According to a Harvard study where one group of students received normal sleep over a four-day period and another was sleep deprived over a four-day period, lack of sleep caused the second group to perform worse on tests. The researchers attributed this to the affects of sleep deprivation on the cortex, the information storage area of the brain. Colin Bamford, who directs the University of Arizona neurophysiology and sleep lab, was not surprised by these results. He said, "Every study to date has shown that, and I would expect this one to mirror the others."
A study published in the University of Minnesota Undergraduate Journal of Psychology in 2009 found that cramming did not improve test performance. Depending on the individual and his or her learning capabilities, the possibility existed that the crammer would do as well as the non-crammer, but there are a number of factors that go into that. For instance, the study used a rote memorization exam that did not require any analysis, evaluation or creation. According to Bloom's Taxonomy of Learning, these three tasks require the highest levels of thinking to perform, so a test that used these skills may prove more difficult for a crammer.
One part of taking a test is knowing the information and having the ability to apply it, but the other part is knowing how to take a test. For instance, knowing what to do if you don't know an answer or if the problems are worth different points, and knowing what parts of the test to tackle first. The sleep deprivation that comes with cramming affects reaction time and decision-making skills. Not to mention the potential reliance on caffeine, which can lead to nervousness, upset stomach and restlessness.
Murray Glanzer and Anita R. Cunitz of New York University's Institute for Behavioral Research conducted two studies which showed that when given a list of facts, people tend to remember what's at the beginning of the list or what's at the end of it. When studying happens at the last minute, the material becomes a list of facts, so if cramming is necessary, try studying the most important information at the beginning.