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How Yesterday and Tomorrow Intertwine When We Dream

Dreaming helps our minds anticipate future events based on previous experiences.

Key points

  • Dream research often focuses on how nightly dreams facilitate learning and memory encoding based on past experiences.
  • A new study focuses on how dreaming may also help us prepare for anticipated events happening tomorrow or in the near future.
  • This study suggests that about one quarter (25.7%) of nightly dreams construct a future-oriented narrative, a.k.a. "episodic future simulation."
Source: aslysun/Shutterstock

Each night when we dream, new research suggests that our minds create future-oriented fantasies and narratives that help us prepare for anticipated events happening tomorrow or soon thereafter. Over a third (37.4%) of these forward looking dreams incorporate specific memories from someone's past.

This novel dream research (Wamsley, 2021) was presented virtually at this year's annual SLEEP 2021 meeting, June 10-13. The findings appear as an online abstract in the peer-reviewed journal Sleep.

How Does Dreaming Help Us Construct Simulations of the Future?

"The 'episodic future simulation' hypothesis proposes that waking thought combines fragments of various past episodes into imagined simulations of events that may occur in the future," first author Erin Wamsley, associate professor of psychology and cognitive neuroscientist at Furman University, writes in the paper's abstract.

For this study, Wamsley and colleagues recruited four dozen students (N = 48) to test their hypothesis that "dreams focused on future events utilize memories of multiple past experiences."

Each study participant spent a night in the sleep lab equipped with polysomnography equipment. While being evaluated, participants were woken up multiple times and asked to self-report their experiences and describe any dreams during sleep onset, rapid eye movement (REM) sleep, and non-REM sleep. The next morning, they were asked to recount each dream they'd reported the previous evening. All told, 481 "dream reports" were analyzed.

About 25% of Nightly Dreams Anticipate What's Happening Tomorrow

Wamsley's results show that 53.5% of nighttime dreams could be traced to a specific memory associated with past experiences. Dreaming seemed to combine "fragments of multiple life experiences" in a way that influenced various hypothetical scenarios of what might play out in the near future.

Of the 25.7% of dreams that focused on "specific impending future events," a large portion incorporated one or more specific memories from the past. Interestingly, future-oriented dreams were more likely to occur later in the night or towards the end of someone's sleep cycle.

"The proportional increase of future-oriented dreams later in the night may be driven by temporal proximity to the events of the following day," Wamsley explains. "While these dreams rarely depict future events realistically, the activation and recombination of future-relevant memory fragments may nonetheless serve an adaptive function."

Memory-Based Dreams May Optimize How We Respond to Similar Situations in the Future

"Humans have struggled to understand the meaning of dreams for millennia," Wamsley said in a June 8 news release. "We present new evidence that dreams reflect a memory-processing function. Although it has long been known that dreams incorporate fragments of past experience, our data suggest that dreams also anticipate probable future events."

"[Episodic future simulation] is a new description of how dreams draw simultaneously from multiple waking-life sources, utilizing fragments of past experience to construct novel scenarios anticipating future events," she concludes.


Erin Wamsley. "Dreaming as Constructive Episodic Future Simulation." Sleep (First published online: May 03, 2021) DOI: 10.1093/sleep/zsab072.033

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