The colony contained about 500 breeding pairs and, averaged over the study's two years, herons caused the failure of 169 nests a year at the colony's centre, but only 92 a year at its edge.

ECONOMIST: Animal behaviour

The study looked at 1, 255 pairs of mothers and children from 1999 to 2002.

BBC: C-section 'may double risk of childhood obesity'

Mr Plomin has also set up a study working with 10, 000 pairs of identical and non-identical twins in Britain.

ECONOMIST: WHAT WE LEARN FROM TWINS