The age-old advice from grandmothers—to sleep over a problem—has just received scientific endorsement. A new study demonstrates that relational memory, the ability to make logical “big picture” inferences from disparate pieces of information, depends on taking a break from studies and learning, and more importantly, getting a good night’s sleep.
Researchers at Beth Israel Deaconess Medical Center and Brigham and Women’s Hospital say that relational memory is a bit like solving a jigsaw puzzle. You have all the pieces and have to fit them together. For instance, if a person learns that A is greater than B and B is greater than C, then he or she knows those two facts. But a third fact—that A is also greater than C—can only be deduced by a process called transitive inference. The researchers hypothesized that this “inferential” knowledge develops during “offline” periods and can be enhanced after a period of sleep.
They tested 56 healthy college students, giving them a problem of patterns to solve. The students were separated into three groups to test their understanding of the “big picture” relationship between individual patterns. Group One was tested after a period of 20 minutes, Group Two was tested after a 12-hour period and Group Three was tested after a 24-hour span. In addition, approximately half of the students in Group Two slept during the 12-hour period, while the other half stayed awake. All the students in Group Three had a full night’s sleep.
The test results showed striking differences among the three groups, especially between students who had slept and those who had stayed awake. Groups Two and Three performed the best, with the students who had had periods of sleep between learning and testing outperforming the others. The implication—sleep is actively engaged in the information processing of our memories. So, the next time you find it difficult to crack a puzzle, sleep over it and see if you fare better.