In the part of this research which was conducted at the Fielden Demonstration Schools, Manchester, the writer was the only supervisor present, and no one was allowed to enter or leave the room while the tests were in progress.

The aim throughout was to secure the most favourable experimental conditions possible, so that the results would afford a reliable estimate of the mental traits under investigation.

Consequently the conditions under which the tests were performed differ very considerably from those of most previous investigators.

Much uncertainty still exists regarding the hierarchical arrange- ment of the coefficients of correlation of each test with every other.

At the present time opinion is about equally divided and it is hoped that the results of this investigation will assist in defining the correct view.