Tetris effect

The Tetris effect (also known as Tetris Syndrome) occurs when people devote so much time and attention to an activity that it begins to pattern their thoughts, mental images, and dreams. It takes its name from the video game Tetris.

People who played Tetris for a prolonged amount of time could find themselves thinking about ways different shapes in the real world can fit together, such as the boxes on a supermarket shelf, the buildings on a street, or hallucinating pieces being generated and falling into place on an invisible layout. In this sense, the Tetris effect is a form of habit. They might also dream about falling tetrominos when drifting off to sleep or see images of falling tetrominos at the edges of their visual fields or when they close their eyes. In this sense, the Tetris effect is a form of hypnagogic imagery.

The Tetris effect can occur with other video games. It has also been known to occur with non-video games, such as the illusion of curved lines after doing a jigsaw puzzle, or the involuntary mental visualisation of Rubik's Cube algorithms common amongst speedcubers.

On a perceptual level, sea legs are a kind of Tetris effect. A person newly on land after spending long periods at sea may sense illusory rocking motion, having become accustomed to the constant work of adjusting to the boat making such movements (see "Illusions of self-motion" and "Mal de debarquement"). The poem "Boots" by Rudyard Kipling describes the effect, resulting from repetitive visual experience during a route march:

’Tain’t—so—bad—by—day because o’ company,

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