perception

Your brain fills in gaps to create complete objects.

The Law of Closure describes how the mind perceives incomplete figures as complete, coherent wholes.

This perceptual grouping occurs based on visual structure and regularity rather than the requirement that the figure be a 'familiar' shape.

You are not seeing what is there; you are seeing what you expect to be there.

Where this comes from

Study: Gestalt psychology, Law of Closure
What the check found: Closure is a structural principle of visual grouping; it does not require the object to be familiar, only for the visual input to suggest a closed form via regularity, proximity, or continuity.
Confidence: Solid, with limits

One of these every day, and every one names the study it came from. When a finding is contested, it says so.