All we need for effective learning is well-structured sleep at the right time and of the optimum length. Many individuals sleep less than 5 hours and wake up refreshed. Many geniuses sleep little and practice catnaps. Long sleep may correlate with disease. This is why mortality studies show that those who sleep 7 hours live longer than 9-hour-sleepers. The best formula for good sleep: listen to your body. Go to sleep when you are sleepy and sleep as long as you need. When you catch a good rhythm without an alarm clock, your sleep may ultimately last less but produce far better results in learning. It is the natural healthy structure of sleep cycles that makes for good learning (esp. in non-declarative problem solving, creativity, procedural learning, etc.). It is not true that if your sleep is short, so is your memory