relies on people’s tendency to be drawn to novelty as a way to increase the depth of her new friendships quickly.

I had thought that they might represent something like acquaintances (people you are familiar with, many of whom you probably work with, at around 500)

you could become “good friends” if you spend 120-160 hours together over three weeks, and “best friends” if you spend 200 hours together over six weeks.

quality of a friendship depends directly on the time we invest in