Urban density is important. It will also aid social agility since social skills are human skills and if you expect to learn the various types of personalities in the world, time and increased opportunity are factors in the process. A more dense population environment shortens the time span and you will have increased opportunity.  You will see that your sense of personal space in the bank teller line or at the train ticket window will shorten as a matter of local custom.  As the population becomes more dense, there is a lesser expectation of personal space in such waiting lines. There is just less space to waist and you will find that your sense of personal space will decrease accordingly especially after a few polite people ask if you are actually in the line; I mean the cue.