Do 18-month-olds recognise themselves in a mirror?

Nisha Matthews

If you have ever sat a baby in front of a mirror, you know that they tend to get  pretty excited and often make faces, talk to, and poke at their reflection in the glass.  The question is, do they understand  that they are looking at a reflection of their own image? Early developmental research used a “mirror test” to measure self recognition. In this task, researchers put a red spot on the baby’s nose and then code their reactions when they are placed in front of a mirror. The logic is if the baby understands that the baby they are looking at in the mirror is themselves, they will try and rub the spot off their nose. You can try this at home;  on average, about half of 18-month olds will try to rub the spot off their face.

The mirror test has come under fire though, because much of the research has been conducted with infants from WEIRD (White, Educated, Industrialised, Rich, Democratic) countries. Older infants and children in rural, non-Western cultures do not consistently react in the same way as so called “WEIRD” babies to the spot on their nose when they see themselves in a mirror. For example, a 2011 study published in the Journal of Cross Cultural Psychology found that only 2 of the 82 Kenyan children in the study aged between 18 and 72 months  “passed” the mirror test. These results suggest that the mirror test might be measuring more about experience with mirrors, than self-recognition per se.

Given these limitations, researchers have started to look at other ways of assessing self-recognition in babies, including measuring the changes in the electrical activity produced by the brain when infants look at faces.

Researchers from the Donders Institute for Brain, Cognition and Behaviour in the Netherlands used electroencephalogram (or EEG) to measure infants’ brain activity while 18 month old infants looked at pictures of their own face, the face of another infant, their parent and an unfamiliar person. For 13 of the 18 infants tested, the brain responses were bigger when babies looked at a picture of themselves relative to when they looked at a picture of another infant’s face.  

Researcher also tested the same group of babies on the the mirror test, and much like previous research, showed that about half the babies noticed the red mark on their face and touched it.  If the mirror test and the brain response measures are both indexing infants’ ability to recognise themselves in the mirror, we might expect that only those who pass the mirror test would show the differential brain response. However, when researchers compared the brain responses of the babies who passed the mirror test and those who did not there was no significant difference in the brain activity of the two groups.

This research suggests that most babies have the capacity to recognise their own image and distinguish it from images of other people as early as 18 months, however, only half of them will respond to their reflection in the mirror by touching the mark on their face.  By measuring more than just behaviour, new tools such as EEG give more nuanced insight into complex phenomenon like self recognition.
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The mirror test is still fun and you should give it a go at home. Don’t worry if your 18-month old doesn’t rub off the spot though. This research suggests that they understand that the face in the mirror is their own, they just don’t care that their nose looks funny. ​