Why do we dream?

Your sleeping brain casts your old maths teacher as a hotel receptionist, loses your suitcase and insists the lift is a submarine. In the morning you are expected to make breakfast as though nothing unusual happened. The production budget is extraordinary. The script supervision could use work.

Sleep is not a single off switch. We cycle through non-REM and REM phases, with measurable changes in brain activity and physiology. During REM, the brain is active and most muscles normally become limp; vivid dreaming is closely associated with this phase. A busy sleeping brain is therefore not a contradiction. ^[1]

But finding the conditions in which an experience occurs is different from discovering its purpose. A stadium tells us where a match happens; it does not explain why humans invented football. Likewise, knowing about REM does not establish that every dream has a hidden message or one evolutionary job.

An intriguing proposal borrows from machine learning. Erik Hoel’s ‘overfitted brain’ hypothesis suggests that strange dream experiences might help brains avoid becoming too narrowly fitted to familiar waking patterns. In machine learning, a model can memorize training examples yet struggle with new situations. Adding variation can help it generalize. Hoel proposes a possible parallel in dreaming. ^[2]

That is a hypothesis, not a demonstrated diagnosis of last night’s flying refrigerator. A comparison with an artificial network can suggest experiments without proving that biological brains work in the same way. It is useful precisely when it generates questions we can test, not merely a clever sentence we want to believe.

Here is the wider twist: a dream can be personally meaningful without being a prediction. A song can bring an old grief to the surface without providing news from the future. Similarly, an image in a dream may invite reflection on your concerns without acting as an instruction from outside your mind.

Religious or spiritual interpretations add another layer. Someone may understand a dream as a visitation or guidance. Science can investigate aspects of the experience and proposed mechanisms; the emotional force of a dream alone does not verify an external messenger. Nor is ridicule an explanation. A gentle question often gets further than a triumphant dismissal.

We should be cautious with universal decoding manuals. Before announcing what a staircase means, ask what that staircase means to the person who dreamed it. Even then, interpretation is a conversation, not a recovered laboratory result. Sometimes the most honest answer is that the image remains puzzling.

The joy is that uncertainty does not make dreams worthless. They are part of human experience: funny, frightening, tender and occasionally very poor at continuity. We can study their biology, entertain competing explanations and enjoy the imaginative chaos without appointing every dream an oracle. Your brain may be exploring something. It may also have misplaced the hotel.