The difference between a friend and a close friend can be measured in hours.
That's the conclusion of a professor at the University of Kansas who has quantified how much time it takes to build a true friendship, as opposed to a mere acquaintance.
"We have to put the time in," said Jeffrey Hall, an associate professor of communication studies. "You can't snap your fingers and make a friend. Maintaining close relationships is the most important work we do in our lives — most people on their deathbeds agree."
Hall's research indicates two people need to spend roughly 50 hours with each other to go from being an acquaintance to a casual friend.
To move beyond that to a real friend requires about 90 hours.
And to establish a truly close friendship two people generally need to spend more than 200 hours together.
Hall reached these conclusions in two stages.
First, he looked at 355 responses to an online survey from people who had relocated within the past six months and were seeking out new friends. The survey asked about people the respondents had met, how much time they had spent together and how close the new friendship had become.
Next, Hall surveyed 112 freshmen at KU who had recently moved to Lawrence. He asked them about people they had met at the beginning of the school year and then followed up at four and seven weeks later to see how those relationships had developed.
"When people transition between stages, they'll double or triple the amount of time they spend with that other person in three weeks' time," Hall said in a university press release. "I found freshmen who spent one-third of all waking hours in a month with one good friend."
Hall's work was recently published in the Journal of Social and Personal Relationships.
Hall and a colleague developed an online questionnaire to test the closeness of a relationship with someone who is not a potential romantic partner.
"You can't make people spend time with you, but you can invite them," Hall said. "Make it a priority to spend time with potential friends. If you are interested in a friendship, switch up the context. If you work together, go to lunch or out for a drink. These things signal to people that you are interested in being friends with them."