It is evident that these figures contain inaccuracies, especially in regard to the vertical diameter (where the subsequent two-year period gives a smaller measurement than the preceding) due to the fact that the averages were obtained from an insufficient number of subjects or from subjects differing too widely in intelligence (from schools of different grades). For this reason Binet summarises the differences in growth, that is, the increase in relation to the diameters, under broad groups (six year groups, from four to ten years, and from ten to sixteen), in order to determine whether puberty exerts a sensible influence upon the cranial growth. The result is contained in the following table:
INCREASE OF THE THREE MAXIMUM DIAMETERS OF THE HEAD IN MILLIMETRES FROM FOUR TO EIGHTEEN YEARS OF AGE
| Age in years: from — to — | 4-6; 6-8; 8-10 | 10-12; 12-14; 14-16 | 16-18 |
|---|---|---|---|
| Antero-posterior diameter | 5.6; 0.8; 2.4 | 4.4; 1.8; 5 | 2.1 |
| 8.8 | 11.2 | ||
| Transverse diameter | 1.1; 3.3; 0.7 | 2.2; 3.9; 0.5 | 4.4 |
| 5.1 | 6.6 | ||
| Vertical diameter | 2.8; 0.4; 0.8 | 4.8; 2.3; 2.5 | 0.6 |
| 4.0 | 9.6 |
From which it appears that there exists, in regard to the head, a puberal acceleration of growth.
These conclusions of Binet are indirectly confirmed by the researches of Vitale Vitali regarding the development of the forehead in school-children; since it is well known that the forehead represents the index of the general growth of the cerebral cranium.
Vitale Vitali based his observations upon school-children and students between the ages of ten and twenty. He not only measured the width of the forehead (frontal diameter; see Technique), but also measured its height, obtaining the percentage of its relation to the width (frontal index).
These are his figures:
FRONTAL INDEX AND DIAMETER ACCORDING TO AGE
(Vitale Vitali: Researches Among Scholars and Students From 10 To 20 Years Old)