Since childhood we have been advised by the to study or revise the assignments early morning. But the recent studies indicate that level of stress hormones is highest at the time of wakening. Stress hormones affect memory negatively. As the cortisol level is the highest in the morning just after awakening (in day workers)  and because the excess of cortisol can impair the ability of the hippocampus to both encode and recall memories, thus it is hypothesised that morning time may not be the best time to study and revise assignments..