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How often do you remember your dreams? For some people the answer can be as little as once or twice a month, whereas others can recollect their sleeping thoughts almost every day.

Little is known about what causes people to remember dreams, but


a new study has linked a propensity to remember dreams to a stronger neurological reaction to hearing the sound of first names -- both when you're awake and asleep.

Researchers at the Lyon Neuroscience Research Centre divided 36 subjects into two groups -- high dream recallers who frequently remembered their mental nighttime escapades, and low dream recallers who only remembered their dreams once or twice a month.

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For every participant, brain activity that occurred when they heard their first name and an unfamiliar first name was recorded both during sleep and while they were awake.

The methodology was chosen as the study relied on forcing the brain to process some kind of information, and as people process the sound of their first names on a daily basis, they are used to responding to it, Perrine Ruby, a neuroscientist who co-authored the study, told Wired.co.uk.


This approach was first used in a study that was published in January, as well as in the more recent study, conducted by the same research team and published in Frontiers in Psychology.

The newer study measured the oscillation activity of brain waves and discovered that high recallers exhibited a deeper processing of complex sounds, which supported the hypothesis of neurophysiological trait differences in high and low dream recallers.

Researchers had anticipated that high dream recallers might well have stronger responses to hearing the names while they were sleeping, but did not expect to discover that they also exhibited stronger reactions during wakefulness. "What we saw is that during wakefulness, high recallers are more reactive to the environment than low recallers. The brainwave associated with attention orienting is larger in the high recallers, as if they are much more attracted and attentive to the external environment. Low recallers had a smaller wave, which could be associated with a greater ability to be consumed by a task and resistant to interferences. So it's two different ways [of processing information], which may have advantages according to the context," says Ruby.

High recallers were also discovered to experience more intra-sleep wakefulness -- about 30 minutes per night -- than low recallers who on average experienced around half this amount. Both of these fall within the normal range for the amount of disturbance people experience during their complex nightly sleep patterns, but it does suggest that high recallers are more likely to respond to stimuli around them at night.

Overall, the results suggest that the functional organisation of the way the brain processes information is different in each group, both during wakefulness and sleep. Greater brain reactiveness during sleep causes high recallers to wake more frequently, "facilitating the encoding of the dream in memory".


One of the obstacles in determining why some people remember more dreams than others is that there is still no way of telling for sure exactly whether people can't recall dreams because of their memories, or because they haven't been dreaming at all. "Some subjects do remember much more about their dreams than others, but in addition to this, maybe there is also an issue of production," says Ruby. "What we lack is some kind of neurophysiological marker of dreaming. We only have dream reports, so we do not know and the subject cannot tell while he is dreaming."

The science of dreaming still remains something of a mystery to us, and while there are many theories of what causes us to dream and what function dreams serves, none of the hypotheses can be proved until we can first identify how to measure when we are dreaming.

This article was updated with minor clarifications on 16 August.