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Dreaming About a Task Is Associated with Better Memory

A recent study finds that subjects who dream about an image remember it better.

A recent paper published in Scientific Reports shows that dreaming of a visual learning task is associated with improved post-sleep memory performance (Plailly et al., 2019). This study follows several others that have recently attempted to show a link between learning and dreams, with varying success. (See previous posts: Dreaming of a task associated with improved performance; More evidence that dreams reflect learning during sleep; and Practicing darts in lucid dreams improves performance).

Waking life experiences are frequently incorporated into dreams at night, especially the night following an experience, coined the ‘Day-residue’ by Freud. As knowledge has grown about the importance of sleep for learning and strengthening memory, the possible link between dreaming and learning has been explored. The authors of the current study used a novel paradigm to test this hypothesis, in which participants explored multisensory visual landscapes over the course of a few days, while also recording their dreams, and subsequently were tested on their memory for the landscapes.

Specifically, over 3 days, participants explored a particular visual landscape on a computer screen (a desert, coastal cliff, and lavender field) which was populated by ‘scented’ areas denoted by small yellow circles. When participants clicked on a circle, specific odors would be released, as if that particular area of the landscape emitted a certain odor. Participants spent 7 minutes exploring a landscape and its odors each day, but without being told that they would later be tested on their memory for these landscapes.

In total, 32 participants took part, all of whom regularly remembered their dreams (at least 4 dreams recalled per week). For 3 nights these participants wore a home sleep-monitoring device (a wrist actimeter) and they reported their dreams at 5 am and on their final morning awakening, using a voice recorder.

In the morning they filled in a questionnaire about the content of the night’s dreams, including reporting whether the dream was related to their recent waking life experiences (such as the task/experiment). Judges also independently rated the dreams on the extent to which they incorporated elements related to the task and the experiment.

Following these nights, participants were tested on their memory for the three landscapes. They were tested on whether they remembered which odors had been presented (compared to novel odors that had not been presented previously); they were also tested on where in the landscape they thought each odor had been presented, and finally, regardless of the specific odor, they were tested on whether they remembered where the yellow circles had been in each landscape.

In total, 16 participants reported dreams containing elements related to the task, including odors, elements of the landscapes (e.g., cliffs, beach, sea), or the yellow circles.

  • “I was at the top of a cliff. It was really resembling the one I saw in the lab yesterday.”
  • “I was swimming in the sea, there were waves…on the beach I saw an old pair of glasses made out of metal and with curved branches to go around the ears…I scratch my nose and three boogers got out of it, they looked like little characters with a corn seed shape.”
  • "A yellow circle associated with the word lemon."

There were an additional 5 participants who reported dreams related to the experiment more generally, such as:

  • “I dreamt that I woke up to report my dream using the voice recorder just as in the experiment.”
  • “I was in the building for the study of dreams, downstairs in the cafeteria, and I was explaining to a rhinoceros that I was preparing my dreams as my hand-bags, with many objects which could be useful in case.”
  • “Some guys with white coats were doing experiments on us.”

The authors found that participants with learning-related dreams (n = 16) and participants with learning-related and/or experiment-related dreams (n = 21) had significantly better memory for the location of the yellow circles in the landscapes in comparison to the other participants. However, there was no difference with regard to memory for the actual scents or the context for the scents.

The authors claim "our results support the hypothesis that the learning phase is loosely incorporated into dreams and that this incorporation is associated with sleep-related memory consolidation."

References

Plailly, J., Villalba, M., Vallat, R., Nicolas, A., & Ruby, P. (2019). Incorporation of fragmented visuo-olfactory episodic memory into dreams and its association with memory performance. Scientific reports, 9(1), 1-14.

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