Why we forget most dreams

Most nights hold several periods of REM sleep, the stage richest in vivid dreams, and dreaming happens in other stages too. Yet on most mornings, what is left is a vague mood, a fragment, or nothing at all. Forgetting is not a sign that you did not dream. It is how dream memory normally works.

The dreams are there

When researchers wake people during the night in a sleep laboratory, dreams turn up again and again. Averaged across dozens of studies, about four in five awakenings from REM sleep produce a dream report. From non-REM sleep the figure is lower, but in more recent studies around half of awakenings still yield some kind of mental experience.^[1] So the gap between how much we dream and how much we remember is mostly a gap in memory.

A dream needs a moment of waking

In 1976, the psychologists Koulack and Goodenough proposed what is still the best-known explanation, the arousal-retrieval model.^[2] It has two parts.

• Arousal. The sleeping brain is poor at storing what happens during sleep itself. For a dream to be stored, it seems to need a period of wakefulness soon afterwards, while it is still fresh. Dreams we sleep straight through are mostly lost.
• Retrieval. Even a stored dream has to be found again in the morning. How striking the dream was, and how much else crowds in as soon as we wake, shape whether it can be recalled.

This is why the moment of waking matters so much. Waking during or just after REM sleep, which is longest towards morning, gives a dream its best chance. It is also why a nightmare, which wakes you, stays with you far more than a pleasant dream you slept through. We wrote about this in why nightmares cluster at 3 a.m.

High and low recallers

Some people remember a dream almost every morning; others hardly ever. A research group in Lyon has studied the difference. Earlier work had found that high recallers report waking more often during the night. In one of the Lyon studies, 18 high recallers and 18 low recallers had their brain activity recorded while first names were played among other sounds, once while they watched a silent film and once while they slept. The high recallers’ brains responded more strongly to the names in both states, including a response linked to shifting attention.^[3]

A second study from the same group used brain imaging. The high recallers, who remembered about five dreams a week on average, compared with about one every two weeks for the low recallers, showed more activity in two regions, the temporoparietal junction and the medial prefrontal cortex, both in sleep and at rest while awake. The authors suggest these areas may support dream imagery and memory, and that a brain more tuned to the outside world may wake briefly more often, giving dreams more chances to be stored.^[4]

Both studies are small, and both show differences between groups rather than what causes them. Still, they fit the arousal-retrieval idea: brief moments of waking seem to matter a great deal for what we remember.

What shapes your own recall

• How you wake. Lying still for a moment before the day rushes in gives a dream more chance; jumping straight into messages gives it less, because new thoughts crowd it out.^[2]
• How broken your sleep is. More awakenings in the night mean more chances to store a dream. In a study of 444 people, night-time awakenings were one of four factors linked to how often people recalled their dreams.^[5]
• How interested you are. A positive attitude towards dreams was another, along with personality traits such as openness to experience, and creativity. Together, though, the four factors explained only about 8 per cent of the differences between people, so no single one is decisive.^[5]
• Whether you write them down. Keeping a dream diary tends to increase how many dreams people remember.^[6]

If you have nightmares

If bad dreams are the problem, forgetting can sound like the solution. But remembering less is not a goal in itself, and nightmares are memorable by nature, because they wake you. What helps is changing them.

That is where a brief record is useful. Imagery rehearsal, the approach sleep medicine recommends for recurring nightmares, starts from a dream you can describe, and especially from the moment it turns.^[7] You do not need a full account. A line or two, written soon after waking, is enough to work with later, in daylight. Here is how imagery rehearsal works.

Keep the note short and plain, and stop if writing it down leaves you more unsettled. Because diaries tend to boost recall, more detail is not always better.^[6] The point is not to collect nightmares, but to catch one well enough to give it a different ending.

In Baku, a one-line note on the night is enough to start a rewrite later, when you are ready.