"Out of sight, out of mind"

We notice the presence of something many many orders of magnitude more strongly than the absence.

The absence is easy to forget about.

You have to maintain a mental model of the now-hidden thing, and keep refreshing that memory or it evaporates from your awareness.

The presence is much harder to forget about--it's right there, you can see it with your own eyes!

Each time your eyes pass over it it reminds you it exists.

One of the ways we think larger thoughts than our mind can handle is by caching partial computations in the world around us, ready to be pulled right back in in a moment by our eyes.

A form of stigmergy.

Our working memory is like the register file.

Our memory is like RAM.

The objects we create in the world (e.g. things we write down) are storage on disk.