Monkeys, when first shown a mirror, respond to the ‘intruder’ with hostility — teeth are bared, and war-like poses adopted. We, humans, recognise our own reflections in a mirror as ‘me’. However, this ability is not a uniquely human trait. The “Mirror test” is also passed by chimpanzees, dolphins, elephants, some birds and even fish.
The test for self-recognition is simple enough. A prominent mark (for example, a large red dot) is secretively made on the face of the subject, in a place where it is not visible to the subject. When placed on an infant or a small child, a red mark on the forehead certainly draws the attention of the child. Until they are about 18-months old, children reach out to try and touch that strange mark in the mirror. From around 18 months of age, children react to the reflection in a mirror by trying to touch the mark on their own foreheads. They seem to ask themselves, “How did this get to my face?”
The older child’s ability is surely a sign of self-recognition. But is it also a sign of self-awareness? After all, even grown-up humans have wide-ranging reactions to mirrors. Some cannot resist stopping, others do not seem to pay much attention to their reflections.
Self-recognition
New findings about mirror self-recognition have come from a Japanese laboratory, studying the bluestreak cleaner wrasse fish, which is known to show signs of self-recognition (Proceedings of the National Academy of Sciences). This small fish has a mutualistic relationship with larger fish in tropical oceans. It feeds on parasites attached to their bodies. The cleaner fish waits at chosen places, and the parasite-ridden fish present themselves for cleaning. They even adopt strange body postures so that the cleaner fish can get to the parasites. The scene resembles a barber’s shop, where men hold their chins, or their arms up for the barber to shave.
The experiments with cleaner fish were performed in aquariums, one fish at a time. A mirror is first placed in the water, or a photograph of the fish is shown on a screen. On the first few occasions, the image is attacked. But over time, self-recognition is attained, and this fish passes the mirror-test. It is aggressive only towards images of strangers. It even recognises bright marks painted on its body, and tries to rub them off on any nearby surface.
When shown a manipulated image, where the body of a stranger now carries the face of the fish, the fish does not show aggressive behaviour. But a photoshopped image with the face of a stranger on the fish’s body attracts hostility. The cleaner fish seems to have a memory of its face.
Self-awareness?
Returning to human children, we have seen that self-recognition is learnt as the child grows. Full recognition of the reflection in the mirror as ‘me’ occurs by the age of 18 months. This is also the age at which children begin to talk about themselves, and recall events from memory (for example, “I ate it”). Can this be called self-awareness?
(The article was written in collaboration with Sushil Chandani, who works in molecular modelling. sushilchandani@gmail.com)
dbala@lvpei.org
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