Agreed. If I understood correctly, the recent experiment possibly indicated that socio-economical factors can influence more the future "success" of a subject t

Agreed. If I understood correctly, the recent experiment possibly indicated that socio-economical factors can influence more the future "success" of a subject than other variables, e.g. delayed gratification. The original experiment, by only containing children of the same socio-economical background isolated these variables, and achieved an orthogonal conclusion.