We often perceive a series of dots on a printed form as a solid line because of the gestalt principle of

Principle of closure

Explanation:

Principle of closure according to gestalt is the perception of completing a sequence of figures or objects if they are grouped together even when they are not complete

nigger, that word was originated for white folks   to keep black people under

and when black people use it, they know that's just how they greet each other

and when white folks use it, they know there's a double meaning under

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