It is a common practice for people to sleep on a problem to gain perspective on their situation the following morning. However, new research has claimed that doing so could actually make matters worse. In a study by the University of Massachusetts Amherst, in which 106 young adults were exposed to both upsetting and pleasurable pictures and their reactions examined before and after sleep, it was found that sleeping on a problem in our wooden beds could keep unpleasant memories fresh in our minds upon waking. Lead author of the study Dr Rebecca Spencer explained that the findings relate to the human body's process of evolution, where the retention of painful memories would teach our ancestors not to repeat the actions that resulted in these feelings in the first place. She said of the research: "Some previous studies have looked at just memory itself, not how emotional reactivity changes. When they looked at how our responsiveness changes they have a different and limited measure. "There have been a few studies which look at one or the other but this is the first to look at them side by side."