Marinus van IJzendoorn

Who they are

The first, with Pieter Kroonenberg in 1988, gathered thirty-two Strange Situation samples from eight countries, just under two thousand infants. Security was the most common pattern in every country, which is the finding usually reported. The finding usually left out is that two samples from the same country differed from each other about one and a half times as much as countries differed from each other. One German sample differed from another German sample as much as it differed from an Israeli kibbutz. National attachment profiles are largely an artefact of small unrepresentative samples.

The second, with Marianne De Wolff in 1997, asked whether caregiver sensitivity actually causes security. Across the studies that observed parents and then classified the babies, sensitivity accounts for about six parts in a hundred of the differences. Their own description is moderately strong, with the careful addition that sensitivity is an important but not exclusive condition.

The third, with Marian Bakermans-Kranenburg and Femmie Juffer in 2003, pooled seventy trials of programmes designed to improve the bond. Short, behaviour-focused programmes outperformed long, intensive, insight-oriented ones. Because families were randomly assigned, that is the field's cleanest causal evidence.

He is also a co-author of the disorganised-attachment meta-analysis that established its prevalence, and of the position defending the cross-cultural validity of the Strange Situation against Heidi Keller's challenge.

Key papers

Key papers

van IJzendoorn, M. H., & Kroonenberg, P. M. (1988). Child Development, 59(1), 147-156. Thirty-two Strange Situation samples from eight countries, just under two thousand infants. Security was the most common pattern in every country, which is the part usually reported. The part usually left out is that two samples from the same country differed from each other about one and a half times as much as countries differed from each other, so national attachment profiles are largely an artefact of small unrepresentative samples.

De Wolff, M. S., & van IJzendoorn, M. H. (1997). Child Development, 68(4), 571-591. Second author, and the paper is routinely miscited to him rather than to its first author. Sixty-six studies were gathered and the twenty-one that could answer the question cleanly were separated out. Caregiver sensitivity accounts for about six parts in a hundred of the differences in security, which the authors describe as moderately strong while adding that sensitivity is an important but not exclusive condition.

Bakermans-Kranenburg, M. J., van IJzendoorn, M. H., & Juffer, F. (2003). Psychological Bulletin, 129(2), 195-215. Second author. Seventy randomised trials of programmes designed to improve the parent-infant bond. Short, behaviour-focused programmes outperformed long, intensive, insight-oriented ones, and because families were assigned at random this is the field's cleanest causal evidence.

He is also a co-author of the meta-analysis that established the prevalence of disorganised attachment, and of the position defending the cross-cultural validity of the Strange Situation against Heidi Keller's challenge, set out with Judi Mesman and Abraham Sagi-Schwartz in the third edition of the Handbook of Attachment, 2016.

Key ideas

Pool before concluding. Most of what this field knows reliably, it knows because somebody gathered the studies.

Within-group variation usually beats between-group variation, which is the standard correction to any claim about national character.

Moderate effects, stated as moderate. His papers are unusually careful about how large the effects are not.

Concepts on this site

The Strange Situation

Caregiver Sensitivity

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