On the most basic level, the author is using physical space to offload facts and ideas. He need not keep mentally aloft these pieces of information or the complex structure in which they are embedded; his posted outline holds them at the ready, granting him more mental resources to think about that same material. Keeping a thought in mind—while also doing things to and with that thought—is a cognitively taxing activity. We put part of this mental burden down when we delegate the representation of the information to physical space, something like jotting down a phone number instead of having to
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