Although the existence of dreams is a psychological reality, they typically defy direct observation.  It should come as no surprise that because their realm is characteristically alien to our waking life, our memory for them is particularly fragile.  The frequent elusiveness of dreams presents a formidable challenge to our memory.

Dreams seem to elude direct observation because when we are dreaming it is unusual for us to realize that we are doing so.  When we do realize, we often respond to these unusual and particularly lucid dreams by an almost reverential appreciation.  It is generally believed that by “awakening” to the dream, the dreamer is allowed to explore the mysteries of the dream realm and perhaps attain an enlightening experience of the paradoxical complementarity of reality and illusion.  For most of us, however, the occasional realization that “this is only a dream” is quickly followed by waking up from sleep.  Thus, since we usually find dreaming to be incompatible with consciousness of dreaming, we generally have access to our dreams only after they have left us.  Consequently, our knowledge of dreams usually comes to us secondhand, from our recollection after awakening.

Awakening from a dream can be itself a rather puzzling experience, for the compelling reality of a vivid dream experience stands in bewildering contrast to the subsequent discovery that we have been actually lying in bed.  The psychological reality of our dream experience can oppose the apparent reality of our daytime existence in such a way as to arouse our curiousity.  There is a fable that expresses a metaphysical appreciation of this ambiguity.

“Chuang Tzu dreamed that he was a butterfly.  Since in his dream he did not know that he was anything else but a butterfly, he was happy and content to flutter from flower to flower.  Later, he awoke to discover that he was not a butterfly, but rather Chuang Tzu.  But he was perplexed.  “Am I really Chuang Tzu who dreamed he was a butterfly, or am I a butterfly who is now dreaming that he is Chuang Tzu?”  The moral given is that there is a natural barrier between man and the butterfly: the transition between the two is what is meant by metempsychosis, that is, the transmigration of souls.”

An adept in the art of Tibetan yoga is said to be able consciously to experience this transition.  He attempts to maintain continuous consciousness while progressing from the state of wakefulness to falling asleep, then to dreaming and finally to re-awakening.  Most of us, however, do not experience this underlying unity.  We are accustomed to having our conscious existence interrupted by sleep.  And when we awaken, we immediately reconnect quite naturally with our daily reality.

As we arise to confront the duties of the day, we can usually dismiss easily any lingering dream fragments as if they were meaningless fancies of a sleeping mind.  Dreams invite such neglect for they usually appear discontinuous with each other and alien to our waking life.  No wonder, then, that the dream is often rejected as incoherent nonsense and that it slips from our memory as we engage ourselves in the day’s activities.  Our memory system is not designed to retain nonsense.  Being already overworked, it has little time to digest the strange forms of dreams, especially when they seem irrelevant to the needs and purposes of the day.

A more technical explanation of how dreams are forgotten is provided by experimental laboratory techniques which have been devised to observe the potential dreamer during sleep.  Through the use of electronic instruments which monitor the bodily processes of the sleeper, it has been discovered that sleep passes through cyclical stages.  About every ninety minutes the sleeper’s brain-wave activity approaches that of wakefulness.  The irregularity of the pulse and respiration suggests emotional arousal.  Behind closed lids the eyes are moving rapidly as if observing some ongoing action.  If the sleeper is awakened at this point, the person will usually report having been dreaming.

The discovery that dreaming occurs periodically through the night and that it is associated with a particular stage of sleep has significantly intensified the investigation of dreams.  It is now generally acknowledged that if the sleeper is awakened immediately following the active stage of sleep, the person can usually recall a dream.  However, this ability declines rapidly as the awakening is delayed.  Consequently, in the morning the dreamer will have some difficulty in recalling the dreams he reported during the previous night.  This indicates that we forget dreams not only after we awaken but also while we sleep.

People who complain that they never dream have been invited to sleep in laboratories.  There the dreams are extracted during the night and in the morning the dreamers are presented with their recorded reports.  It is clear, then, that when we awaken in the morning without a dream it is because we have forgotten.

Apparently the mind never sleeps, for when sleepers are awakened from other than the dream state, they will usually report that something was going on in their minds.  Sometimes they will report that they were dreaming, but not so frequently as when they are awakened from the dream state of sleep.  More often they will say that they were “thinking”.  This reported thinking activity resembles normal thought and typically relates directly to the sleeper’s daytime concerns.

Why is it, then, that although we have been mentally active throughout the night, we are experiencing our awakening as the emergence from unconscious sleep?  Why should we be able occasionally to recall some of our dreaming but typically none of our thinking?  This discrepancy is puzzling, since during the night we spend much more time thinking than we do dreaming.  Moreover, the quality of our nocturnal thinking is perfectly compatible with that of our waking thought, whereas the quality of our dreaming is quite the contrary.

When we look for the factor that favour dreams and that affords them some tentative privilege to our memory, we find that it is the activation that is present during the dream stage of sleep.  The dream state has been called activated or paradoxical sleep because of its resemblance to a waking state.  It is, in some sense, a partial awakening.  It is a psychological principle that a certain degree of arousal is necessary if we are to register something into memory.  The arousal that occurs during the dream state – and it is absent during the other stages of sleep – is the probable basis for whatever ability we have to remember our dreams.