Here’s what Professor Hallux has to say:
The human brain is a very mysterious thing. Most people dream, even if they can’t remember them. We know this because scientists have tracked the brainwaves of loads of people when they’re sleeping and it’s normal to have a long period of REM – that’s “Rapid Eye Movement” which shows their brains are busy doing something.
One idea is that dreams are a way of processing and filing away all the sights, smells, sounds, tastes and events of the day. Perhaps your brain works out which parts to remember and which to forget. If you have a problem, sometimes dreams can appear to reflect what’s going on – so if you have a music exam and are a bit worried, you might dream about being chased by pianos.
Others think dreams are made of much more random collections of thoughts caused by the brain randomly firing as you sleep. So if you’ve had a really weird dream about the sea made of jelly, well maybe that’s the reason.