The second, and related, problem is that some of the asset classes were quite small.

ECONOMIST: Spreading the risk has spread the losses

However, one problem has been that some of the research has struggled to identify whether the findings were related to the fact that mothers from more affluent backgrounds were more likely to breastfeed and it was factors related to the family circumstances that was really influencing intelligence.

BBC: Breastfeeding 'helps to boost IQ'