Why do we Dream?

It is said that Bram Stoker dreamt his Dracula, as did Mary Shelley her Frankenstein, Robert Louis Stevenson his Dr. Jekyll and Mr. Hyde, and even Paul McCartney his Yesterday. And yet, despite all the reflections, theories and experiments on an issue that has fascinated human beings since time immemorial, the short answer to the question “why do we dream?” today continues to be this: we do not know. “If only we knew!” says Ursula Voss, a neuropsychologist at the Goethe University in Frankfurt (Germany).

Researchers try to figure out if dreams have a function. Credit: Jordan Whitt

Researchers try to figure out if dreams have a function. Credit: Jordan Whitt

In the 21st century, we no longer believe, as in antiquity, that dreams have a supernatural nature. But oddly enough, and despite all the accumulated science, it is hard to eliminate their prophetic interpretation. For example, a 2009 study found that many participants in a poll would tend to cancel a flight if they dreamt the plane crashed the night before.

Given the intense and sometimes strange nature of the dream experience, it is natural that the human being has tried from ancient times to explain dreams. This search found its first scientific analysis at the end of the 19th century thanks to Sigmund Freud. The Interpretation of Dreams (1899) is a historical bestseller from which many readers have sought symbolic explanations for their dreams and nightmares. But the Austrian psychoanalyst’s text is not a dictionary of interpretation, but rather the long explanation of the thesis that dreams are manifestations of desires of the subconscious, an idea already noted centuries earlier by Aristotle and Plato.

Dreams appear in the REM phase

The influence of Freud’s work lasted for much of the twentieth century. However, already in his time there was another current, promoted by medical authors, who sought an interpretation of dreams more biological than psychological. In the 1950s it was discovered that dreams appeared linked to a phase characterized by high brain activity and rapid eye movements (REM). The advance of neurosciences allowed the study of dreams to be undertaken from a more organic approach, and in 1977 the psychiatrists from the University of Harvard Allan Hobson and Robert McCarley proposed a neurobiological theory of the dreams called activation-synthesis hypothesis.

Dreams appeared in the phase REM, characterized by high brain activity. Credit: Nomao Saeki

Dreams appeared in the phase REM, characterized by high brain activity. Credit: Nomao Saeki

Hobson and McCarley described dreams as a consequence of the spontaneous activation of a primitive region of the brain, the brainstem, during the REM phase. When the cerebral cortex, where higher thinking resides, receives this kind of random neuronal noise, it tries to convert it into something that makes sense, and it does so by pulling from our personal archive of images and experiences. It is in this process of “synthesis” when the narrative of the dream appears. However, since during the process our mind shuffles the archive depending on these unrelated bursts, the results may be aberrant. In the theory of activation-synthesis, this is the origin of the sometimes bizarre and absurd nature of our dream-like adventures.

But the Hobson-McCarley model did not settle the question and later discoveries have provided new data that make it difficult to fit all the pieces together. Today we know that other mammals, birds and reptiles share the REM phase with us, but also that our dreams are not confined to this stage alone. Moreover, dreams are not usually as dominated by surrealism as we think. According to researcher G. William Domhoff of the University of California, Santa Cruz (USA), the conclusion of more than five decades of recording dreams is that the world of our dreams is more like everyday life than Alice’s Wonderland, and it maintains a certain regularity and consistency, even with our thoughts during the day.

Dreams are involved in memory consolidation

On the other hand, research reveals that dreams are involved in memory consolidation, transferring what is learned from the hippocampus to the cerebral cortex and relating it to our catalogue of emotions. These observations would fit with the idea that dreams can have an adaptive biological function; traditionally the capacity to dream has been considered as a mechanism of psychological hygiene, necessary to maintain a healthy mind. But according to Domhoff, this framework is shaken by two facts: dreams do not appear in their full adult form until the end of childhood, and there are even a small percentage of adults who never dream.

En el siglo XXI ya no creemos, como en la antigüedad, que los sueños tengan un carácter sobrenatural. Crédito: Edi Weissmann

En el siglo XXI ya no creemos, como en la antigüedad, que los sueños tengan un carácter sobrenatural. Crédito: Edi Weissmann

So, do dreams have a function, or do they not? Do they have a meaning, or do they not? Is there any way to reconcile the opposite ends of Freud and Hobson-McCarley? Researchers try to fit all the pieces into the same puzzle, a difficult task as there may not actually be a true essential biological function to the act of dreaming. And while dreams may not generally hide intentional messages from our subconscious as Freud argued, they are probably not like the noise from haphazard firing: “I don’t think it’s justifiable to say that dreams are based on random brain noise,” Voss says.

According to the neuropsychologist, who has conducted research in collaboration with Hobson, dreams may be a by-product of a sort of nocturnal update of the brain, when the input of information from the outside is minimal. When the brain tries to interpret this activity, it does not do so like someone searching for dragons in the shapes of clouds, but rather “we form associations between new and old information, tie it to emotion and store it in visual images,” she continues. In this way, dreams end up having a certain psychological meaning related to our motivations and concerns, our personal seal. “It is something like understood emotion,” adds Voss. “It does not carry a message, but it allows us to be introspective.”

However, Voss clarifies that for the moment this model is only a proposal, “not yet scientifically proven.” “But I’m certain that several other laboratories are pursuing very similar ideas,” she concludes.

Javier Yanes