Why do we dream?

Dreams take us everywhere, from a happy scene at home to a terrifying nightmare on another planet. But do our dreams and nightmares have any purpose? Did they pose an evolutionary advantage in the early stages of human development? The fields of evolutionary psychology and neuroscience of dreaming looks at the functionality of dreaming: did our ancestors who dreamed have a selective advantage over other individuals? Were then better adapted to their environment and able to pass on their traits as a result of dreaming?

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Many psychologists are inclined to believe that dreams have no purpose. Dreams could simply be the result of random cortical activation that occurs while we sleep. Studying dreams in an empirical manner is difficult: we cannot assign dreams to subjects or experience what they experience in a dream. Furthermore, in studying dreams we often must interfere with sleep, which could alter the dreams. So scientists attempt to measure around these roadblocks, which can be difficult. Thus, many psychologists are unwilling to accept any theories on the purpose of dreaming, because these theories are difficult if not impossible to adequately test.

Despite a resistance to believing dreams have a purpose, there exists a large literature exploring dreaming and its function. In the literature, there are a few better-known theories explaining what function dreams might serve. Threat-simulation theory posits that dreams allow us to practice threatening situations, so that if they do arise in real life, we have already thought out our response. Activation-synthesis theory looks at dreams as the product of random activity in the brain that comes to our awareness while we sleep. The cognitive theory of dreams discusses how dreams may aid cognitive functions, such as problem-solving and forming memories. These theories are all described in greater detail on subsequent pages.

Examples of some popular theories the functionality of dreams:

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Whether or not we will ever fully understand why we dream remains to be seen. Dreams are deeply connected to consciousness, and reside in the "hard problem" of neuroscience: that we can never truly understand another individual's experience. Nonetheless, we can explore fascinating theories that attempt to explain the incredible phenomenon that carries us to other worlds as we sleep.

This page on the function of dreams was written by Ruth Berman, an undergraduate student at Macalester College.