1) wife
2) parents
3) in-laws
4) children
5) other family members
6) neighbours
7) friends
8) co-workers
9) school chums
10) fellow volunteers
11) members of your social or recreational group

12) religious friends from your church, synagogue, mosque, ashram or cult hideout.

Hate the phone? Face-time with those on the list is perfectly acceptable. Facebook is not.

Do this and you won't catch a cold. Okay, that's not guaranteed, but put it this way: if your social ties are so frayed that you regularly call three or fewer people on that list, you're three times more likely to catch a cold than someone with a diverse set of social ties, someone who would regularly call or talk to people in at least six of those categories.

A man who is socially isolated has a relative risk of death between two and five times greater than one with better social connections. Why that is, scientists don't know. But social isolation is deadly. In France, the leading cause of death among middle-aged men and women is cancer. In the Nineties, a Harvard study of social integration and mortality among French subjects found that the men who were most isolated were 3.6 times more likely to die of cancer than their well-connected peers.

And, like everything else, social class may play a role here, too. The higher yours is, the less vulnerable you are to loneliness.