Researchers are looking for a scientific answer to explain why children think they actually disappear when they cover their eyes while playing peekaboo.
Researchers led by James Russell at the University of Cambridge have carried out the first study into this bizarre trait with groups of three and four-year-old children.
The children's eyes were covered with masks and they were then asked whether they could be seen by the researchers - with most saying no.
Many also believed that the researchers could not see adults who were wearing eye masks - leading to the conclusion most young children believe that anyone who covers their eyes is obscured from other people's view.
The researchers then attempted to distinguish what exactly creates the feeling of invisibility - whether it was not being able to see at all or just because the other person couldn't see their eyes.
The children were given a pair of mirrored goggles so that while they could see through the glasses, no one could see their eyes.
Unfortunately, only 7 of the 37 participating children were able to get to grips with the idea that while they could still see, no one could see their eyes.
But of those who did understand the concept, six believed they were invisible if the researchers couldn't see their eyes, even if they could still see them.
Although when the children were asked to explain how they were made invisible by simply hiding their eyes, many knew that their bodies remained visible, suggesting a childhood distinction between their physical bodies and the 'self' they connect to their eyes.
To test this theory that children believe they can be seen only through their eyes, the researchers looked directly at each of the children while asking them to avert their gaze.
They then did the same process in reverse, with the children looking at the researchers while they diverted their eyes.
In each instance, the majority of children felt they were not being seen so long as their eyes didn't meet the other person's, giving some support to the ideology of eyes being the the window to the soul.