I haven’t done a scientific study, but results over the years have indicated to me that people who are introduced and assimilated into a work culture immediately upon hire stay longer, are more productive, and more successful longterm.
From my experience and those of my management peers, employees who spend time with their direct supervisor, co-workers and key players in the organization within the first day or week of employment tend to stay with the organization and be more productive.
One place I worked, my new boss took me to lunch on my first day; another, it was the first week. Every place I have worked has involved this type of indocrinization.
How can this be applied elsewhere? Whether its your students, your employees, or your social group, going out of your way to make sure the new kid on the block feels like they know their role and how they will interact with others is the right thing to do.
Take time out with every new person, and you will spend less time out recruiting to replace them later on.