Marked differences between the groups were shewn. The intellectual capacity was represented by figures as follows:—
| Group 1 | 125 |
| Group 2 | 118 |
| Group 3 | 107 |
| Group 4 | 92 |
A further research of 548 children, grouped according to the occupation of their father, gave its results in terms of the percentage of children in each group who scored a mark higher than the median for the whole 548. They are as follows:—
| Professional group | 85% |
| Executive group | 68%. |
| Artisan group | 41% |
| Labour group | 39% |
In the "Journal of Educational Psychology," Vol. IX, 1916, Mr. A.W. Kornhauser gives evidence from the examination of 1,000 children drawn from five schools in Pittsburgh.
Schools A and B were attended by children of unskilled manual workers.
Schools C and D by children of skilled artisans and small shopkeepers.
School E by children of parents in very comfortable circumstances.
The results are tabulated as—
Retarded, i.e., below average.