Pareidolia
Pareidolia is seeing meaningful images or hearing meaningful sounds, especially faces and voices, in random or vague input. It comes from a brain tuned to detect faces quickly, even at the cost of false alarms.
In everyday life
People see a face in the front of a car, in an electrical outlet, or on the surface of the moon.
Staring at a water stain on your ceiling, you clearly see the outline of a smiling old man, and once you have seen him you can't stop seeing him.
Why your mind does this
Our ancestors survived by spotting patterns fast: rustling grass might mean a predator, and dark clouds meant rain. Filling gaps with a plausible story lets us act on thin information instead of freezing. A brain that sometimes sees a pattern that isn't there loses less than one that misses a real threat.
Its family, in 30 seconds: Stories & patterns
How to spot it
Ask whether the shape or message you perceive would still be there if your brain were not searching for it.
How to counter it
Show the image or play the sound to someone else without saying what you noticed, and see if they find it on their own.
Same family: Stories & patterns
SourcesWardle et al. (2020)·Wikipedia