I believe the answer is: studying before sleeping
Retroactive interference refers to a process when newer information prevent older information from being recalled. Proactive interference refers to the situation when Old information prevent new information from being recalled. Studying before sleeping can reduce the amount of this interference and make new information become more likely to be stored in the memory without any disturbance.
I believe the answer is primary.
Similarities were their geography, religion, temples and technology. Differences are the way they approached death and prepared for the afterlife, their religion, and the Sumerians were one of the first peoples to develop a system of writing.