The widespread interest in vocational psychology which has grown up in recent years, the eagerness with which even the most superficial and absurd systems of "character analysis" are being adopted and tried out, and especially the lack of references, offering conservative evaluation, to which inquirers may be directed, have made it seem advisable to publish the material in systematic form.

The book is essentially a presentation of the problems and methods of that branch of applied psychology which deals with individual differences in mental constitution. In the present instance only those differences are considered which may seem to be significant in determining the individual's choice of a vocation, or in influencing the selection of workers from among a group of applicants or candidates.

It is the writer's hope that the book may be suggestive to the individual who seeks to know himself better, helpful to the student and parent who may desire to avoid the wiles of the charlatan, encouraging to the investigator or counsellor who is engaged in carrying forward the solution of vocational problems, and useful to the practical man who may be mainly interested in surrounding himself with competent associates and employees.