Why do we dream?
Theory 1: Dreams express inner wishes and desires (Freud’s idea). But what about nightmares? Those can’t be wishes.

Theory 2: Dreams provide solutions to problems. But then why can we only recall 1% of dreams? Dreams aren’t helpful in providing solutions if we can’t remember them. Often anecdotes about people who “slept on” an issue and then created a solution after dreaming about it got the inspiration from the dream but then came up with the solution when they were awake. Also, this explanation doesn’t explain why we have disturbing dreams.

Theory 3: Dreams allow us to mentally re-file each day’s experiences and clear memories from the day.
But only half of dreams pertain to daily events. And if this hypothesis were true, what explains recurring dreams?

Theory 4: Dreams facilitate memory consolidation. New things learned during the day are reinforced by the firing of the new neuronal connections at night. But people don’t generally dream about a task they learned.

Theory 5: Dreams occur when specific neuron networks are activated. This is evidenced by neurocognitive research showing that during sleep neural activity only decreases by 10%. Without the neuron connections constantly firing, connections may degenerate. And thus, dreams are non-functional side effects of activation of networks that need to be activated to help keep the brain intact. This is psychology researcher’s current understanding (as of 2006).

Do our dreams have hidden messages?
According to the current theory (Theory 5 above) our dreams are “non-functional,” meaning they are random thoughts that do not contain any meaning. However, researchers have been struggling to understand why we have dreams for some time now, so who knows what Theory 6 may suggest in the coming years.

Note: these ideas may be out of date because they’re based off a 2006 lecture by Duke University professor Dr. Kevin Weinfurt in his class Intro to Psychology.