Problem:
The only purpose for sleeping is to reduce travel weariness. That's something that alcoholic beverages and drugs can already do. Beds don't offer anything unique nor do they get enough attention they deserve.
Idea:
After you wake up from sleeping, you should get the "Open Mind" buff. The duration of the buff should be based on how many hours you sleep. For example, sleeping for one hour should make the buff last for one minute. The buff should also be capped at a certain duration, like 1 hour which would be 2.5 days of sleep. Anything over 2.5 days of sleep, will not improve the open mind buff that you will acquire when you log in. The idea is that a well rested mind will wake up refreshed, allowing for better studying.
Affect:
The open mind buff will make curiosities be learned faster by 15% or less. It will only be in affect when the player is logged in.