Understanding friendships, your own included

The death of a spouse is one of the transitions most studied by life-course research. Surveys describe a reshaping of relationships rather than a simple withdrawal.

Do exchanges between friends follow a rule of return? Since the late 1970s, social psychology has distinguished two ways of keeping accounts in a relationship.

Georg Simmel described the modern individual as the point where independent social circles intersect. The idea has been taken up and formalised, but it remains hard to measure.

Personal networks are strongly homogeneous in age. Relationships crossing that barrier have particular properties and are little studied.

The share of single-person households has doubled in half a century in rich countries. Its association with measured isolation is weaker than assumed.

Reporting few friends or saying one is lonely has a social cost. Methods that bypass that cost give noticeably different results.

The difficulty is real and measurable. It stems not from a personal disposition but from the disappearance of one precise kind of situation.

Confiding is the criterion defining the narrowest circle in most measurement instruments. What it produces has been studied mainly in the laboratory.

The result is old, robust, and it still surprises. It stems less from a misunderstanding than from what the word covers.

It is not an impression, it is a theorem. Proved in 1991, it follows from how a network is sampled when one follows its ties.

It is one of the strongest regularities in social graphs. It explains why networks close in on themselves without anyone deciding so.

Formulated in 1954, it holds that mixing between groups reduces prejudice. The conditions it sets are more demanding than its uptake suggests.

Changing city does not erase relationships, it changes their nature. Longitudinal surveys show faster than average replacement.

European surveys allow reported contact frequency to be compared. What those comparisons measure is less obvious than it seems.