Sleep on It

Dreams of a task being learnt improve performance, suggesting that they may be by-products of memory processing.

Sleep on it, goes the advice, and a solution to the problem will come to you. It may seem clichéd, but there is truth in the advice. This is how the authors of a paper in Current Biology have summarised their findings: subjects were tested on a virtual navigation task and then re-tested on the same task five hours later. Improved re-test performance was strongly associated with task-related dream imagery during an intervening afternoon nap. Task-related thoughts during wakefulness, in contrast, did not predict improved performance. These observations suggest that sleep-dependent memory consolidation is facilitated by the offline reactivation of recently formed memories, and furthermore, that dream experiences reflect this memory processing. That similar effects were absent during wakefulness suggests that these mnemonic processes are specific to the sleep state.

Of the 99 people tested on a virtual 3-D maze, four who reported dreaming about the task, performed so much better—improving their performance tenfold—that the scientists concluded that the dreams of these subjects actually helped in the consolidation of performance related memory. While by now it was well known that sleep helps consolidate memory, it was not clear which memories were consolidated and how dreaming helped the process. This paper radically revises the previous understanding, and in fact one of the co-authors, Robert Stickgold of Harvard Medical School, has been quoted as saying, “I was startled by this finding. Task-related dreams may get triggered by the sleeping brain’s attempt to consolidate challenging new information and to figure out how to use it.”

The suggestion then is that dreams may not directly help consolidate memories, but may be a by-product of the process of consolidation of memories. In other words, the fact that only four of the subjects dreamed of the maze would suggest that they were using ‘offline processing’ or sleep time to consolidate their earlier learning. So, the next time you start analysing your dreams, you may need to consider not what it says about your life when you are awake, but what it says about your life when you are asleep.

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