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Letters to the Editor
December 1, 2008

Breastfeeding, Breast-Milk Feeding, Breast Feeding, and IQ: Unknown and Known Knowns

Arch Gen Psychiatry. 2008;65(12):1457-1458. doi:10.1001/archpsyc.65.12.1457

The Promotion of Breastfeeding Intervention Trial (PROBIT) Study Group1 is to be congratulated on acquiring much new data on the important but neglected topic of breastfeeding and IQ. However, as well as the known unknowns, the unknown knowns need just as much attention. The literature review (for which none of the authors took responsibility!) omitted many pertinent facts that would have simplified interpretation of their results. A major obstacle to scientific progress, especially in this field, is the known knowns, “what you know for sure that ain't so” (Mark Twain). Myths kill. Crucially, Donald Rumsfeld ignored known knowns! The mechanical sompe theory2 was designed to explain why certain serious infections were more common in nonbreastfed infants, but it covers a wider field and explains otherwise odd findings.1 It has also led to a critical evaluation of competing beliefs.