One of sleep’s functions is facilitating learning. Have you ever learned something new one day and then dreamed about it later that night? Another study finds further connections. From Scientific American:
Scientists had more than 200 subjects memorize related words like “fire and smoke,” or unrelated word pairs like “insect and truth.” Some studied the words at 9 am, others at 9pm.
The researchers tested the subjects’ ability to remember the pairs after 30 minutes, 12 hours or 24 hours.
Sleep had little effect on the ability to recall related words. But subjects who slept between tests were significantly better at remembering the unrelated words than those who got no shuteye.
For more info check out the original research article on PLoS One.