Dream

A dream, in the psychological sense, is the set of images, scenes, ideas, emotions and sensations that the mind produces, almost always involuntarily, while a person sleeps. Although it is associated with the night, the phenomenon occurs during several stages of rest, and in adults it usually fills more than two hours per night, spread across episodes lasting from about five to twenty minutes.

Interest in dreams is as old as writing. In Mesopotamia and ancient Egypt, so-called visitation dreams were recorded, in which an authoritative figure, often a deity or an ancestor, instructed the dreamer to take specific actions or announced future events. Over time, dream interpretation became a practice present in many religious texts and the origin of various analytical traditions, eventually leading to modern psychotherapy. Sigmund Freud, in his work on the interpretation of dreams, regarded them as disguised fulfilments of repressed desires, while other authors have preferred to understand them as processes of elaborating experience, without a fixed hidden meaning.

Dreaming is closely tied to sleep. In adults, the night is organised into cycles of ninety to one hundred and twenty minutes that combine light sleep, deep sleep and rapid eye movement (REM) sleep. Dreams occur mostly in this last stage, in which brain activity resembles that of wakefulness, although they also appear in other stages, so the link between REM sleep and dreaming is not exclusive. Since dreams can only be studied through the person's account on waking, science cannot access the dream experience directly, which limits the testing of many hypotheses.

In terms of content, dreams often blend places, people and objects fluidly and frequently strangely, and they frequently reflect the dreamer's memories and concerns. Studies of large collections of reports, such as those carried out in the twentieth century by Calvin S. Hall, suggest that negative emotions such as anxiety or fear are more common than positive ones, and that there are patterns shared among people from different cultures. Collective events also leave a mark: some recent research has observed an increase in themes of fear and illness during the COVID-19 pandemic.

Today the debate centres on what dreams are for and where they originate in the brain. It is not known with certainty whether there is a single neurological origin or whether several regions are involved, and the ethical limits of research with human subjects make definitive answers difficult. For this reason, the study of dreams combines neurophysiology, psychology and philosophical reflection on consciousness.