These stimuli "invoke attention modestly, allowing focused-attention mechanisms a chance to replenish." Put another way, when walking through nature, you're freed from having to direct your attention, as there are few challenges to navigate {like crowded street crossings}, and experience enough interesting stimuli to keep your mind sufficiently occupied to avoid the need to actively aim your attention. This state allows your directed attention resources time to replenish. After fifty minutes of such replenishment, the subjects enjoyed a boost in their concentration.
( Cal Newport )
[ Deep Work: Rules for Focused ]
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