Why Do We Dream?

Step 1 of 5

Sleep runs in repeating cycles.

Roughly every ninety minutes you pass through light sleep, deep sleep and a strange active stage. Vivid dreams cluster in that last one.

Step 2 of 5

In the dreaming stage the body is locked.

Your eyes dart about and your brain lights up almost like waking, but the muscles are switched off so you do not act out the dream.

Step 3 of 5

Memories get sorted while you are away.

Fresh experiences are replayed and the useful parts are filed with older memories. People who sleep after learning remember more of it.

Step 4 of 5

Dreams are strange because the fact-checker is quiet.

The parts that ask whether something makes sense are far less active. The story-making parts carry on without anyone questioning them.

Step 5 of 5

You forget most of them within minutes.

The machinery that writes memories down is barely running during a dream. Only dreams you wake up inside tend to survive at all.

Everybody dreams, including people who insist they never do. They simply wake at a point where nothing was saved.