Nature has effects based on instinct, nurture has its effects based on personality
Sumer most likely developed in Mesopotamia because they were the first to migrate to Mesopotamia, the snow melting provided a water source for the Sumerians, though the Mesopotamian climate isn't very good to flourish in they did create a civilization. The annual flooding from the melted snow deposited silt making the river banks good to plant crops at.
This probably will not help you...
I think the answer is short-term memory.
Hopefully that helped. :D
Sounds like you're doing more than just trying to get a truck to start if ya know whata mean ;)