The function of the dreams is not known and, just like sleep, it probably plays multiple functions and works at many different levels, both individual and collective. It is thought that it plays functions in learning and memory, in training for dangerous situations, in emotional rehabilitation and in the identity of the species – which means that by dreaming similar things in general, we would assume our human specificity. However, some authors consider it to be an epiphenomenon with no specific functions or, at most, a movie which we would watch every night for free to have fun. The fact that we do not remember our dreams generally means that we have slept well, since, in order to remember your dreams we need to wake up. People with more diffuse and “dreamy” personality tend to dream more than a structured and concrete personality.
In sleep laboratory, when waking up people at different times of the night, the evocation of dreams arises in 90% to 95% of cases. The likelihood of remembering dreams occurred in REM is greater than for the dreams occurred in NREM. Dreams will vary throughout the night; they incorporate a greater amount day’s residues at the beginning and at the end they contain more fantasy elements. The dominant material is our daily routine, sprinkled of old memories, all rearranged so that each dreamer produces a single sequence, of which he is simultaneously producer, lead actor and spectator. The emotions expressed in dreams are basic positive and negative emotions such as fear, anger, quarrel, annoyance, guilt and joy, contentment, delight, elation, etc.