That is, the kind of casual relationships that don’t generally lead to strong emotional bonds, although they tend to be pleasant. Despite the generally negative connotation associated with the word “weak,” the benefits of these relationships can be powerful, indeed. It’s nice to have science confirm something we already know from experience, even though we may not have thought consciously about it. And when the clerk checking out our groceries complains of a sore back from standing too long, we commiserate. She doesn’t care if it’s the mail carrier, the cleaning lady, or a salesman.