toad) and counting your heartbeats by nothing other than feeling them in your body. These are also key expressions of a sense that you are a body in space, independent of the environment.

Self-awareness is essential for recognising that you are a being which is separate from everything else. It is part of the conscious experience of being human, and the experience of being in some other animals.