Experts said graffiti stopped people from daydreaming, and so was good at helping people focus on mundane tasks.

专家表示，涂鸦可以防止人们走神，并帮助他们专注于平凡的琐事。

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New York's recovery certainly started with a clampdown on anti-social behaviour graffiti writing, street drinking, turnstile jumping, and so on.

ECONOMIST: Crime

Knowing this, workers and visitors often take photographs of special bits of graffiti, so the words will live on.

WSJ: WTC workers scrawl graffiti of defiance, hope