Social scientists have made it a priority in recent years to understand upward mobility. Money itself is ... important. Other factors like avoiding eviction, having access to good medical care and growing up in a household with two parents " may also make upward mobility more likely. Now there is another intriguing factor to add to the list, thanks to a study ... in the academic journal Nature: friendships with people who are not poor. "Growing up in a community connected across class lines improves kids' outcome," [said] Raj Chetty ... one of the study's four principal authors. The study ... compares two otherwise similar children in lower-income households " one who grows up in a community where social contacts mostly come from the lower half of the socioeconomic distribution, and another who grows up in a community where social contacts mostly come from the upper half. The average difference between the two, in terms of their expected adult outcomes, is significant. It's the same as the gap between a child who grows up in a family that makes $27,000 a year and one who grows up in a family that makes $47,000. There seem to be three main mechanisms by which cross-class friendships can increase a person's chances of escaping poverty. The first is raised ambition: Social familiarity can give people a clearer sense of what's possible. The second is basic information, such as how to apply to college and for financial aid. The third is networking, such as getting a recommendation for an internship.