Why some people remember their dreams (and others don't)

Almost everyone dreams every night. Most adults have four or five distinct dream episodes per night, mostly during REM sleep but also during the deeper stages.

But only some people remember any of it. Some remember dreams almost every morning. Others go years without a single one. The difference is not really about who dreams more. It is about what happens to the dreams in the seconds after waking.

How dream memory works

Dreams are extraordinarily fragile. Even people with reliable dream recall lose their dreams quickly. If you are not actively trying to hold onto a dream within about 90 seconds of waking, it is usually gone.

This is because dream content lives in a kind of cognitive in-between state. It is rich, vivid, sometimes more emotionally intense than waking experience. But it is not encoded into long-term memory the way waking experiences are. The hippocampus, which normally tags experiences for storage, is functioning differently during sleep. Without help, dream content fades almost as fast as it formed.

What distinguishes high recallers

Research has identified some differences between high and low dream recallers:

• High recallers wake more often during the night, even briefly. Those moments of awakening let them catch a dream while it is still accessible.
• Their brains are more responsive to external stimuli during sleep. A 2014 study found that high recallers' brains responded more strongly to their own name during sleep, suggesting a different threshold for shifting between deep sleep and lighter awareness.
• They have slightly more activity in the temporo-parietal junction, a region involved in attention and self-awareness, both awake and asleep.
• They tend to be high on the personality trait of "openness to experience", which may simply mean they pay attention to internal states more readily.

None of this means high recallers dream more. They just catch more of what was already happening.

What you can do

If you would like to remember more of your dreams:

• Keep a notebook by the bed. The simple act of intending to record dreams seems to increase recall.
• Stay still and eyes closed for a minute when you wake up. Movement and visual input wipe dream content quickly.
• Write down anything you can hold onto immediately, even fragments. This often unlocks the rest.
• Wake more naturally. Alarm clocks tend to interrupt REM sleep abruptly, which clears the buffer.

If you would like to remember fewer of your dreams, the inverse works. Move quickly, open your eyes, do not think about them.

A deeper question

Why dreams happen at all is still unresolved. Plausible candidates include rehearsal of threat scenarios, consolidation of emotional memory, integration of recent experience with older knowledge, and incidental side-effects of the brain's nightly housekeeping.

Probably it is all of these, plus things we have not yet figured out. The phenomenon is universal across mammals and many birds. It must do something.