The strange-face-in-the-mirror illusion

It's strange to refer to it as "never seen before" since I'm in my 50's and knew about this in my childhood. There was nary a birthday party without this playing out at least once.

Some people refer to it as Bloody Mary. There are a lot of different stories to go with it, but in all cases, you basically stare at yourself in a mirror with the lights dim (typically a candle, for the mood). Eventually since you don't move your eyes, your eye saccades become inhibited enough that things black out except for a few details.

Those few remaining details tend to look like other people's / demon's faces. Your brain has a weird way of "filling in the blanks" when it needs to. It is famously frightening to children and people who believe in ghosts.

That's it. This has been known and regularly documented for a very long time.

Here's the wikipedia article on this very phenomenon, with artwork from the early 1900's describing it. https://en.wikipedia.org/wiki/Bloody_Mary_(folklore)

The history actually goes a lot farther back than that. https://en.wikipedia.org/wiki/Catoptromancy

The main physiological explanation is that we only that there is only a very small area that we can see clearly. Our brain reconstructs that information to give us the illusion that we see a much larger area. We can only do this somewhat reliably because we normally constantly move our eyes. A second cause is that that our eyes do not respond well to a constant stimulus. If you could keep your eye in a constant position after a while you would not see any constant image.

PDF of Caputo's 2010 original article on the subject (2 pages)

https://www.researchgate.net/profile/Giovanni-Caputo-4/publi...

I wonder if this effect is related to the "distorted face" effect seen in this video [0] in which rapidly changing images of faces creates very strange and distorted faces almost as an optical illusion.

[0] https://youtu.be/VT9i99D_9gI