The study was published by Oxford University Press on behalf of the Sleep Research Society. The study involved 48 students, with each person sleeping at the laboratory for an overnight sleep evaluation and studied using polysomnography. This comprehensive form of sleep study records the subject's brain waves, blood oxygen level, heart rate, and breathing rate along with eye and leg movements throughout the night.
According to the study's author Erin Wamsley, doctor in cognitive neuroscience and associate professor in psychology and neuroscience, "Humans have struggled to understand the meaning of dreams for millennia... 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."
In the study, participants were woken up to 13 times overnight to report on their experiences. Observations were made during sleep onset, deep REM sleep, and non-REM sleep. On the following morning, participants were asked to identify and describe waking life sources for each of the dreams reported during the night. A total of 481 dream reports were analysed, with some novel and thought-provoking conclusions coming to the foreground.
According to the results of the study, 53.5% of all dreams were traced to a memory, and nearly 50% of reports with a memory source were connected to multiple past experiences. This was mostly expected, with dreams known to extract and manipulate waking memories into novel abstract events. However, the study also found that 25.7% of dreams were related to specific impending events, and 37.4% of dreams with a future event source were additionally related to one or more specific memories of past experiences.
Results from the study are linked to the “episodic future simulation” hypothesis, which says that waking thoughts combine fragments of past episodes into imagined simulations of possible future events. In this way, people can “pre-experience” events by mentally projecting themselves into a possible future. In the study, future-oriented dreams were proportionally more common later in the night, which may be driven by their temporal proximity to the waking events of the following day.
It seems that dreams not only reflect past memories, they may also anticipate probable future events. Future-oriented dreams are very common, and they draw simultaneously from a number of real-life experiences and waking sources. The human brain lies at the intersection of past memories and future likelihoods, with dreams seeming to play an important role in how we anticipate and create real waking events.