There is an extensive literature upon this question, the tendency of which is to decide it affirmatively.
Parchappe has made a comparative study between writers of recognized ability and simple manual workers, and has found that the former have a development of the head notably in excess of the latter.
Broca took measurements, in various hospitals, of the heads of physicians and male nurses, and found a greater development of head in the case of the physicians.
Lebon made a study of cranial measurements in men of letters, tradesmen, the nobility and domestic servants, and found the maximum development among the men of letters and the minimum among the servants. The tradesmen, who at all events are performing a work of social utility, stand next to the men of letters; while the aristocrats show some advantage over the domestics. Bajenoff took his measurements from famous persons on the one hand and from convicted assassins on the other, and found a greater head development among the former.
Enrico Ferri has made similar researches among soldiers who have had a high-school education and those who are uneducated, and has found a more developed cranium among the educated soldiers.
I also have made my own modest contribution to this important question, by seeking to determine the difference in cranial volume between the school-children who stand respectively at the head and foot of their class, and have found among children of the age of ten a mean cranial circumference of 527 millimetres for the more intelligent and of only 518 millimetres for the less intelligent.
Similar results were obtained by Binet in his researches among the elementary schools of Paris. He found among children of the age of twelve that the brightest had a mean cranial circumference of 540 millimetres and those at the foot of their class a mean of only 530 millimetres. The following table gives a parallel between these various cranial measurements:
CRANIAL MEASUREMENTS (in Millimetres)[39]
Binet Children in the elementary schools of Paris, from 11 to 13 years of age
Montessori Children in the elementary schools of Rome, from 9 to 11 years of age