Since it was in the 50's we really have no idea just how statistically accurate this study is. For example, they may not have had a equal spread of income levels. Most of the participants may have been poor and there may have been only one or two high income families involved. Such a small sample would not give reliable results. However if the study did have an accurate cross sample of incomes, then perhaps the results indicate that some sort of education program is in order for children in well to do families.
Plenty of first-class science and engineering was done in the 1950s and before. The 50s produced hydrogen bombs, supersonic aircraft, and great advances in chemotherapy and computer science, for example. They were quite capable of doing an empirical study to a standard we would recognize.
