From the article: "A little more than 10 years ago, the evolutionary
psychologist Robin Dunbar began a study of the Christmas-card-sending habits of
the English. This was in the days before online social networks made friends
and “likes” as countable as miles on an odometer, and Dunbar wanted a proxy for
meaningful social connection. He was curious to see not only how many people a
person knew, but also how many people he or she cared about. The best way to
find those connections, he decided, was to follow holiday cards. After all,
sending them is an investment: You either have to know the address or get it;
you have to buy the card or have it made from exactly the right collage of
adorable family photos; you have to write something, buy a stamp, and put the
envelope in the mail. These are not huge costs, but most people won’t incur
them for just anybody." Read more
