Development

That children think differently from adults — not less, but differently — is this folder’s discovery. Piaget turned children’s wrong answers into a research programme and his own three children into the field’s most famous series of observations; Bowlby brought the question of what early separation does out of interpretation and into statistics; and Ainsworth built the twenty-minute procedure with which attachment is measured to this day.

The three files hang together like links in a chain of evidence: Piaget’s child constructs its world, Bowlby’s child needs a secure haven to do so, and Ainsworth’s Strange Situation tests whether it has one. Out of the nursery grew a field with longitudinal studies across decades and meta-analyses across cultures.

For the archive this folder is the friendliest test report of the psychoanalytic neighbourhood: what Anna Freud’s war nurseries observed became here the best-replicated theory of what holds people together.